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  • Ballistic Majorana nanowire devices
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-15
    Önder Gül, Hao Zhang, Jouri D. S. Bommer, Michiel W. A. de Moor, Diana Car, Sébastien R. Plissard, Erik P. A. M. Bakkers, Attila Geresdi, Kenji Watanabe, Takashi Taniguchi, Leo P. Kouwenhoven

    Majorana modes are zero-energy excitations of a topological superconductor that exhibit non-Abelian statistics1,2,3. Following proposals for their detection in a semiconductor nanowire coupled to an s-wave superconductor4,5, several tunnelling experiments reported characteristic Majorana signatures6,7,8,9,10,11. Reducing disorder has been a prime challenge for these experiments because disorder can mimic the zero-energy signatures of Majoranas12,13,14,15,16, and renders the topological properties inaccessible17,18,19,20. Here, we show characteristic Majorana signatures in InSb nanowire devices exhibiting clear ballistic transport properties. Application of a magnetic field and spatial control of carrier density using local gates generates a zero bias peak that is rigid over a large region in the parameter space of chemical potential, Zeeman energy and tunnel barrier potential. The reduction of disorder allows us to resolve separate regions in the parameter space with and without a zero bias peak, indicating topologically distinct phases. These observations are consistent with the Majorana theory in a ballistic system21, and exclude the known alternative explanations that invoke disorder12,13,14,15,16 or a nonuniform chemical potential22,23.

    更新日期:2018-01-15
  • Strain distributions and their influence on electronic structures of WSe2–MoS2 laterally strained heterojunctions
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-15
    Chendong Zhang, Ming-Yang Li, Jerry Tersoff, Yimo Han, Yushan Su, Lain-Jong Li, David A. Muller, Chih-Kang Shih

    Monolayer transition metal dichalcogenide heterojunctions, including vertical and lateral p–n junctions, have attracted considerable attention due to their potential applications in electronics and optoelectronics. Lattice-misfit strain in atomically abrupt lateral heterojunctions, such as WSe2–MoS2, offers a new band-engineering strategy for tailoring their electronic properties. However, this approach requires an understanding of the strain distribution and its effect on band alignment. Here, we study a WSe2–MoS2 lateral heterojunction using scanning tunnelling microscopy and image its moiré pattern to map the full two-dimensional strain tensor with high spatial resolution. Using scanning tunnelling spectroscopy, we measure both the strain and the band alignment of the WSe2–MoS2 lateral heterojunction. We find that the misfit strain induces type II to type I band alignment transformation. Scanning transmission electron microscopy reveals the dislocations at the interface that partially relieve the strain. Finally, we observe a distinctive electronic structure at the interface due to hetero-bonding.

    更新日期:2018-01-15
  • Metagenomic analysis of microbial communities yields insight into impacts of nanoparticle design
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-15
    Jacob W. Metch, Nathan D. Burrows, Catherine J. Murphy, Amy Pruden, Peter J. Vikesland

    Next-generation DNA sequencing and metagenomic analysis provide powerful tools for the environmentally friendly design of nanoparticles. Herein we demonstrate this approach using a model community of environmental microbes (that is, wastewater-activated sludge) dosed with gold nanoparticles of varying surface coatings and morphologies. Metagenomic analysis was highly sensitive in detecting the microbial community response to gold nanospheres and nanorods with either cetyltrimethylammonium bromide or polyacrylic acid surface coatings. We observed that the gold-nanoparticle morphology imposes a stronger force in shaping the microbial community structure than does the surface coating. Trends were consistent in terms of the compositions of both taxonomic and functional genes, which include antibiotic resistance genes, metal resistance genes and gene-transfer elements associated with cell stress that are relevant to public health. Given that nanoparticle morphology remained constant, the potential influence of gold dissolution was minimal. Surface coating governed the nanoparticle partitioning between the bioparticulate and aqueous phases.

    更新日期:2018-01-15
  • Electrical control of charged carriers and excitons in atomically thin materials
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-15
    Ke Wang, Kristiaan De Greve, Luis A. Jauregui, Andrey Sushko, Alexander High, You Zhou, Giovanni Scuri, Takashi Taniguchi, Kenji Watanabe, Mikhail D. Lukin, Hongkun Park, Philip Kim

    Electrical confinement and manipulation of charge carriers in semiconducting nanostructures are essential for realizing functional quantum electronic devices1,2,3. The unique band structure4,5,6,7 of atomically thin transition metal dichalcogenides (TMDs) offers a new route towards realizing novel 2D quantum electronic devices, such as valleytronic devices and valley–spin qubits8. 2D TMDs also provide a platform for novel quantum optoelectronic devices9,10,11 due to their large exciton binding energy12,13. However, controlled confinement and manipulation of electronic and excitonic excitations in TMD nanostructures have been technically challenging due to the prevailing disorder in the material, preventing accurate experimental control of local confinement and tunnel couplings14,15,16. Here we demonstrate a novel method for creating high-quality heterostructures composed of atomically thin materials that allows for efficient electrical control of excitations. Specifically, we demonstrate quantum transport in the gate-defined, quantum-confined region, observing spin–valley locked quantized conductance in quantum point contacts. We also realize gate-controlled Coulomb blockade associated with confinement of electrons and demonstrate electrical control over charged excitons with tunable local confinement potentials and tunnel couplings. Our work provides a basis for novel quantum opto-electronic devices based on manipulation of charged carriers and excitons.

    更新日期:2018-01-15
  • Tunable confinement of charges and excitations
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-12
    Deep Jariwala

    Tunable confinement of charges and excitations Tunable confinement of charges and excitations, Published online: 12 January 2018; doi:10.1038/s41565-017-0047-1 Electrical control over quantum confinement opens a new avenue for spatial manipulation of charge carriers and bound excited states for quantum opto-electronics.

    更新日期:2018-01-15
  • Solid-state synthesis
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Wenjie Sun

    Solid-state synthesis Solid-state synthesis, Published online: 09 January 2018; doi:10.1038/s41565-017-0056-0 Solid-state synthesis

    更新日期:2018-01-09
  • Quantum search on a single-atom qudit
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Andrea Morello

    Quantum search on a single-atom qudit Quantum search on a single-atom qudit, Published online: 09 January 2018; doi:10.1038/s41565-017-0049-z A terbium-based molecular magnet, containing four nuclear quantum states, or a qudit, experimentally validates the Grover algorithm for database searches.

    更新日期:2018-01-09
  • Bigger and cheaper
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09

    Bigger and cheaper Bigger and cheaper, Published online: 09 January 2018; doi:10.1038/s41565-017-0054-2 Scalability and cost efficiency should intensify research efforts in DNA nanotechnology.

    更新日期:2018-01-09
  • No waste and no salt
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Adam Weingarten

    No waste and no salt No waste and no salt, Published online: 09 January 2018; doi:10.1038/s41565-017-0057-z No waste and no salt

    更新日期:2018-01-09
  • Research, discovery and failure
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Deji Akinwande

    Research, discovery and failure Research, discovery and failure, Published online: 09 January 2018; doi:10.1038/s41565-017-0048-0 Failure is an unavoidable element of the process that leads to discovery and it should be embraced even in early education, says Deji Akinwande.

    更新日期:2018-01-09
  • T-cell magnetic drive
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Chiara Pastore

    T-cell magnetic drive T-cell magnetic drive, Published online: 09 January 2018; doi:10.1038/s41565-017-0055-1 T-cell magnetic drive

    更新日期:2018-01-09
  • Nano-opto-electro-mechanical systems
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Leonardo Midolo, Albert Schliesser, Andrea Fiore

    A new class of hybrid systems that couple optical, electrical and mechanical degrees of freedom in nanoscale devices is under development in laboratories worldwide. These nano-opto-electro-mechanical systems (NOEMS) offer unprecedented opportunities to control the flow of light in nanophotonic structures, at high speed and low power consumption. Drawing on conceptual and technological advances from the field of optomechanics, they also bear the potential for highly efficient, low-noise transducers between microwave and optical signals, in both the classical and the quantum domains. This Perspective discusses the fundamental physical limits of NOEMS, reviews the recent progress in their implementation and suggests potential avenues for further developments in this field.

    更新日期:2018-01-09
  • Reality, fantasy and civility in molecular assemblers
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-09
    Chris Toumey

    Reality, fantasy and civility in molecular assemblers Reality, fantasy and civility in molecular assemblers, Published online: 09 January 2018; doi:10.1038/s41565-017-0050-6 Chris Toumey revisits the 2003 exchange of opinions between Eric Drexler and Richard Smalley, which was one of the most colourful disagreements in the history of nanotechnology.

    更新日期:2018-01-09
  • An adaptive supramolecular hydrogel comprising self-sorting double nanofibre networks
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-08
    Hajime Shigemitsu, Takahiro Fujisaku, Wataru Tanaka, Ryou Kubota, Saori Minami, Kenji Urayama, Itaru Hamachi

    Novel soft materials should comprise multiple supramolecular nanostructures whose responses (for example, assembly and disassembly) to external stimuli can be controlled independently. Such multicomponent systems are present in living cells and control the formation and break-up of a variety of supramolecular assemblies made of proteins, lipids, DNA and RNA in response to external stimuli; however, artificial counterparts are challenging to make. Here, we present a hybrid hydrogel consisting of a self-sorting double network of nanofibres in which each network responds to an applied external stimulus independent of the other. The hydrogel can be made to change its mechanical properties and rates of release of encapsulated proteins by adding Na2S2O4 or bacterial alkaline phosphatase. Notably, the properties of the gel depend on the order in which the external stimuli are applied. Multicomponent hydrogels comprising orthogonal stimulus-responsive supramolecular assemblies would be suitable for designing novel adaptive materials.

    更新日期:2018-01-08
  • Fast and pure
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-01
    Silvano De Franceschi

    Fast and pureFast and pure, Published online: 01 January 2018; doi:10.1038/s41565-017-0045-3Removing nuclear spins by means of isotopically purified silicon, and introducing magnetic field gradients by means of microfabricated ferromagnets yields electron spin qubits with enhanced fidelity and fast electrical control.

    更新日期:2018-01-01
  • Synthetic oligorotaxanes exert high forces when folding under mechanical load
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-01
    Damien Sluysmans, Sandrine Hubert, Carson J. Bruns, Zhixue Zhu, J. Fraser Stoddart, Anne-Sophie Duwez

    Folding is a ubiquitous process that nature uses to control the conformations of its molecular machines, allowing them to perform chemical and mechanical tasks. Over the years, chemists have synthesized foldamers that adopt well-defined and stable folded architectures, mimicking the control expressed by natural systems1,2. Mechanically interlocked molecules, such as rotaxanes and catenanes, are prototypical molecular machines that enable the controlled movement and positioning of their component parts3,4,5. Recently, combining the exquisite complexity of these two classes of molecules, donor–acceptor oligorotaxane foldamers have been synthesized, in which interactions between the mechanically interlocked component parts dictate the single-molecule assembly into a folded secondary structure6,7,8. Here we report on the mechanochemical properties of these molecules. We use atomic force microscopy-based single-molecule force spectroscopy to mechanically unfold oligorotaxanes, made of oligomeric dumbbells incorporating 1,5-dioxynaphthalene units encircled by cyclobis(paraquat-p-phenylene) rings. Real-time capture of fluctuations between unfolded and folded states reveals that the molecules exert forces of up to 50 pN against a mechanical load of up to 150 pN, and displays transition times of less than 10 μs. While the folding is at least as fast as that observed in proteins, it is remarkably more robust, thanks to the mechanically interlocked structure. Our results show that synthetic oligorotaxanes have the potential to exceed the performance of natural folding proteins.

    更新日期:2018-01-01
  • Fast water transport in graphene nanofluidic channels
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-01
    Quan Xie, Mohammad Amin Alibakhshi, Shuping Jiao, Zhiping Xu, Marek Hempel, Jing Kong, Hyung Gyu Park, Chuanhua Duan

    Superfast water transport discovered in graphitic nanoconduits, including carbon nanotubes and graphene nanochannels, implicates crucial applications in separation processes and energy conversion. Yet lack of complete understanding at the single-conduit level limits development of new carbon nanofluidic structures and devices with desired transport properties for practical applications. Here, we show that the hydraulic resistance and slippage of single graphene nanochannels can be accurately determined using capillary flow and a novel hybrid nanochannel design without estimating the capillary pressure. Our results reveal that the slip length of graphene in the graphene nanochannels is around 16 nm, albeit with a large variation from 0 to 200 nm regardless of the channel height. We corroborate this finding with molecular dynamics simulation results, which indicate that this wide distribution of the slip length is due to the surface charge of graphene as well as the interaction between graphene and its silica substrate.

    更新日期:2018-01-01
  • A broadband achromatic metalens for focusing and imaging in the visible
    Nat. Nanotech. (IF 38.986) Pub Date : 2018-01-01
    Wei Ting Chen, Alexander Y. Zhu, Vyshakh Sanjeev, Mohammadreza Khorasaninejad, Zhujun Shi, Eric Lee, Federico Capasso

    A key goal of metalens research is to achieve wavefront shaping of light using optical elements with thicknesses on the order of the wavelength. Such miniaturization is expected to lead to compact, nanoscale optical devices with applications in cameras, lighting, displays and wearable optics. However, retaining functionality while reducing device size has proven particularly challenging. For example, so far there has been no demonstration of broadband achromatic metalenses covering the entire visible spectrum. Here, we show that by judicious design of nanofins on a surface, it is possible to simultaneously control the phase, group delay and group delay dispersion of light, thereby achieving a transmissive achromatic metalens with large bandwidth. We demonstrate diffraction-limited achromatic focusing and achromatic imaging from 470 to 670 nm. Our metalens comprises only a single layer of nanostructures whose thickness is on the order of the wavelength, and does not involve spatial multiplexing or cascading. While this initial design (numerical aperture of 0.2) has an efficiency of about 20% at 500 nm, we discuss ways in which our approach may be further optimized to meet the demand of future applications.

    更新日期:2018-01-01
  • A few-layer molecular film on polymer substrates to enhance the performance of organic devices
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Tomoyuki Yokota, Takashi Kajitani, Ren Shidachi, Takeyoshi Tokuhara, Martin Kaltenbrunner, Yoshiaki Shoji, Fumitaka Ishiwari, Tsuyoshi Sekitani, Takanori Fukushima, Takao Someya

    In organic electronics the functionalization of dielectric substrates with self-assembled monolayers is regarded as an effective surface modification strategy that may significantly improve the resulting device performance. However, this technique is not suitable for polymer substrates typically used in flexible electronics. Here, we report organic modifiers based on a paraffinic tripodal triptycene, which self-assembles into a completely oriented two-dimensional hexagonal triptycene array and one-dimensional layer stacking structure on polymer surfaces. Such few-layer films are analogous to conventional self-assembled monolayers on inorganic substrates in that they neutralize the polymer surface. Furthermore, the triptycene films significantly improve the crystallinity of an organic semiconductor and the overall performance of organic thin-film transistors, therefore enabling the fabrication of high-performance organic complementary circuits on polymer substrates with high oscillation speeds and low operation voltage.

    更新日期:2017-12-18
  • Steep-slope hysteresis-free negative capacitance MoS2 transistors
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Mengwei Si, Chun-Jung Su, Chunsheng Jiang, Nathan J. Conrad, Hong Zhou, Kerry D. Maize, Gang Qiu, Chien-Ting Wu, Ali Shakouri, Muhammad A. Alam, Peide D. Ye

    The so-called Boltzmann tyranny defines the fundamental thermionic limit of the subthreshold slope of a metal–oxide–semiconductor field-effect transistor (MOSFET) at 60 mV dec−1 at room temperature and therefore precludes lowering of the supply voltage and overall power consumption1,2. Adding a ferroelectric negative capacitor to the gate stack of a MOSFET may offer a promising solution to bypassing this fundamental barrier3. Meanwhile, two-dimensional semiconductors such as atomically thin transition-metal dichalcogenides, due to their low dielectric constant and ease of integration into a junctionless transistor topology, offer enhanced electrostatic control of the channel4,5,6,7,8,9,10,11,12. Here, we combine these two advantages and demonstrate a molybdenum disulfide (MoS2) two-dimensional steep-slope transistor with a ferroelectric hafnium zirconium oxide layer in the gate dielectric stack. This device exhibits excellent performance in both on and off states, with a maximum drain current of 510 μA μm−1 and a sub-thermionic subthreshold slope, and is essentially hysteresis-free. Negative differential resistance was observed at room temperature in the MoS2 negative-capacitance FETs as the result of negative capacitance due to the negative drain-induced barrier lowering. A high on-current-induced self-heating effect was also observed and studied.

    更新日期:2017-12-18
  • Ultrahard carbon film from epitaxial two-layer graphene
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Yang Gao, Tengfei Cao, Filippo Cellini, Claire Berger, Walter A. de Heer, Erio Tosatti, Elisa Riedo, Angelo Bongiorno

    Atomically thin graphene exhibits fascinating mechanical properties, although its hardness and transverse stiffness are inferior to those of diamond. So far, there has been no practical demonstration of the transformation of multilayer graphene into diamond-like ultrahard structures. Here we show that at room temperature and after nano-indentation, two-layer graphene on SiC(0001) exhibits a transverse stiffness and hardness comparable to diamond, is resistant to perforation with a diamond indenter and shows a reversible drop in electrical conductivity upon indentation. Density functional theory calculations suggest that, upon compression, the two-layer graphene film transforms into a diamond-like film, producing both elastic deformations and sp2 to sp3 chemical changes. Experiments and calculations show that this reversible phase change is not observed for a single buffer layer on SiC or graphene films thicker than three to five layers. Indeed, calculations show that whereas in two-layer graphene layer-stacking configuration controls the conformation of the diamond-like film, in a multilayer film it hinders the phase transformation.

    更新日期:2017-12-18
  • Peltier cooling in molecular junctions
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Longji Cui, Ruijiao Miao, Kun Wang, Dakotah Thompson, Linda Angela Zotti, Juan Carlos Cuevas, Edgar Meyhofer, Pramod Reddy

    The study of thermoelectricity in molecular junctions is of fundamental interest for the development of various technologies including cooling (refrigeration) and heat-to-electricity conversion1,2,3,4. Recent experimental progress in probing the thermopower (Seebeck effect) of molecular junctions5,6,7,8,9 has enabled studies of the relationship between thermoelectricity and molecular structure10,11. However, observations of Peltier cooling in molecular junctions—a critical step for establishing molecular-based refrigeration—have remained inaccessible. Here, we report direct experimental observations of Peltier cooling in molecular junctions. By integrating conducting-probe atomic force microscopy12,13 with custom-fabricated picowatt-resolution calorimetric microdevices, we created an experimental platform that enables the unified characterization of electrical, thermoelectric and energy dissipation characteristics of molecular junctions. Using this platform, we studied gold junctions with prototypical molecules (Au–biphenyl-4,4′-dithiol–Au, Au–terphenyl-4,4′′-dithiol–Au and Au–4,4′-bipyridine–Au) and revealed the relationship between heating or cooling and charge transmission characteristics. Our experimental conclusions are supported by self-energy-corrected density functional theory calculations. We expect these advances to stimulate studies of both thermal and thermoelectric transport in molecular junctions where the possibility of extraordinarily efficient energy conversion has been theoretically predicted2,3,4,14.

    更新日期:2017-12-18
  • Peltier cooling at molecular scale
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Keehoon Kang, Takhee Lee

    Peltier cooling at molecular scale Peltier cooling at molecular scale, Published online: 18 December 2017; doi:10.1038/s41565-017-0036-4 Under specific conditions, molecular monolayers dissipate power more than they heat up at one end of a molecular junction, validating theoretical predictions of Peltier cooling.

    更新日期:2017-12-18
  • Excitonic pathway to photoinduced magnetism in colloidal nanocrystals with nonmagnetic dopants
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Valerio Pinchetti, Qiumei Di, Monica Lorenzon, Andrea Camellini, Mauro Fasoli, Margherita Zavelani-Rossi, Francesco Meinardi, Jiatao Zhang, Scott A. Crooker, Sergio Brovelli

    Electronic doping of colloidal semiconductor nanostructures holds promise for future device concepts in optoelectronic and spin-based technologies. Ag+ is an emerging electronic dopant in iii–v and ii–vi nanostructures, introducing intragap electronic states optically coupled to the host conduction band. With its full 4d shell Ag+ is nonmagnetic, and the dopant-related luminescence is ascribed to decay of the conduction-band electron following transfer of the photoexcited hole to Ag+. This optical activation process and the associated modification of the electronic configuration of Ag+ remain unclear. Here, we trace a comprehensive picture of the excitonic process in Ag-doped CdSe nanocrystals and demonstrate that, in contrast to expectations, capture of the photohole leads to conversion of Ag+ to paramagnetic Ag2+. The process of exciton recombination is thus inextricably tied to photoinduced magnetism. Accordingly, we observe strong optically activated magnetism and diluted magnetic semiconductor behaviour, demonstrating that optically switchable magnetic nanomaterials can be obtained by exploiting excitonic processes involving nonmagnetic impurities.

    更新日期:2017-12-18
  • Negative capacitance gives a positive boost
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Adrian M. Ionescu

    Negative capacitance gives a positive boost Negative capacitance gives a positive boost, Published online: 18 December 2017; doi:10.1038/s41565-017-0046-2 Negative capacitance effect in a ferroelectric-based gate stack provides an effective solution for hysteresis-free steep-slope  operation in a MoS2 field-effect transistor.

    更新日期:2017-12-18
  • A quantum-dot spin qubit with coherence limited by charge noise and fidelity higher than 99.9%
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-18
    Jun Yoneda, Kenta Takeda, Tomohiro Otsuka, Takashi Nakajima, Matthieu R. Delbecq, Giles Allison, Takumu Honda, Tetsuo Kodera, Shunri Oda, Yusuke Hoshi, Noritaka Usami, Kohei M. Itoh, Seigo Tarucha

    The isolation of qubits from noise sources, such as surrounding nuclear spins and spin–electric susceptibility1,2,3,4, has enabled extensions of quantum coherence times in recent pivotal advances towards the concrete implementation of spin-based quantum computation. In fact, the possibility of achieving enhanced quantum coherence has been substantially doubted for nanostructures due to the characteristic high degree of background charge fluctuations5,6,7. Still, a sizeable spin–electric coupling will be needed in realistic multiple-qubit systems to address single-spin and spin–spin manipulations8,9,10. Here, we realize a single-electron spin qubit with an isotopically enriched phase coherence time (20 μs)11,12 and fast electrical control speed (up to 30 MHz) mediated by extrinsic spin–electric coupling. Using rapid spin rotations, we reveal that the free-evolution dephasing is caused by charge noise—rather than conventional magnetic noise—as highlighted by a 1/f spectrum extended over seven decades of frequency. The qubit exhibits superior performance with single-qubit gate fidelities exceeding 99.9% on average, offering a promising route to large-scale spin-qubit systems with fault-tolerant controllability.

    更新日期:2017-12-18
  • Bridging the gap with hot electrons
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-11
    Jason Valentine

    Bridging the gap with hot electrons Bridging the gap with hot electrons, Published online: 11 December 2017; doi:10.1038/s41565-017-0037-3 Tunnel junctions fabricated over a large area provide a platform for efficient generation and utilization of hot carriers.

    更新日期:2017-12-11
  • Nanoparticle orientation to control RNA loading and ligand display on extracellular vesicles for cancer regression
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-11
    Fengmei Pi, Daniel W. Binzel, Tae Jin Lee, Zhefeng Li, Meiyan Sun, Piotr Rychahou, Hui Li, Farzin Haque, Shaoying Wang, Carlo M. Croce, Bin Guo, B. Mark Evers, Peixuan Guo

    Nanotechnology offers many benefits, and here we report an advantage of applying RNA nanotechnology for directional control. The orientation of arrow-shaped RNA was altered to control ligand display on extracellular vesicle membranes for specific cell targeting, or to regulate intracellular trafficking of small interfering RNA (siRNA) or microRNA (miRNA). Placing membrane-anchoring cholesterol at the tail of the arrow results in display of RNA aptamer or folate on the outer surface of the extracellular vesicle. In contrast, placing the cholesterol at the arrowhead results in partial loading of RNA nanoparticles into the extracellular vesicles. Taking advantage of the RNA ligand for specific targeting and extracellular vesicles for efficient membrane fusion, the resulting ligand-displaying extracellular vesicles were capable of specific delivery of siRNA to cells, and efficiently blocked tumour growth in three cancer models. Extracellular vesicles displaying an aptamer that binds to prostate-specific membrane antigen, and loaded with survivin siRNA, inhibited prostate cancer xenograft. The same extracellular vesicle instead displaying epidermal growth-factor receptor aptamer inhibited orthotopic breast cancer models. Likewise, survivin siRNA-loaded and folate-displaying extracellular vesicles inhibited patient-derived colorectal cancer xenograft.

    更新日期:2017-12-11
  • Direct-current triboelectricity generation by a sliding Schottky nanocontact on MoS2 multilayers
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-11
    Jun Liu, Ankur Goswami, Keren Jiang, Faheem Khan, Seokbeom Kim, Ryan McGee, Zhi Li, Zhiyu Hu, Jungchul Lee, Thomas Thundat

    The direct conversion of mechanical energy into electricity by nanomaterial-based devices offers potential for green energy harvesting1,2,3. A conventional triboelectric nanogenerator converts frictional energy into electricity by producing alternating current (a.c.) triboelectricity. However, this approach is limited by low current density and the need for rectification2. Here, we show that continuous direct-current (d.c.) with a maximum density of 106 A m−2 can be directly generated by a sliding Schottky nanocontact without the application of an external voltage. We demonstrate this by sliding a conductive-atomic force microscope tip on a thin film of molybdenum disulfide (MoS2). Finite element simulation reveals that the anomalously high current density can be attributed to the non-equilibrium carrier transport phenomenon enhanced by the strong local electrical field (105−106 V m−2) at the conductive nanoscale tip4. We hypothesize that the charge transport may be induced by electronic excitation under friction, and the nanoscale current−voltage spectra analysis indicates that the rectifying Schottky barrier at the tip–sample interface plays a critical role in efficient d.c. energy harvesting. This concept is scalable when combined with microfabricated or contact surface modified electrodes, which makes it promising for efficient d.c. triboelectricity generation.

    更新日期:2017-12-11
  • Reactive tunnel junctions in electrically driven plasmonic nanorod metamaterials
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-11
    Pan Wang, Alexey V. Krasavin, Mazhar E. Nasir, Wayne Dickson, Anatoly V. Zayats

    Non-equilibrium hot carriers formed near the interfaces of semiconductors or metals play a crucial role in chemical catalysis and optoelectronic processes. In addition to optical illumination, an efficient way to generate hot carriers is by excitation with tunnelling electrons. Here, we show that the generation of hot electrons makes the nanoscale tunnel junctions highly reactive and facilitates strongly confined chemical reactions that can, in turn, modulate the tunnelling processes. We designed a device containing an array of electrically driven plasmonic nanorods with up to 1011 tunnel junctions per square centimetre, which demonstrates hot-electron activation of oxidation and reduction reactions in the junctions, induced by the presence of O2 and H2 molecules, respectively. The kinetics of the reactions can be monitored in situ following the radiative decay of tunnelling-induced surface plasmons. This electrically driven plasmonic nanorod metamaterial platform can be useful for the development of nanoscale chemical and optoelectronic devices based on electron tunnelling.

    更新日期:2017-12-11
  • The shortfall of risk assessment for decision-making
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    Rune Hjorth

    The shortfall of risk assessment for decision-making The shortfall of risk assessment for decision-making, Published online: 06 December 2017; doi:10.1038/nnano.2017.232 The shortfall of risk assessment for decision-making

    更新日期:2017-12-06
  • On phonons and water flow enhancement in carbon nanotubes
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    Eduardo R. Cruz-Chú, Ermioni Papadopoulou, Jens H. Walther, Aleksandar Popadić, Gengyun Li, Matej Praprotnik, Petros Koumoutsakos

    On phonons and water flow enhancement in carbon nanotubes On phonons and water flow enhancement in carbon nanotubes, Published online: 06 December 2017; doi:10.1038/nnano.2017.234 On phonons and water flow enhancement in carbon nanotubes

    更新日期:2017-12-06
  • DNA nanotechnology: DNA robots that sort cargoes
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    Wenjie Sun

    DNA nanotechnology: DNA robots that sort cargoes DNA nanotechnology: DNA robots that sort cargoes, Published online: 06 December 2017; doi:10.1038/nnano.2017.236 DNA nanotechnology: DNA robots that sort cargoes

    更新日期:2017-12-06
  • Our choice from the recent literature
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06

    Our choice from the recent literature Our choice from the recent literature, Published online: 06 December 2017; doi:10.1038/nnano.2017.238 Our choice from the recent literature

    更新日期:2017-12-06
  • Water splitting: Vacancy-filling with P
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    Adam Weingarten

    Water splitting: Vacancy-filling with P Water splitting: Vacancy-filling with P, Published online: 06 December 2017; doi:10.1038/nnano.2017.241 Water splitting: Vacancy-filling with P

    更新日期:2017-12-06
  • Spin caloritronics: Spin Nernst effect
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    Giacomo Prando

    Spin caloritronics: Spin Nernst effect Spin caloritronics: Spin Nernst effect, Published online: 06 December 2017; doi:10.1038/nnano.2017.239 Spin caloritronics: Spin Nernst effect

    更新日期:2017-12-06
  • How to build a nanotech company
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    James Vicary

    How to build a nanotech company How to build a nanotech company, Published online: 06 December 2017; doi:10.1038/nnano.2017.231 What do you need to consider when launching a scientific start-up? James Vicary highlights what in his views are the three main issues.

    更新日期:2017-12-06
  • Reproducibility, sharing and progress in nanomaterial databases
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-06
    Alexander Tropsha, Karmann C. Mills, Anthony J. Hickey

    Reproducibility, sharing and progress in nanomaterial databases Reproducibility, sharing and progress in nanomaterial databases, Published online: 06 December 2017; doi:10.1038/nnano.2017.233 Publicly accessible databases are core resources for data-rich research, consolidating field-specific knowledge and highlighting best practices and challenges. Further effective growth of nanomaterial databases requires the concerted efforts of database stewards, researchers, funding agencies and publishers.

    更新日期:2017-12-06
  • Synthetically lethal nanoparticles for treatment of endometrial cancer
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-04
    Kareem Ebeid, Xiangbing Meng, Kristina W. Thiel, Anh-Vu Do, Sean M. Geary, Angie S. Morris, Erica L. Pham, Amaraporn Wongrakpanich, Yashpal S. Chhonker, Daryl J. Murry, Kimberly K. Leslie, Aliasger K. Salem

    Uterine serous carcinoma, one of the most aggressive types of endometrial cancer, is characterized by poor outcomes and mutations in the tumour suppressor p53. Our objective was to engender synthetic lethality to paclitaxel (PTX), the frontline treatment for endometrial cancer, in tumours with mutant p53 and enhance the therapeutic efficacy using polymeric nanoparticles (NPs). First, we identified the optimal NP formulation through comprehensive analyses of release profiles and cellular-uptake and cell viability studies. Not only were PTX-loaded NPs superior to PTX in solution, but the combination of PTX-loaded NPs with the antiangiogenic molecular inhibitor BIBF 1120 (BIBF) promoted synthetic lethality specifically in cells with the loss-of-function (LOF) p53 mutation. In a xenograft model of endometrial cancer, this combinatorial therapy resulted in a marked inhibition of tumour progression and extended survival. Together, our data provide compelling evidence for future studies of BIBF- and PTX-loaded NPs as a therapeutic opportunity for LOF p53 cancers.

    更新日期:2017-12-05
  • Humidity-controlled rectification switching in ruthenium-complex molecular junctions
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-04
    Huseyin Atesci, Veerabhadrarao Kaliginedi, Jose A. Celis Gil, Hiroaki Ozawa, Joseph M. Thijssen, Peter Broekmann, Masa-aki Haga, Sense Jan van der Molen

    Although molecular rectifiers were proposed over four decades ago1,2, until recently reported rectification ratios (RR) were rather moderate2,3,4,5,6,7,8,9,10,11 (RR ~ 101). This ceiling was convincingly broken using a eutectic GaIn top contact12 to probe molecular monolayers of coupled ferrocene groups (RR ~ 105), as well as using scanning tunnelling microscopy-break junctions13,14,15,16 and mechanically controlled break junctions17 to probe single molecules (RR ~ 102–103). Here, we demonstrate a device based on a molecular monolayer in which the RR can be switched by more than three orders of magnitude (between RR ~ 100 and RR ≥ 103) in response to humidity. As the relative humidity is toggled between 5% and 60%, the current–voltage (I–V) characteristics of a monolayer of di-nuclear Ru-complex molecules reversibly change from symmetric to strongly asymmetric (diode-like). Key to this behaviour is the presence of two localized molecular orbitals in series, which are nearly degenerate in dry circumstances but become misaligned under high humidity conditions, due to the displacement of counter ions (PF6–). This asymmetric gating of the two relevant localized molecular orbital levels results in humidity-controlled diode-like behaviour.

    更新日期:2017-12-05
  • A synthetic lethal bullet
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-04
    Christian Rolfo, Elisa Giovannetti

    A synthetic lethal bullet A synthetic lethal bullet, Published online: 04 December 2017; doi:10.1038/s41565-017-0038-2 Nanoparticles loaded with paclitaxel and nintedanib induce synthetic lethality in endometrial cancer cells.

    更新日期:2017-12-05
  • Bacterial resistance to silver nanoparticles and how to overcome it
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-04
    Aleš Panáček, Libor Kvítek, Monika Smékalová, Renata Večeřová, Milan Kolář, Magdalena Röderová, Filip Dyčka, Marek Šebela, Robert Prucek, Ondřej Tomanec, Radek Zbořil

    Silver nanoparticles have already been successfully applied in various biomedical and antimicrobial technologies and products used in everyday life. Although bacterial resistance to antibiotics has been extensively discussed in the literature, the possible development of resistance to silver nanoparticles has not been fully explored. We report that the Gram-negative bacteria Escherichia coli 013, Pseudomonas aeruginosa CCM 3955 and E. coli CCM 3954 can develop resistance to silver nanoparticles after repeated exposure. The resistance stems from the production of the adhesive flagellum protein flagellin, which triggers the aggregation of the nanoparticles. This resistance evolves without any genetic changes; only phenotypic change is needed to reduce the nanoparticles’ colloidal stability and thus eliminate their antibacterial activity. The resistance mechanism cannot be overcome by additional stabilization of silver nanoparticles using surfactants or polymers. It is, however, strongly suppressed by inhibiting flagellin production with pomegranate rind extract.

    更新日期:2017-12-05
  • Thermoelectric spin voltage in graphene
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-12-04
    Juan F. Sierra, Ingmar Neumann, Jo Cuppens, Bart Raes, Marius V. Costache, Sergio O. Valenzuela

    In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents1,2. Amongst the most intriguing phenomena is the spin Seebeck effect3,4,5, in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect6,7,8. Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport9,10,11, energy-dependent carrier mobility and unique density of states12,13. Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current14,15,16,17. These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias.

    更新日期:2017-12-05
  • A graphene Zener–Klein transistor cooled by a hyperbolic substrate
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-27
    Wei Yang, Simon Berthou, Xiaobo Lu, Quentin Wilmart, Anne Denis, Michael Rosticher, Takashi Taniguchi, Kenji Watanabe, Gwendal Fève, Jean-Marc Berroir, Guangyu Zhang, Christophe Voisin, Emmanuel Baudin, Bernard Plaçais

    The engineering of cooling mechanisms is a bottleneck in nanoelectronics. Thermal exchanges in diffusive graphene are mostly driven by defect-assisted acoustic phonon scattering, but the case of high-mobility graphene on hexagonal boron nitride (hBN) is radically different, with a prominent contribution of remote phonons from the substrate. Bilayer graphene on a hBN transistor with a local gate is driven in a regime where almost perfect current saturation is achieved by compensation of the decrease in the carrier density and Zener–Klein tunnelling (ZKT) at high bias. Using noise thermometry, we show that the ZKT triggers a new cooling pathway due to the emission of hyperbolic phonon polaritons in hBN by out-of-equilibrium electron–hole pairs beyond the super-Planckian regime. The combination of ZKT transport and hyperbolic phonon polariton cooling renders graphene on BN transistors a valuable nanotechnology for power devices and RF electronics.

    更新日期:2017-11-28
  • Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-27
    Sheng Wang, Diego Scarabelli, Lingjie Du, Yuliya Y. Kuznetsova, Loren N. Pfeiffer, Ken W. West, Geoff C. Gardner, Michael J. Manfra, Vittorio Pellegrini, Shalom J. Wind, Aron Pinczuk

    Charge carriers in graphene behave like massless Dirac fermions (MDFs) with linear energy-momentum dispersion1, 2, providing a condensed-matter platform for studying quasiparticles with relativistic-like features. Artificial graphene (AG)—a structure with an artificial honeycomb lattice—exhibits novel phenomena due to the tunable interplay between topology and quasiparticle interactions3,4,5,6. So far, the emergence of a Dirac band structure supporting MDFs has been observed in AG using molecular5, atomic6, 7 and photonic systems8,9,10, including those with semiconductor microcavities11. Here, we report the realization of an AG that has a band structure with vanishing density of states consistent with the presence of MDFs. This observation is enabled by a very small lattice constant (a = 50 nm) of the nanofabricated AG patterns superimposed on a two-dimensional electron gas hosted by a high-quality GaAs quantum well. Resonant inelastic light-scattering spectra reveal low-lying transitions that are not present in the unpatterned GaAs quantum well. These excitations reveal the energy dependence of the joint density of states for AG band transitions. Fermi level tuning through the Dirac point results in a collapse of the density of states at low transition energy, suggesting the emergence of the MDF linear dispersion in the AG.

    更新日期:2017-11-28
  • Out-of-plane heat transfer in van der Waals stacks through electron–hyperbolic phonon coupling
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-27
    Klaas-Jan Tielrooij, Niels C. H. Hesp, Alessandro Principi, Mark B. Lundeberg, Eva A. A. Pogna, Luca Banszerus, Zoltán Mics, Mathieu Massicotte, Peter Schmidt, Diana Davydovskaya, David G. Purdie, Ilya Goykhman, Giancarlo Soavi, Antonio Lombardo, Kenji Watanabe, Takashi Taniguchi, Mischa Bonn, Dmitry Turchinovich, Christoph Stampfer, Andrea C. Ferrari, Giulio Cerullo, Marco Polini, Frank H. L. Koppens

    Van der Waals heterostructures have emerged as promising building blocks that offer access to new physics, novel device functionalities and superior electrical and optoelectronic properties1,2,3,4,5,6,7. Applications such as thermal management, photodetection, light emission, data communication, high-speed electronics and light harvesting8,9,10,11,12,13,14,15,16 require a thorough understanding of (nanoscale) heat flow. Here, using time-resolved photocurrent measurements, we identify an efficient out-of-plane energy transfer channel, where charge carriers in graphene couple to hyperbolic phonon polaritons17,18,19 in the encapsulating layered material. This hyperbolic cooling is particularly efficient, giving picosecond cooling times for hexagonal BN, where the high-momentum hyperbolic phonon polaritons enable efficient near-field energy transfer. We study this heat transfer mechanism using distinct control knobs to vary carrier density and lattice temperature, and find excellent agreement with theory without any adjustable parameters. These insights may lead to the ability to control heat flow in van der Waals heterostructures.

    更新日期:2017-11-28
  • A graphene Zener–Klein transistor cooled by a hyperbolic substrate
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-27
    Wei Yang, Simon Berthou, Xiaobo Lu, Quentin Wilmart, Anne Denis, Michael Rosticher, Takashi Taniguchi, Kenji Watanabe, Gwendal Fève, Jean-Marc Berroir, Guangyu Zhang, Christophe Voisin, Emmanuel Baudin, Bernard Plaçais

    The engineering of cooling mechanisms is a bottleneck in nanoelectronics. Thermal exchanges in diffusive graphene are mostly driven by defect-assisted acoustic phonon scattering, but the case of high-mobility graphene on hexagonal boron nitride (hBN) is radically different, with a prominent contribution of remote phonons from the substrate. Bilayer graphene on a hBN transistor with a local gate is driven in a regime where almost perfect current saturation is achieved by compensation of the decrease in the carrier density and Zener–Klein tunnelling (ZKT) at high bias. Using noise thermometry, we show that the ZKT triggers a new cooling pathway due to the emission of hyperbolic phonon polaritons in hBN by out-of-equilibrium electron–hole pairs beyond the super-Planckian regime. The combination of ZKT transport and hyperbolic phonon polariton cooling renders graphene on BN transistors a valuable nanotechnology for power devices and RF electronics.

    更新日期:2017-11-28
  • Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-27
    Sheng Wang, Diego Scarabelli, Lingjie Du, Yuliya Y. Kuznetsova, Loren N. Pfeiffer, Ken W. West, Geoff C. Gardner, Michael J. Manfra, Vittorio Pellegrini, Shalom J. Wind, Aron Pinczuk

    Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells, Published online: 27 November 2017; doi:10.1038/s41565-017-0006-x Advanced nanoengineering of small-period AG lattices enables the observation of a vanishing density of states that suggests the presence of massless Dirac fermions.

    更新日期:2017-11-28
  • Out-of-plane heat transfer in van der Waals stacks through electron–hyperbolic phonon coupling
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-27
    Klaas-Jan Tielrooij, Niels C. H. Hesp, Alessandro Principi, Mark B. Lundeberg, Eva A. A. Pogna, Luca Banszerus, Zoltán Mics, Mathieu Massicotte, Peter Schmidt, Diana Davydovskaya, David G. Purdie, Ilya Goykhman, Giancarlo Soavi, Antonio Lombardo, Kenji Watanabe, Takashi Taniguchi, Mischa Bonn, Dmitry Turchinovich, Christoph Stampfer, Andrea C. Ferrari, Giulio Cerullo, Marco Polini, Frank H. L. Koppens

    Van der Waals heterostructures have emerged as promising building blocks that offer access to new physics, novel device functionalities and superior electrical and optoelectronic properties1,2,3,4,5,6,7. Applications such as thermal management, photodetection, light emission, data communication, high-speed electronics and light harvesting8,9,10,11,12,13,14,15,16 require a thorough understanding of (nanoscale) heat flow. Here, using time-resolved photocurrent measurements, we identify an efficient out-of-plane energy transfer channel, where charge carriers in graphene couple to hyperbolic phonon polaritons17,18,19 in the encapsulating layered material. This hyperbolic cooling is particularly efficient, giving picosecond cooling times for hexagonal BN, where the high-momentum hyperbolic phonon polaritons enable efficient near-field energy transfer. We study this heat transfer mechanism using distinct control knobs to vary carrier density and lattice temperature, and find excellent agreement with theory without any adjustable parameters. These insights may lead to the ability to control heat flow in van der Waals heterostructures.

    更新日期:2017-11-28
  • Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-20
    Kyoung-Duck Park, Tao Jiang, Genevieve Clark, Xiaodong Xu, Markus B. Raschke

    Excitons, Coulomb-bound electron–hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (XD) show anti-parallel spin configuration with generally forbidden radiative emission. Because of their long lifetimes, these dark excitons are appealing candidates for quantum computing and optoelectronics. However, optical read-out and control of XD states has remained challenging due to their decoupling from light. Here, we present a tip-enhanced nano-optical approach to induce, switch and programmably modulate the XD emission at room temperature. Using a monolayer transition metal dichalcogenide (TMD) WSe2 on a gold substrate, we demonstrate ~6 × 105-fold enhancement in dark exciton photoluminescence quantum yield achieved through coupling of the antenna-tip to the dark exciton out-of-plane optical dipole moment, with a large Purcell factor of ≥2 × 103 of the tip–sample nano-cavity. Our approach provides a facile way to harness excitonic properties in low-dimensional semiconductors offering new strategies for quantum optoelectronics.

    更新日期:2017-11-21
  • Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-20
    Jack C. Gartside, Daan M. Arroo, David M. Burn, Victoria L. Bemmer, Andy Moskalenko, Lesley F. Cohen, Will R. Branford

    Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing—a scanning probe technique—provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy ‘monopole-chain’ states that exhibit negative effective temperatures.

    更新日期:2017-11-21
  • Write it as you like it
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-20
    Cristiano Nisoli

    Write it as you like it Write it as you like it, Published online: 20 November 2017; doi:10.1038/s41565-017-0021-y The microstate of geometrically frustrated two-dimensional arrays of strongly interacting nanomagnets is controlled by means of topological defect-driven magnetic writing, to the extent that elusive configurations such as the ground state and negative-temperature states are realized.

    更新日期:2017-11-21
  • Radiative control of dark excitons at room temperature by nano-optical antenna-tip Purcell effect
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-20
    Kyoung-Duck Park, Tao Jiang, Genevieve Clark, Xiaodong Xu, Markus B. Raschke

    Excitons, Coulomb-bound electron–hole pairs, are elementary photo-excitations in semiconductors that can couple to light through radiative relaxation. In contrast, dark excitons (XD) show anti-parallel spin configuration with generally forbidden radiative emission. Because of their long lifetimes, these dark excitons are appealing candidates for quantum computing and optoelectronics. However, optical read-out and control of XD states has remained challenging due to their decoupling from light. Here, we present a tip-enhanced nano-optical approach to induce, switch and programmably modulate the XD emission at room temperature. Using a monolayer transition metal dichalcogenide (TMD) WSe2 on a gold substrate, we demonstrate ~6 × 105-fold enhancement in dark exciton photoluminescence quantum yield achieved through coupling of the antenna-tip to the dark exciton out-of-plane optical dipole moment, with a large Purcell factor of ≥2 × 103 of the tip–sample nano-cavity. Our approach provides a facile way to harness excitonic properties in low-dimensional semiconductors offering new strategies for quantum optoelectronics.

    更新日期:2017-11-21
  • Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-20
    Jack C. Gartside, Daan M. Arroo, David M. Burn, Victoria L. Bemmer, Andy Moskalenko, Lesley F. Cohen, Will R. Branford

    Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing—a scanning probe technique—provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy ‘monopole-chain’ states that exhibit negative effective temperatures.

    更新日期:2017-11-21
  • Write it as you like it
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-20
    Cristiano Nisoli

    Write it as you like it Write it as you like it, Published online: 20 November 2017; doi:10.1038/s41565-017-0021-y The microstate of geometrically frustrated two-dimensional arrays of strongly interacting nanomagnets is controlled by means of topological defect-driven magnetic writing, to the extent that elusive configurations such as the ground state and negative-temperature states are realized.

    更新日期:2017-11-21
  • Genetic programs can be compressed and autonomously decompressed in live cells
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-13
    Nicolas Lapique, Yaakov Benenson

    Fundamental computer science concepts have inspired novel information-processing molecular systems in test tubes1,2,3,4,5,6,7,8,9,10,11,12,13 and genetically encoded circuits in live cells14,15,16,17,18,19,20,21. Recent research has shown that digital information storage in DNA, implemented using deep sequencing and conventional software, can approach the maximum Shannon information capacity22 of two bits per nucleotide23. In nature, DNA is used to store genetic programs, but the information content of the encoding rarely approaches this maximum24. We hypothesize that the biological function of a genetic program can be preserved while reducing the length of its DNA encoding and increasing the information content per nucleotide. Here we support this hypothesis by describing an experimental procedure for compressing a genetic program and its subsequent autonomous decompression and execution in human cells. As a test-bed we choose an RNAi cell classifier circuit25 that comprises redundant DNA sequences and is therefore amenable for compression, as are many other complex gene circuits15,18,26,27,28. In one example, we implement a compressed encoding of a ten-gene four-input AND gate circuit using only four genetic constructs. The compression principles applied to gene circuits can enable fitting complex genetic programs into DNA delivery vehicles with limited cargo capacity, and storing compressed and biologically inert programs in vivo for on-demand activation.

    更新日期:2017-11-13
  • Genetic programs can be compressed and autonomously decompressed in live cells
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-13
    Nicolas Lapique, Yaakov Benenson

    Fundamental computer science concepts have inspired novel information-processing molecular systems in test tubes1,2,3,4,5,6,7,8,9,10,11,12,13 and genetically encoded circuits in live cells14,15,16,17,18,19,20,21. Recent research has shown that digital information storage in DNA, implemented using deep sequencing and conventional software, can approach the maximum Shannon information capacity22 of two bits per nucleotide23. In nature, DNA is used to store genetic programs, but the information content of the encoding rarely approaches this maximum24. We hypothesize that the biological function of a genetic program can be preserved while reducing the length of its DNA encoding and increasing the information content per nucleotide. Here we support this hypothesis by describing an experimental procedure for compressing a genetic program and its subsequent autonomous decompression and execution in human cells. As a test-bed we choose an RNAi cell classifier circuit25 that comprises redundant DNA sequences and is therefore amenable for compression, as are many other complex gene circuits15,18,26,27,28. In one example, we implement a compressed encoding of a ten-gene four-input AND gate circuit using only four genetic constructs. The compression principles applied to gene circuits can enable fitting complex genetic programs into DNA delivery vehicles with limited cargo capacity, and storing compressed and biologically inert programs in vivo for on-demand activation.

    更新日期:2017-11-13
  • Drug delivery: Lean by design
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-07
    Chiara Pastore

    Drug delivery: Lean by design Drug delivery: Lean by design, Published online: 07 November 2017; doi:10.1038/nnano.2017.225

    更新日期:2017-11-07
  • Scanning tunnelling microscopy: Orbital ordering mapped
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-07
    Giacomo Prando

    Scanning tunnelling microscopy: Orbital ordering mapped Scanning tunnelling microscopy: Orbital ordering mapped, Published online: 07 November 2017; doi:10.1038/nnano.2017.227

    更新日期:2017-11-07
  • High-performance semiconductor quantum-dot single-photon sources
    Nat. Nanotech. (IF 38.986) Pub Date : 2017-11-01
    Pascale Senellart, Glenn Solomon, Andrew White

    Single photons are a fundamental element of most quantum optical technologies. The ideal single-photon source is an on-demand, deterministic, single-photon source delivering light pulses in a well-defined polarization and spatiotemporal mode, and containing exactly one photon. In addition, for many applications, there is a quantum advantage if the single photons are indistinguishable in all their degrees of freedom. Single-photon sources based on parametric down-conversion are currently used, and while excellent in many ways, scaling to large quantum optical systems remains challenging. In 2000, semiconductor quantum dots were shown to emit single photons, opening a path towards integrated single-photon sources. Here, we review the progress achieved in the past few years, and discuss remaining challenges. The latest quantum dot-based single-photon sources are edging closer to the ideal single-photon source, and have opened new possibilities for quantum technologies.

    更新日期:2017-11-07
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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