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  • A missing step is a key step
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-17
    Fan Zhang, Wei Pan

    A missing step is a key stepA missing step is a key step, Published online: 17 September 2018; doi:10.1038/s41563-018-0179-1Physicists are searching for superconducting materials that can host Majoranas. New evidence for these elusive particles is provided by missing Shapiro steps in a Josephson effect mediated by an accidental Dirac semimetal.

    更新日期:2018-09-18
  • The mechanism of the ultrafast crystal growth of pure metals from their melts
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-17
    Gang Sun, Jenny Xu, Peter Harrowell

    Pure metals can have ultrafast growth rates from their melts, such as a crystal of pure nickel that grows at a rate reaching 70 m s−1. These extraordinary growth rates suggest that metallic crystals might provide the next generation of phase-change materials. The huge crystal growth rates of metals are the consequence of kinetics without activated control, in sharp contrast to the prediction of the ‘classic’ theory of crystal growth. While the existence of barrierless growth kinetics is now well established in atomic melts, the physical explanation for the absence of an activation barrier to ordering remains unclear. It is something of a paradox that diffusion in the liquid metal is governed by thermal activation while the movement of the same atoms organizing into a crystal is not. Here we use computer simulations of crystallization in pure metals to explicitly resolve the origin of the barrierless growth kinetics.

    更新日期:2018-09-18
  • 4π-periodic Andreev bound states in a Dirac semimetal
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-17
    Chuan Li, Jorrit C. de Boer, Bob de Ronde, Shyama V. Ramankutty, Erik van Heumen, Yingkai Huang, Anne de Visser, Alexander A. Golubov, Mark S. Golden, Alexander Brinkman

    Although signatures of superconductivity in Dirac semimetals have been reported, for instance by applying pressure or using point contacts, our understanding of the topological aspects of Dirac semimetal superconductivity is still developing. Here, we utilize nanoscale phase-sensitive junction technology to induce superconductivity in the Dirac semimetal Bi1−xSbx. Our radiofrequency irradiation experiments then reveal a significant contribution of 4π-periodic Andreev bound states to the supercurrent in Nb–Bi0.97Sb0.03–Nb Josephson junctions. The conditions for a substantial 4π contribution to the supercurrent are favourable because of the Dirac cone’s very broad transmission resonances and a measurement frequency faster than the quasiparticle poisoning rate. In addition, we show that a magnetic field applied in the plane of the junction allows tuning of the Josephson junctions from 0 to π regimes. Our results open the technologically appealing avenue of employing the topological bulk properties of Dirac semimetals for topological superconductivity research and topological quantum computer development.

    更新日期:2018-09-18
  • Fluid-enhanced surface diffusion controls intraparticle phase transformations
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-17
    Yiyang Li, Hungru Chen, Kipil Lim, Haitao D. Deng, Jongwoo Lim, Dimitrios Fraggedakis, Peter M. Attia, Sang Chul Lee, Norman Jin, Jože Moškon, Zixuan Guan, William E. Gent, Jihyun Hong, Young-Sang Yu, Miran Gaberšček, M. Saiful Islam, Martin Z. Bazant, William C. Chueh

    Phase transformations driven by compositional change require mass flux across a phase boundary. In some anisotropic solids, however, the phase boundary moves along a non-conductive crystallographic direction. One such material is LiXFePO4, an electrode for lithium-ion batteries. With poor bulk ionic transport along the direction of phase separation, it is unclear how lithium migrates during phase transformations. Here, we show that lithium migrates along the solid/liquid interface without leaving the particle, whereby charge carriers do not cross the double layer. X-ray diffraction and microscopy experiments as well as ab initio molecular dynamics simulations show that organic solvent and water molecules promote this surface ion diffusion, effectively rendering LiXFePO4 a three-dimensional lithium-ion conductor. Phase-field simulations capture the effects of surface diffusion on phase transformation. Lowering surface diffusivity is crucial towards supressing phase separation. This work establishes fluid-enhanced surface diffusion as a key dial for tuning phase transformation in anisotropic solids.

    更新日期:2018-09-18
  • Decoupling the role of stress and corrosion in the intergranular cracking of noble-metal alloys
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-10
    N. Badwe, X. Chen, D. K. Schreiber, M. J. Olszta, N. R. Overman, E. K. Karasz, A. Y. Tse, S. M. Bruemmer, K. Sieradzki

    Intergranular stress-corrosion cracking (IGSCC) is a form of environmentally induced crack propagation causing premature failure of elemental metals and alloys. It is believed to require the simultaneous presence of tensile stress and corrosion; however, the exact nature of this synergy has eluded experimental identification. For noble metal alloys such as Ag–Au, IGSCC is a consequence of dealloying corrosion, forming a nanoporous gold layer that is believed to have the ability to transmit cracks into grain boundaries in un-dealloyed parent phase via a pure mechanical process. Here using atomic-scale techniques and statistical characterizations for this alloy system, we show that the separate roles of stress and anodic dissolution can be decoupled and that the apparent synergy exists owing to rapid time-dependent morphology changes at the dealloyed layer/parent phase interface. We discuss the applicability of our findings to the IGSCC of important engineering Fe- and Ni-based alloys in critical applications.

    更新日期:2018-09-11
  • A multicaloric cooling cycle that exploits thermal hysteresis
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-10
    Tino Gottschall, Adrià Gràcia-Condal, Maximilian Fries, Andreas Taubel, Lukas Pfeuffer, Lluís Mañosa, Antoni Planes, Konstantin P. Skokov, Oliver Gutfleisch

    The giant magnetocaloric effect, in which large thermal changes are induced in a material on the application of a magnetic field, can be used for refrigeration applications, such as the cooling of systems from a small to a relatively large scale. However, commercial uptake is limited. We propose an approach to magnetic cooling that rejects the conventional idea that the hysteresis inherent in magnetostructural phase-change materials must be minimized to maximize the reversible magnetocaloric effect. Instead, we introduce a second stimulus, uniaxial stress, so that we can exploit the hysteresis. This allows us to lock-in the ferromagnetic phase as the magnetizing field is removed, which drastically removes the volume of the magnetic field source and so reduces the amount of expensive Nd–Fe–B permanent magnets needed for a magnetic refrigerator. In addition, the mass ratio between the magnetocaloric material and the permanent magnet can be increased, which allows scaling of the cooling power of a device simply by increasing the refrigerant body. The technical feasibility of this hysteresis-positive approach is demonstrated using Ni–Mn–In Heusler alloys. Our study could lead to an enhanced usage of the giant magnetocaloric effect in commercial applications.

    更新日期:2018-09-11
  • Molecularly thin two-dimensional hybrid perovskites with tunable optoelectronic properties due to reversible surface relaxation
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-10
    Kai Leng, Ibrahim Abdelwahab, Ivan Verzhbitskiy, Mykola Telychko, Leiqiang Chu, Wei Fu, Xiao Chi, Na Guo, Zhihui Chen, Zhongxin Chen, Chun Zhang, Qing-Hua Xu, Jiong Lu, Manish Chhowalla, Goki Eda, Kian Ping Loh

    Due to their layered structure, two-dimensional Ruddlesden–Popper perovskites (RPPs), composed of multiple organic/inorganic quantum wells, can in principle be exfoliated down to few and single layers. These molecularly thin layers are expected to present unique properties with respect to the bulk counterpart, due to increased lattice deformations caused by interface strain. Here, we have synthesized centimetre-sized, pure-phase single-crystal RPP perovskites (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1 (n = 1–4) from which single quantum well layers have been exfoliated. We observed a reversible shift in excitonic energies induced by laser annealing on exfoliated layers encapsulated by hexagonal boron nitride. Moreover, a highly efficient photodetector was fabricated using a molecularly thin n = 4 RPP crystal, showing a photogain of 105 and an internal quantum efficiency of ~34%. Our results suggest that, thanks to their dynamic structure, atomically thin perovskites enable an additional degree of control for the bandgap engineering of these materials

    更新日期:2018-09-11
  • Compositional and orientational control in metal halide perovskites of reduced dimensionality
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-10
    Rafael Quintero-Bermudez, Aryeh Gold-Parker, Andrew H. Proppe, Rahim Munir, Zhenyu Yang, Shana O. Kelley, Aram Amassian, Michael F. Toney, Edward H. Sargent

    Reduced-dimensional metal halide perovskites (RDPs) have attracted significant attention in recent years due to their promising light harvesting and emissive properties. We sought to increase the systematic understanding of how RDPs are formed. Here we report that layered intermediate complexes formed with the solvent provide a scaffold that facilitates the nucleation and growth of RDPs during annealing, as observed via in situ X-ray scattering. Transient absorption spectroscopy of RDP single crystals and films enables the identification of the distribution of quantum well thicknesses. These insights allow us to develop a kinetic model of RDP formation that accounts for the experimentally observed size distribution of wells. RDPs exhibit a thickness distribution (with sizes that extend above n = 5) determined largely by the stoichiometric proportion between the intercalating cation and solvent complexes. The results indicate a means to control the distribution, composition and orientation of RDPs via the selection of the intercalating cation, the solvent and the deposition technique.

    更新日期:2018-09-11
  • Author Correction: Efficient electrical detection of mid-infrared graphene plasmons at room temperature
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-10
    Qiushi Guo, Renwen Yu, Cheng Li, Shaofan Yuan, Bingchen Deng, F. Javier García de Abajo, Fengnian Xia

    Author Correction: Efficient electrical detection of mid-infrared graphene plasmons at room temperatureAuthor Correction: Efficient electrical detection of mid-infrared graphene plasmons at room temperature, Published online: 10 September 2018; doi:10.1038/s41563-018-0186-2Author Correction: Efficient electrical detection of mid-infrared graphene plasmons at room temperature

    更新日期:2018-09-10
  • Orbital-selective metals
    Nat. Mater. (IF 39.235) Pub Date : 2018-09-03
    Massimo Capone

    Orbital-selective metalsOrbital-selective metals, Published online: 03 September 2018; doi:10.1038/s41563-018-0173-7The metallic state of an iron chalcogenide superconductor is demonstrated to be characterized by the simultaneous presence of itinerant carriers with different degrees of correlation. This orbital-selective metal arises from a sizeable Hund’s coupling.

    更新日期:2018-09-04
  • Efficient electrical detection of mid-infrared graphene plasmons at room temperature
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-27
    Qiushi Guo, Renwen Yu, Cheng Li, Shaofan Yuan, Bingchen Deng, F. Javier García de Abajo, Fengnian Xia

    Optical excitation and subsequent decay of graphene plasmons can produce a significant increase in charge-carrier temperature. An efficient method to convert this temperature elevation into electrical signals can enable important mid-infrared applications. However, the modest thermoelectric coefficient and weak temperature dependence of carrier transport in graphene hinder this goal. Here, we demonstrate mid-infrared graphene detectors consisting of arrays of plasmonic resonators interconnected by quasi-one-dimensional nanoribbons. Localized barriers associated with disorder in the nanoribbons produce a dramatic temperature dependence of carrier transport, thus enabling the electrical detection of plasmon decay in the nearby graphene resonators. Our device has a subwavelength footprint of 5 × 5 μm2 and operates at 12.2 μm with an external responsivity of 16 mA W–1 and a low noise-equivalent power of 1.3 nW Hz–1/2 at room temperature. It is fabricated using large-scale graphene and possesses a simple two-terminal geometry, representing an essential step towards the realization of an on-chip graphene mid-infrared detector array.

    更新日期:2018-08-27
  • Chemical nature of ferroelastic twin domains in CH3NH3PbI3 perovskite
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-27
    Yongtao Liu, Liam Collins, Roger Proksch, Songkil Kim, Brianna R. Watson, Benjamin Doughty, Tessa R. Calhoun, Mahshid Ahmadi, Anton V. Ievlev, Stephen Jesse, Scott T. Retterer, Alex Belianinov, Kai Xiao, Jingsong Huang, Bobby G. Sumpter, Sergei V. Kalinin, Bin Hu, Olga S. Ovchinnikova

    The extraordinary optoelectronic performance of hybrid organic–inorganic perovskites has resulted in extensive efforts to unravel their properties. Recently, observations of ferroic twin domains in methylammonium lead triiodide drew significant attention as a possible explanation for the current–voltage hysteretic behaviour in these materials. However, the properties of the twin domains, their local chemistry and the chemical impact on optoelectronic performance remain unclear. Here, using multimodal chemical and functional imaging methods, we unveil the mechanical origin of the twin domain contrast observed with piezoresponse force microscopy in methylammonium lead triiodide. By combining experimental results with first principles simulations we reveal an inherent coupling between ferroelastic twin domains and chemical segregation. These results reveal an interplay of ferroic properties and chemical segregation on the optoelectronic performance of hybrid organic–inorganic perovskites, and offer an exploratory path to improving functional devices.

    更新日期:2018-08-27
  • When defects are not defects
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-23
    Arkady V. Krasheninnikov

    When defects are not defectsWhen defects are not defects, Published online: 23 August 2018; doi:10.1038/s41563-018-0153-yLine defects in two-dimensional borophene can self-assemble into new crystalline phases, blurring the distinctions between perfect and defective crystal.

    更新日期:2018-08-23
  • Rolling sound waves
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-23
    Jörn Dunkel

    Rolling sound wavesRolling sound waves, Published online: 23 August 2018; doi:10.1038/s41563-018-0155-9A quantitative description of sound wave propagation in suspensions of self-propelled colloidal particles is achieved by combining microfluidics, video microscopy and theory.

    更新日期:2018-08-23
  • Ferromagnetism in a topological semimetal
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-23
    D. A. Pesin

    Ferromagnetism in a topological semimetalFerromagnetism in a topological semimetal, Published online: 23 August 2018; doi:10.1038/s41563-018-0161-yThe van der Waals material Fe3–xGeTe2 is shown to be a strong candidate for a ferromagnetic nodal-line semimetal with a very large anomalous Hall effect.

    更新日期:2018-08-23
  • Luminal coating of the intestine
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-23
    Gregor Fuhrmann

    Luminal coating of the intestineLuminal coating of the intestine, Published online: 23 August 2018; doi:10.1038/s41563-018-0143-0An orally administered bifunctional gastrointestinal coating has been developed and shown to limit nutrient absorption through the bowel mucosa ultimately lowering blood glucose and also acting as a platform for delivery of drugs to the gastrointestinal tract.

    更新日期:2018-08-23
  • Flesh by design
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-23

    Flesh by designFlesh by design, Published online: 23 August 2018; doi:10.1038/s41563-018-0156-8Treating living matter as a material has immense biomedical potential, but it’s worth acknowledging how the notion unsettles longstanding preconceptions and raises challenging new questions.

    更新日期:2018-08-23
  • Extreme gels
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-23
    Philip Ball

    Extreme gelsExtreme gels, Published online: 23 August 2018; doi:10.1038/s41563-018-0163-9Extreme gels

    更新日期:2018-08-23
  • Publisher Correction: Materials challenges for the Starshot lightsail
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-16
    Harry A. Atwater, Artur R. Davoyan, Ognjen Ilic, Deep Jariwala, Michelle C. Sherrott, Cora M. Went, William S. Whitney, Joeson Wong

    Publisher Correction: Materials challenges for the Starshot lightsailPublisher Correction: Materials challenges for the Starshot lightsail, Published online: 16 August 2018; doi:10.1038/s41563-018-0160-zPublisher Correction: Materials challenges for the Starshot lightsail

    更新日期:2018-08-17
  • Biomaterial-assisted targeted modulation of immune cells in cancer treatment
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-13
    Hua Wang, David J. Mooney

    The past decade has witnessed the accelerating development of immunotherapies for cancer treatment. Immune checkpoint blockade therapies and chimeric antigen receptor (CAR)-T cell therapies have demonstrated clinical efficacy against a variety of cancers. However, issues including life-threatening off-target side effects, long processing times, limited patient responses and high cost still limit the clinical utility of cancer immunotherapies. Biomaterial carriers of these therapies, though, enable one to troubleshoot the delivery issues, amplify immunomodulatory effects, integrate the synergistic effect of different molecules and, more importantly, home and manipulate immune cells in vivo. In this Review, we will analyse thus-far developed immunomaterials for targeted modulation of dendritic cells, T cells, tumour-associated macrophages, myeloid-derived suppressor cells, B cells and natural killer cells, and summarize the promises and challenges of cell-targeted immunomodulation for cancer treatment.

    更新日期:2018-08-13
  • Two-dimensional itinerant ferromagnetism in atomically thin Fe3GeTe2
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-13
    Zaiyao Fei, Bevin Huang, Paul Malinowski, Wenbo Wang, Tiancheng Song, Joshua Sanchez, Wang Yao, Di Xiao, Xiaoyang Zhu, Andrew F. May, Weida Wu, David H. Cobden, Jiun-Haw Chu, Xiaodong Xu

    Discoveries of intrinsic two-dimensional (2D) ferromagnetism in van der Waals (vdW) crystals provide an interesting arena for studying fundamental 2D magnetism and devices that employ localized spins1,2,3,4. However, an exfoliable vdW material that exhibits intrinsic 2D itinerant magnetism remains elusive. Here we demonstrate that Fe3GeTe2 (FGT), an exfoliable vdW magnet, exhibits robust 2D ferromagnetism with strong perpendicular anisotropy when thinned down to a monolayer. Layer-number-dependent studies reveal a crossover from 3D to 2D Ising ferromagnetism for thicknesses less than 4 nm (five layers), accompanied by a fast drop of the Curie temperature (TC) from 207 K to 130 K in the monolayer. For FGT flakes thicker than ~15 nm, a distinct magnetic behaviour emerges in an intermediate temperature range, which we show is due to the formation of labyrinthine domain patterns. Our work introduces an atomically thin ferromagnetic metal that could be useful for the study of controllable 2D itinerant ferromagnetism and for engineering spintronic vdW heterostructures5.

    更新日期:2018-08-13
  • Publisher Correction: The role of reticular chemistry in the design of CO2 reduction catalysts
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-07
    Christian S. Diercks, Yuzhong Liu, Kyle E. Cordova, Omar M. Yaghi

    Publisher Correction: The role of reticular chemistry in the design of CO2 reduction catalysts Publisher Correction: The role of reticular chemistry in the design of CO2 reduction catalysts, Published online: 07 August 2018; doi:10.1038/s41563-018-0159-5 Publisher Correction: The role of reticular chemistry in the design of CO2 reduction catalysts

    更新日期:2018-08-08
  • Quantum spin liquids unveil the genuine Mott state
    Nat. Mater. (IF 39.235) Pub Date : 2018-08-06
    A. Pustogow, M. Bories, A. Löhle, R. Rösslhuber, E. Zhukova, B. Gorshunov, S. Tomić, J. A. Schlueter, R. Hübner, T. Hiramatsu, Y. Yoshida, G. Saito, R. Kato, T.-H. Lee, V. Dobrosavljević, S. Fratini, M. Dressel

    The localization of charge carriers by electronic repulsion was suggested by Mott in the 1930s to explain the insulating state observed in supposedly metallic NiO. The Mott metal–insulator transition has been subject of intense investigations ever since1,2,3—not least for its relation to high-temperature superconductivity4. A detailed comparison to real materials, however, is lacking because the pristine Mott state is commonly obscured by antiferromagnetism and a complicated band structure. Here we study organic quantum spin liquids, prototype realizations of the single-band Hubbard model in the absence of magnetic order. Mapping the Hubbard bands by optical spectroscopy provides an absolute measure of the interaction strength and bandwidth—the crucial parameters that enter calculations. In this way, we advance beyond conventional temperature–pressure plots and quantitatively compose a generic phase diagram for all genuine Mott insulators based on the absolute strength of the electronic correlations. We also identify metallic quantum fluctuations as a precursor of the Mott insulator–metal transition, previously predicted but never observed. Our results suggest that all relevant phenomena in the phase diagram scale with the Coulomb repulsion U, which provides a direct link to unconventional superconductivity in cuprates and other strongly correlated materials.

    更新日期:2018-08-06
  • Switching by topological insulators
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-30
    Chi-Feng Pai

    Switching by topological insulatorsSwitching by topological insulators, Published online: 30 July 2018; doi:10.1038/s41563-018-0146-xMagnetization in magnetoresistive memory devices can be controlled at room temperature by spin–orbit torques originating from the surface states of topological insulators.

    更新日期:2018-07-31
  • A conductive topological insulator with large spin Hall effect for ultralow power spin–orbit torque switching
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-30
    Nguyen Huynh Duy Khang, Yugo Ueda, Pham Nam Hai

    Spin–orbit torque switching using the spin Hall effect in heavy metals and topological insulators has a great potential for ultralow power magnetoresistive random-access memory. To be competitive with conventional spin-transfer torque switching, a pure spin current source with a large spin Hall angle (θSH > 1) and high electrical conductivity (σ > 105 Ω−1 m−1) is required. Here we demonstrate such a pure spin current source: conductive topological insulator BiSb thin films with σ ≈ 2.5 × 105 Ω−1 m−1, θSH ≈ 52 and spin Hall conductivity σSH ≈ 1.3 × 107 ℏ2eΩ−1 m−1 at room temperature. We show that BiSb thin films can generate a very large spin–orbit field of 2.3 kOe MA–1 cm2 and a critical switching current density as low as 1.5 MA cm–2 in Bi0.9Sb0.1/MnGa bilayers, which underlines the potential of BiSb for industrial applications.

    更新日期:2018-07-31
  • Robust microscale superlubricity in graphite/hexagonal boron nitride layered heterojunctions
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-30
    Yiming Song, Davide Mandelli, Oded Hod, Michael Urbakh, Ming Ma, Quanshui Zheng

    Structural superlubricity is a fascinating tribological phenomenon, in which the lateral interactions between two incommensurate contacting surfaces are effectively cancelled resulting in ultralow sliding friction. Here we report the experimental realization of robust superlubricity in microscale monocrystalline heterojunctions, which constitutes an important step towards the macroscopic scale-up of superlubricity. The results for interfaces between graphite and hexagonal boron nitride clearly demonstrate that structural superlubricity persists even when the aligned contact sustains external loads under ambient conditions. The observed frictional anisotropy in the heterojunctions is found to be orders of magnitude smaller than that measured for their homogeneous counterparts. Atomistic simulations reveal that the underlying frictional mechanisms in the two cases originate from completely different dynamical regimes. Our results are expected to be of a general nature and should be applicable to other van der Waals heterostructures.

    更新日期:2018-07-31
  • Room-temperature high spin–orbit torque due to quantum confinement in sputtered BixSe(1–x) films
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-30
    Mahendra DC, Roberto Grassi, Jun-Yang Chen, Mahdi Jamali, Danielle Reifsnyder Hickey, Delin Zhang, Zhengyang Zhao, Hongshi Li, P. Quarterman, Yang Lv, Mo Li, Aurelien Manchon, K. Andre Mkhoyan, Tony Low, Jian-Ping Wang

    The spin–orbit torque (SOT) that arises from materials with large spin–orbit coupling promises a path for ultralow power and fast magnetic-based storage and computational devices. We investigated the SOT from magnetron-sputtered BixSe(1–x) thin films in BixSe(1–x)/Co20Fe60B20 heterostructures by using d.c. planar Hall and spin-torque ferromagnetic resonance (ST-FMR) methods. Remarkably, the spin torque efficiency (θS) was determined to be as large as 18.62 ± 0.13 and 8.67 ± 1.08 using the d.c. planar Hall and ST-FMR methods, respectively. Moreover, switching of the perpendicular CoFeB multilayers using the SOT from the BixSe(1–x) was observed at room temperature with a low critical magnetization switching current density of 4.3 × 105 A cm–2. Quantum transport simulations using a realistic sp3 tight-binding model suggests that the high SOT in sputtered BixSe(1–x) is due to the quantum confinement effect with a charge-to-spin conversion efficiency that enhances with reduced size and dimensionality. The demonstrated θS, ease of growth of the films on a silicon substrate and successful growth and switching of perpendicular CoFeB multilayers on BixSe(1–x) films provide an avenue for the use of BixSe(1–x) as a spin density generator in SOT-based memory and logic devices.

    更新日期:2018-07-31
  • Learning from scratch
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-24
    Philip Ball

    Learning from scratch Learning from scratch, Published online: 24 July 2018; doi:10.1038/s41563-018-0142-1 Learning from scratch

    更新日期:2018-07-24
  • Upping the ante
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-24

    Upping the ante Upping the ante, Published online: 24 July 2018; doi:10.1038/s41563-018-0148-8 Lessons learnt from Horizon 2020 and a determination to become a world-class hub for entrepreneurship form the basis of the European Commission’s ambitious Research and Innovation budget.

    更新日期:2018-07-24
  • A tale about square dancers and maze runners
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-24
    Matthias Weiss

    A tale about square dancers and maze runners A tale about square dancers and maze runners, Published online: 24 July 2018; doi:10.1038/s41563-018-0126-1 Single-particle tracking of nanoparticles dispersed in the cytoplasm of living cells shows that non-specific interactions with the intracellular environment are the major contributors for the anomalous diffusion characteristics of intracellular motion.

    更新日期:2018-07-24
  • Charge crystallization in a Fermi liquid
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-24
    Jonathan Pelliciari, Riccardo Comin

    Charge crystallization in a Fermi liquid Charge crystallization in a Fermi liquid, Published online: 24 July 2018; doi:10.1038/s41563-018-0139-9 Charge order has been established as a ubiquitous instability of the underdoped copper-oxide superconductors. New investigations reveal that it extends to the overdoped side of the phase diagram, a region otherwise known to host a conventional Fermi liquid state.

    更新日期:2018-07-24
  • More than electrons
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-24
    Kai Rossnagel

    More than electrons More than electrons, Published online: 24 July 2018; doi:10.1038/s41563-018-0131-4 Angle-resolved photoemission spectroscopy of MoS2 doped with Rb atoms unveiled the existence of polarons, whose presence seems to coincide with the onset of superconductivity.

    更新日期:2018-07-24
  • Simultaneous coherence enhancement of optical and microwave transitions in solid-state electronic spins
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-23
    Antonio Ortu, Alexey Tiranov, Sacha Welinski, Florian Fröwis, Nicolas Gisin, Alban Ferrier, Philippe Goldner, Mikael Afzelius

    Solid-state electronic spins are extensively studied in quantum information science, as their large magnetic moments offer fast operations for computing1 and communication2,3,4, and high sensitivity for sensing5. However, electronic spins are more sensitive to magnetic noise, but engineering of their spectroscopic properties, for example, using clock transitions and isotopic engineering, can yield remarkable spin coherence times, as for electronic spins in GaAs6, donors in silicon7,8,9,10,11 and vacancy centres in diamond12,13. Here we demonstrate simultaneously induced clock transitions for both microwave and optical domains in an isotopically purified 171Yb3+:Y2SiO5 crystal, reaching coherence times of greater than 100 μs and 1 ms in the optical and microwave domains, respectively. This effect is due to the highly anisotropic hyperfine interaction, which makes each electronic–nuclear state an entangled Bell state. Our results underline the potential of 171Yb3+:Y2SiO5 for quantum processing applications relying on both optical and spin manipulation, such as optical quantum memories4,14, microwave-to-optical quantum transducers15,16, and single-spin detection17, while they should also be observable in a range of different materials with anisotropic hyperfine interactions.

    更新日期:2018-07-24
  • Large anomalous Hall current induced by topological nodal lines in a ferromagnetic van der Waals semimetal
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-16
    Kyoo Kim, Junho Seo, Eunwoo Lee, K.-T. Ko, B. S. Kim, Bo Gyu Jang, Jong Mok Ok, Jinwon Lee, Youn Jung Jo, Woun Kang, Ji Hoon Shim, C. Kim, Han Woong Yeom, Byung Il Min, Bohm-Jung Yang, Jun Sung Kim

    Topological semimetals host electronic structures with several band-contact points or lines and are generally expected to exhibit strong topological responses. Up to now, most work has been limited to non-magnetic materials and the interplay between topology and magnetism in this class of quantum materials has been largely unexplored. Here we utilize theoretical calculations, magnetotransport and angle-resolved photoemission spectroscopy to propose Fe3GeTe2, a van der Waals material, as a candidate ferromagnetic (FM) nodal line semimetal. We find that the spin degree of freedom is fully quenched by the large FM polarization, but the line degeneracy is protected by crystalline symmetries that connect two orbitals in adjacent layers. This orbital-driven nodal line is tunable by spin orientation due to spin–orbit coupling and produces a large Berry curvature, which leads to a large anomalous Hall current, angle and factor. These results demonstrate that FM topological semimetals hold significant potential for spin- and orbital-dependent electronic functionalities.

    更新日期:2018-07-18
  • Structural evolution of titanium dioxide during reduction in high-pressure hydrogen
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-16
    Sencer Selcuk, Xunhua Zhao, Annabella Selloni

    The excellent photocatalytic properties of titanium oxide (TiO2) under ultraviolet light have long motivated the search for doping strategies capable of extending its photoactivity to the visible part of the spectrum. One approach is high-pressure and high-temperature hydrogenation, which results in reduced ‘black TiO2’ nanoparticles with a crystalline core and a disordered shell that absorbs visible light. Here we elucidate the formation mechanism and structural features of black TiO2 using first-principles-validated reactive force field molecular dynamics simulations of anatase TiO2 surfaces and nanoparticles at high temperature and under high hydrogen pressures. Simulations reveal that surface oxygen vacancies created upon reaction of H2 with surface oxygen atoms diffuse towards the bulk material but encounter a high barrier for subsurface migration on {001} facets of the nanoparticles, which initiates surface disordering. Besides confirming that the hydrogenated amorphous shell has a key role in the photoactivity of black TiO2, our results provide insight into the properties of the disordered surface layers that are observed on regular anatase nanocrystals under photocatalytic water-splitting conditions.

    更新日期:2018-07-18
  • Design rules for minimizing voltage losses in high-efficiency organic solar cells
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-16
    Deping Qian, Zilong Zheng, Huifeng Yao, Wolfgang Tress, Thomas R. Hopper, Shula Chen, Sunsun Li, Jing Liu, Shangshang Chen, Jiangbin Zhang, Xiao-Ke Liu, Bowei Gao, Liangqi Ouyang, Yingzhi Jin, Galia Pozina, Irina A. Buyanova, Weimin M. Chen, Olle Inganäs, Veaceslav Coropceanu, Jean-Luc Bredas, He Yan, Jianhui Hou, Fengling Zhang, Artem A. Bakulin, Feng Gao

    The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps. Energy losses during charge separation at the donor–acceptor interface and non-radiative recombination are among the main causes of such voltage losses. Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend. Following these rules, we present a range of existing and new donor–acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 0.03%, leading to non-radiative voltage losses as small as 0.21 V. This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells.

    更新日期:2018-07-18
  • Surface distortion as a unifying concept and descriptor in oxygen reduction reaction electrocatalysis
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-16
    Raphaël Chattot, Olivier Le Bacq, Vera Beermann, Stefanie Kühl, Juan Herranz, Sebastian Henning, Laura Kühn, Tristan Asset, Laure Guétaz, Gilles Renou, Jakub Drnec, Pierre Bordet, Alain Pasturel, Alexander Eychmüller, Thomas J. Schmidt, Peter Strasser, Laetitia Dubau, Frédéric Maillard

    Tuning the surface structure at the atomic level is of primary importance to simultaneously meet the electrocatalytic performance and stability criteria required for the development of low-temperature proton-exchange membrane fuel cells (PEMFCs). However, transposing the knowledge acquired on extended, model surfaces to practical nanomaterials remains highly challenging. Here, we propose ‘surface distortion’ as a novel structural descriptor, which is able to reconciliate and unify seemingly opposing notions and contradictory experimental observations in regards to the electrocatalytic oxygen reduction reaction (ORR) reactivity. Beyond its unifying character, we show that surface distortion is pivotal to rationalize the electrocatalytic properties of state-of-the-art of PtNi/C nanocatalysts with distinct atomic composition, size, shape and degree of surface defectiveness under a simulated PEMFC cathode environment. Our study brings fundamental and practical insights into the role of surface defects in electrocatalysis and highlights strategies to design more durable ORR nanocatalysts.

    更新日期:2018-07-18
  • Intermixing and periodic self-assembly of borophene line defects
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-16
    Xiaolong Liu, Zhuhua Zhang, Luqing Wang, Boris I. Yakobson, Mark C. Hersam

    Two-dimensional (2D) boron (that is, borophene) was recently synthesized following theoretical predictions1,2,3,4,5. Its metallic nature and high in-plane anisotropy combine many of the desirable attributes of graphene6 and monolayer black phosphorus7. As a synthetic 2D material, its structural properties cannot be deduced from bulk boron, which implies that the intrinsic defects of borophene remain unexplored. Here we investigate borophene line defects at the atomic scale with ultrahigh vacuum (UHV) scanning tunnelling microscopy/spectroscopy (STM/STS) and density functional theory (DFT). Under suitable growth conditions, borophene phases that correspond to the v1/6 and v1/5 models are found to intermix and accommodate line defects in each other with structures that match the constituent units of the other phase. These line defects energetically favour spatially periodic self-assembly that gives rise to new borophene phases, which ultimately blurs the distinction between borophene crystals and defects. This phenomenon is unique to borophene as a result of its high in-plane anisotropy and energetically and structurally similar polymorphs. Low-temperature measurements further reveal subtle electronic features that are consistent with a charge density wave (CDW), which are modulated by line defects. This atomic-level understanding is likely to inform ongoing efforts to devise and realize applications based on borophene.

    更新日期:2018-07-18
  • Publisher Correction: Carbon nanotubes as emerging quantum-light sources
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-11
    X. He, H. Htoon, S. K. Doorn, W. H. P. Pernice, F. Pyatkov, R. Krupke, A. Jeantet, Y. Chassagneux, C. Voisin

    Publisher Correction: Carbon nanotubes as emerging quantum-light sources Publisher Correction: Carbon nanotubes as emerging quantum-light sources, Published online: 11 July 2018; doi:10.1038/s41563-018-0141-2 Publisher Correction: Carbon nanotubes as emerging quantum-light sources

    更新日期:2018-07-12
  • Impacts of surface depletion on the plasmonic properties of doped semiconductor nanocrystals
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-09
    Omid Zandi, Ankit Agrawal, Alex B. Shearer, Lauren C. Reimnitz, Clayton J. Dahlman, Corey M. Staller, Delia J. Milliron

    Degenerately doped semiconductor nanocrystals (NCs) exhibit a localized surface plasmon resonance (LSPR) in the infrared range of the electromagnetic spectrum. Unlike metals, semiconductor NCs offer tunable LSPR characteristics enabled by doping, or via electrochemical or photochemical charging. Tuning plasmonic properties through carrier density modulation suggests potential applications in smart optoelectronics, catalysis and sensing. Here, we elucidate fundamental aspects of LSPR modulation through dynamic carrier density tuning in Sn-doped In2O3 (Sn:In2O3) NCs. Monodisperse Sn:In2O3 NCs with various doping levels and sizes were synthesized and assembled in uniform films. NC films were then charged in an in situ electrochemical cell and the LSPR modulation spectra were monitored. Based on spectral shifts and intensity modulation of the LSPR, combined with optical modelling, it was found that often-neglected semiconductor properties, specifically band structure modification due to doping and surface states, strongly affect LSPR modulation. Fermi level pinning by surface defect states creates a surface depletion layer that alters the LSPR properties; it determines the extent of LSPR frequency modulation, diminishes the expected near-field enhancement, and strongly reduces sensitivity of the LSPR to the surroundings.

    更新日期:2018-07-10
  • Publisher Correction: Symmetry and magnetism allied
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-09
    Manfred Fiebig

    Publisher Correction: Symmetry and magnetism alliedPublisher Correction: Symmetry and magnetism allied, Published online: 09 July 2018; doi:10.1038/s41563-018-0145-yPublisher Correction: Symmetry and magnetism allied

    更新日期:2018-07-09
  • Coupling two order parameters in a quantum gas
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-02
    Andrea Morales, Philip Zupancic, Julian Léonard, Tilman Esslinger, Tobias Donner

    Controlling matter to simultaneously support coupled properties is of fundamental and technological importance1 (for example, in multiferroics2,3,4,5 or high-temperature superconductors6,7,8,9). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology10,11 or modify properties12,13,14,15,16. Here, using a quantum gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators17, resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore quantum tricritical points18 and can be extended to study the interplay of spin and density orders19 as a function of temperature20.

    更新日期:2018-07-02
  • Non-specific interactions govern cytosolic diffusion of nanosized objects in mammalian cells
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-02
    Fred Etoc, Elie Balloul, Chiara Vicario, Davide Normanno, Domenik Liße, Assa Sittner, Jacob Piehler, Maxime Dahan, Mathieu Coppey

    The diffusivity of macromolecules in the cytoplasm of eukaryotic cells varies over orders of magnitude and dictates the kinetics of cellular processes. However, a general description that associates the Brownian or anomalous nature of intracellular diffusion to the architectural and biochemical properties of the cytoplasm has not been achieved. Here we measure the mobility of individual fluorescent nanoparticles in living mammalian cells to obtain a comprehensive analysis of cytoplasmic diffusion. We identify a correlation between tracer size, its biochemical nature and its mobility. Inert particles with size equal or below 50 nm behave as Brownian particles diffusing in a medium of low viscosity with negligible effects of molecular crowding. Increasing the strength of non-specific interactions of the nanoparticles within the cytoplasm gradually reduces their mobility and leads to subdiffusive behaviour. These experimental observations and the transition from Brownian to subdiffusive motion can be captured in a minimal phenomenological model.

    更新日期:2018-07-02
  • Sounds and hydrodynamics of polar active fluids
    Nat. Mater. (IF 39.235) Pub Date : 2018-07-02
    Delphine Geyer, Alexandre Morin, Denis Bartolo

    Spontaneously flowing liquids have been successfully engineered from a variety of biological and synthetic self-propelled units1,2,3,4,5,6,7,8,9,10,11. Together with their orientational order, wave propagation in such active fluids has remained a subject of intense theoretical studies12,13,14,15,16,17. However, the experimental observation of this phenomenon has remained elusive. Here, we establish and exploit the propagation of sound waves in colloidal active materials with broken rotational symmetry. We demonstrate that two mixed modes, coupling density and velocity fluctuations, propagate along all directions in colloidal-roller fluids. We then show how the six material constants defining the linear hydrodynamics of these active liquids can be measured from their spontaneous fluctuation spectrum, while being out of reach of conventional rheological methods. This active-sound spectroscopy is not specific to synthetic active materials and could provide a quantitative hydrodynamic description of herds, flocks and swarms from inspection of their large-scale fluctuations18,19,20,21.

    更新日期:2018-07-02
  • Pure spin currents find the off switch
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    Peter Wadley

    Pure spin currents find the off switchPure spin currents find the off switch, Published online: 25 June 2018; doi:10.1038/s41563-018-0125-2A means of reversibly switching spin conductance on or off is demonstrated and brings spintronics using pure spin currents — a prime candidate for the next generation of low-power microelectronic devices — a step closer.

    更新日期:2018-06-27
  • Long-range symmetry breaking in embedded ferroelectrics
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    Hugh Simons, Astri Bjørnetun Haugen, Anders Clemen Jakobsen, Søren Schmidt, Frederik Stöhr, Marta Majkut, Carsten Detlefs, John E. Daniels, Dragan Damjanovic, Henning Friis Poulsen

    The characteristic functionality of ferroelectric materials is due to the symmetry of their crystalline structure. As such, ferroelectrics lend themselves to design approaches that manipulate this structural symmetry by introducing extrinsic strain. Using in situ dark-field X-ray microscopy to map lattice distortions around deeply embedded domain walls and grain boundaries in BaTiO3, we reveal that symmetry-breaking strain fields extend up to several micrometres from domain walls. As this exceeds the average domain width, no part of the material is elastically relaxed, and symmetry is universally broken. Such extrinsic strains are pivotal in defining the local properties and self-organization of embedded domain walls, and must be accounted for by emerging computational approaches to material design.

    更新日期:2018-06-27
  • Mechanics-guided developmental fate patterning
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    Mukul Tewary, Peter W. Zandstra

    Mechanics-guided developmental fate patterningMechanics-guided developmental fate patterning, Published online: 25 June 2018; doi:10.1038/s41563-018-0121-6A micropatterned human pluripotent stem cell-based developmental model was utilized to demonstrate the role of biophysical cues such as cell size and cytoskeletal contractile forces in directing patterning of neuroepithelial and neural plate border cells.

    更新日期:2018-06-27
  • Seeing the forest and the trees
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    Hiroyuki Takenaka, Ilya Grinberg, Andrew M. Rappe

    Seeing the forest and the treesSeeing the forest and the trees, Published online: 25 June 2018; doi:10.1038/s41563-018-0117-2A paradigm relating ultrahigh piezoelectricity and multiscale inhomogeneous structure in relaxor ferroelectrics emerges from state-of-the-art neutron and X-ray diffuse scattering measurements.

    更新日期:2018-06-27
  • Biomaterials driving repair after stroke
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    Anup Tuladhar, Molly S. Shoichet

    Biomaterials driving repair after strokeBiomaterials driving repair after stroke, Published online: 25 June 2018; doi:10.1038/s41563-018-0124-3An injectable biomaterial with angiogenic and immune-modulatory properties was developed and shown to support brain tissue repair and functional recovery in a mouse model of stroke.

    更新日期:2018-06-27
  • Hydrogen to the rescue
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25

    Hydrogen to the rescueHydrogen to the rescue, Published online: 25 June 2018; doi:10.1038/s41563-018-0129-yLarge-scale, environmentally friendly hydrogen production will rely on steam methane reforming coupled with carbon capture and electrolysis, but solar fuels could have a disruptive role to play.

    更新日期:2018-06-27
  • The relation of local order to material properties in relaxor ferroelectrics
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    M. J. Krogstad, P. M. Gehring, S. Rosenkranz, R. Osborn, F. Ye, Y. Liu, J. P. C. Ruff, W. Chen, J. M. Wozniak, H. Luo, O. Chmaissem, Z.-G. Ye, D. Phelan

    Correlating electromechanical and dielectric properties with nanometre-scale order is the defining challenge for the development of piezoelectric oxides. Current lead (Pb)-based relaxor ferroelectrics can serve as model systems with which to unravel these correlations, but the nature of the local order and its relation to material properties remains controversial. Here we employ recent advances in diffuse scattering instrumentation to investigate crystals that span the phase diagram of PbMg1/3Nb2/3O3-xPbTiO3 (PMN-xPT) and identify four forms of local order. From the compositional dependence, we resolve the coupling of each form to the dielectric and electromechanical properties observed. We show that relaxor behaviour does not correlate simply with ferroic diffuse scattering; instead, it results from a competition between local antiferroelectric correlations, seeded by chemical short-range order, and local ferroic order. The ferroic diffuse scattering is strongest where piezoelectricity is maximal and displays previously unrecognized modulations caused by anion displacements. Our observations provide new guidelines for evaluating displacive models and hence the piezoelectric properties of environmentally friendly next-generation materials.

    更新日期:2018-06-27
  • Out of step with time
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-25
    Philip Ball

    Out of step with timeOut of step with time, Published online: 25 June 2018; doi:10.1038/s41563-018-0127-0Out of step with time

    更新日期:2018-06-27
  • Monatomic phase change memory
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-18
    Martin Salinga, Benedikt Kersting, Ider Ronneberger, Vara Prasad Jonnalagadda, Xuan Thang Vu, Manuel Le Gallo, Iason Giannopoulos, Oana Cojocaru-Mirédin, Riccardo Mazzarello, Abu Sebastian

    Phase change memory has been developed into a mature technology capable of storing information in a fast and non-volatile way1,2,3, with potential for neuromorphic computing applications4,5,6. However, its future impact in electronics depends crucially on how the materials at the core of this technology adapt to the requirements arising from continued scaling towards higher device densities. A common strategy to fine-tune the properties of phase change memory materials, reaching reasonable thermal stability in optical data storage, relies on mixing precise amounts of different dopants, resulting often in quaternary or even more complicated compounds6,7,8. Here we show how the simplest material imaginable, a single element (in this case, antimony), can become a valid alternative when confined in extremely small volumes. This compositional simplification eliminates problems related to unwanted deviations from the optimized stoichiometry in the switching volume, which become increasingly pressing when devices are aggressively miniaturized9,10. Removing compositional optimization issues may allow one to capitalize on nanosize effects in information storage.

    更新日期:2018-06-18
  • Symmetry and magnetism allied
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-18
    Manfred Fiebig

    Symmetry and magnetism allied Symmetry and magnetism allied, Published online: 18 June 2018; doi:10.1038/s41563-018-0113-6 By transferring the symmetry conditions of electric polarization patterns to the field of magnetism, a particularly stable magnetic configuration is obtained that could be interesting for voltage-controlled magnetic devices.

    更新日期:2018-06-18
  • Carbon nanotubes as emerging quantum-light sources
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-18
    X. He, H. Htoon, S. K. Doorn, W. H. P. Pernice, F. Pyatkov, R. Krupke, A. Jeantet, Y. Chassagneux, C. Voisin

    Progress in quantum computing and quantum cryptography requires efficient, electrically triggered, single-photon sources at room temperature in the telecom wavelengths. It has been long known that semiconducting single-wall carbon nanotubes (SWCNTs) display strong excitonic binding and emit light over a broad range of wavelengths, but their use has been hampered by a low quantum yield and a high sensitivity to spectral diffusion and blinking. In this Perspective, we discuss recent advances in the mastering of SWCNT optical properties by chemistry, electrical contacting and resonator coupling towards advancing their use as quantum light sources. We describe the latest results in terms of single-photon purity, generation efficiency and indistinguishability. Finally, we consider the main fundamental challenges stemming from the unique properties of SWCNTs and the most promising roads for SWCNT-based chip integrated quantum photonic sources.

    更新日期:2018-06-18
  • Single-element glass to record data
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-18
    Wei Zhang, Evan Ma

    Single-element glass to record data Single-element glass to record data, Published online: 18 June 2018; doi:10.1038/s41563-018-0114-5 Monatomic glassy antimony can now be achieved via melt-quenching in a nanoconfined volume in a device setting. In contrast to alloys currently used in phase-change memories, deviation from optimized composition is no longer an issue in this simple material.

    更新日期:2018-06-18
  • Observation of magnetic vortex pairs at room temperature in a planar α-Fe2O3/Co heterostructure
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-18
    F. P. Chmiel, N. Waterfield Price, R. D. Johnson, A. D. Lamirand, J. Schad, G. van der Laan, D. T. Harris, J. Irwin, M. S. Rzchowski, C.-B. Eom, P. G. Radaelli

    Vortices, occurring whenever a flow field ‘whirls’ around a one-dimensional core, are among the simplest topological structures, ubiquitous to many branches of physics. In the crystalline state, vortex formation is rare, since it is generally hampered by long-range interactions: in ferroic materials (ferromagnetic and ferroelectric), vortices are observed only when the effects of the dipole–dipole interaction are modified by confinement at the nanoscale1,2,3, or when the parameter associated with the vorticity does not couple directly with strain4. Here, we observe an unprecedented form of vortices in antiferromagnetic haematite (α-Fe2O3) epitaxial films, in which the primary whirling parameter is the staggered magnetization. Remarkably, ferromagnetic topological objects with the same vorticity and winding number as the α-Fe2O3 vortices are imprinted onto an ultra-thin Co ferromagnetic over-layer by interfacial exchange. Our data suggest that the ferromagnetic vortices may be merons (half-skyrmions, carrying an out-of plane core magnetization), and indicate that the vortex/meron pairs can be manipulated by the application of an in-plane magnetic field, giving rise to large-scale vortex–antivortex annihilation.

    更新日期:2018-06-18
  • Perovskites cover silicon textures
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-11
    Anita Ho-Baillie

    Perovskites cover silicon textures Perovskites cover silicon textures, Published online: 11 June 2018; doi:10.1038/s41563-018-0122-5 A two-step deposition method has been developed that enables the conformal coating of textured surfaces with perovskite films. This allows the realization of perovskite/silicon tandem solar cells with increased short-circuit current density.

    更新日期:2018-06-12
  • Therapeutic luminal coating of the intestine
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-11
    Yuhan Lee, Tara E. Deelman, Keyue Chen, Dawn S. Y. Lin, Ali Tavakkoli, Jeffrey M. Karp

    The gastrointestinal tract is the site of most drug delivery and therapeutic interventions for the management and treatment of numerous diseases. However, selective access to its mucosa, especially in the small bowel, is challenging. Here we develop an orally administered gut-coating formulation that provides a transient coating of the bowel. Through a materials screening campaign, we identified a sucrose octasulfate aluminium complex and further engineered the pH-dependent material into a complex coacervate formulation linked via pH-independent electrostatic interaction, which allowed an effective transient physical coating on the gastrointestinal mucosa, independent of gastric acid exposure. We tested the therapeutic values of this technology in two settings. Oral administration of this gut-coating formulation modulated the nutrient contact with bowel mucosa, which lowered the glucose responses in rodent models indicating a potential therapeutic utility in diabetes. Furthermore, the formulation protected biological agents from gastric acid exposure and degradation, which enabled oral delivery to the small bowel mucosa.

    更新日期:2018-06-12
  • Reversible adsorption of nitrogen dioxide within a robust porous metal–organic framework
    Nat. Mater. (IF 39.235) Pub Date : 2018-06-11
    Xue Han, Harry G. W. Godfrey, Lydia Briggs, Andrew J. Davies, Yongqiang Cheng, Luke L. Daemen, Alena M. Sheveleva, Floriana Tuna, Eric J. L. McInnes, Junliang Sun, Christina Drathen, Michael W. George, Anibal J. Ramirez-Cuesta, K. Mark Thomas, Sihai Yang, Martin Schröder

    Nitrogen dioxide (NO2) is a major air pollutant causing significant environmental1,2 and health problems3,4. We report reversible adsorption of NO2 in a robust metal–organic framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO2 isotherm uptake of 14.1 mmol g−1, and, more importantly, exceptional selective removal of low-concentration NO2 (5,000 to <1 ppm) from gas mixtures. Complementary experiments reveal five types of supramolecular interaction that cooperatively bind both NO2 and N2O4 molecules within MFM-300(Al). We find that the in situ equilibrium 2NO2 ↔ N2O4 within the pores is pressure-independent, whereas ex situ this equilibrium is an exemplary pressure-dependent first-order process. The coexistence of helical monomer–dimer chains of NO2 in MFM-300(Al) could provide a foundation for the fundamental understanding of the chemical properties of guest molecules within porous hosts. This work may pave the way for the development of future capture and conversion technologies.

    更新日期:2018-06-12
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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