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  • Realizing the classical XY Hamiltonian in polariton simulators
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-25
    Natalia G. Berloff, Matteo Silva, Kirill Kalinin, Alexis Askitopoulos, Julian D. Töpfer, Pasquale Cilibrizzi, Wolfgang Langbein, Pavlos G. Lagoudakis

    The vast majority of real-life optimization problems with a large number of degrees of freedom are intractable by classical computers, since their complexity grows exponentially fast with the number of variables. Many of these problems can be mapped into classical spin models, such as the Ising, the XY or the Heisenberg models, so that optimization problems are reduced to finding the global minimum of spin models. Here, we propose and investigate the potential of polariton graphs as an efficient analogue simulator for finding the global minimum of the XY model. By imprinting polariton condensate lattices of bespoke geometries we show that we can engineer various coupling strengths between the lattice sites and read out the result of the global minimization through the relative phases. Besides solving optimization problems, polariton graphs can simulate a large variety of systems undergoing the U(1) symmetry-breaking transition. We realize various magnetic phases, such as ferromagnetic, anti-ferromagnetic, and frustrated spin configurations on a linear chain, the unit cells of square and triangular lattices, a disordered graph, and demonstrate the potential for size scalability on an extended square lattice of 45 coherently coupled polariton condensates. Our results provide a route to study unconventional superfluids, spin liquids, Berezinskii–Kosterlitz–Thouless phase transition, and classical magnetism, among the many systems that are described by the XY Hamiltonian.

    更新日期:2017-09-25
  • Evidence for magnetic Weyl fermions in a correlated metal
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-25
    K. Kuroda, T. Tomita, M.-T. Suzuki, C. Bareille, A. A. Nugroho, P. Goswami, M. Ochi, M. Ikhlas, M. Nakayama, S. Akebi, R. Noguchi, R. Ishii, N. Inami, K. Ono, H. Kumigashira, A. Varykhalov, T. Muro, T. Koretsune, R. Arita, S. Shin, Takeshi Kondo, S. Nakatsuji

    Evidence for magnetic Weyl fermions in a correlated metalNature Materials, Published online: 25 September 2017; doi:10.1038/nmat4987Experimental evidence for the realization of magnetic Weyl fermions in the strongly correlated metal Mn3Sn is reported.

    更新日期:2017-09-25
  • Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-25
    Kab-Jin Kim, Se Kwon Kim, Yuushou Hirata, Se-Hyeok Oh, Takayuki Tono, Duck-Ho Kim, Takaya Okuno, Woo Seung Ham, Sanghoon Kim, Gyoungchoon Go, Yaroslav Tserkovnyak, Arata Tsukamoto, Takahiro Moriyama, Kyung-Jin Lee, Teruo Ono

    Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnetsNature Materials, Published online: 25 September 2017; doi:10.1038/nmat4990Fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnetic Gd23Fe67.4Co9.6 thin films at the angular momentum compensation point. In particular, at this point, the field-driven domain wall mobility is found to be enhanced.

    更新日期:2017-09-25
  • Resolving ultrafast exciton migration in organic solids at the nanoscale
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-18
    Samuel B. Penwell, Lucas D. S. Ginsberg, Rodrigo Noriega, Naomi S. Ginsberg

    Effectiveness of molecular-based light harvesting relies on transport of excitons to charge-transfer sites. Measuring exciton migration, however, has been challenging because of the mismatch between nanoscale migration lengths and the diffraction limit. Instead of using bulk substrate quenching methods, here we define quenching boundaries all-optically with sub-diffraction resolution, thus characterizing spatiotemporal exciton migration on its native nanometre and picosecond scales. By transforming stimulated emission depletion microscopy into a time-resolved ultrafast approach, we measure a 16-nm migration length in poly(2,5-di(hexyloxy)cyanoterephthalylidene) conjugated polymer films. Combined with Monte Carlo exciton hopping simulations, we show that migration in these films is essentially diffusive because intrinsic chromophore energetic disorder is comparable to chromophore inhomogeneous broadening. Our approach will enable previously unattainable correlation of local material structure to exciton migration character, applicable not only to photovoltaic or display-destined organic semiconductors but also to explaining the quintessential exciton migration exhibited in photosynthesis.

    更新日期:2017-09-21
  • Self-replication: Nanostructure evolution
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-18
    Friedrich C. Simmel

    Self-replication: Nanostructure evolutionNature Materials, Published online: 18 September 2017; doi:10.1038/nmat4995DNA origami nanostructures were utilized to replicate a seed pattern that resulted in the growth of populations of nanostructures. Exponential growth could be controlled by environmental conditions depending on the preferential requirements of each population.

    更新日期:2017-09-21
  • Imaging and tuning polarity at SrTiO3 domain walls
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-18
    Yiftach Frenkel, Noam Haham, Yishai Shperber, Christopher Bell, Yanwu Xie, Zhuoyu Chen, Yasuyuki Hikita, Harold Y. Hwang, Ekhard K. H. Salje, Beena Kalisky

    Electrostatic fields tune the ground state of interfaces between complex oxide materials. Electronic properties, such as conductivity and superconductivity, can be tuned and then used to create and control circuit elements and gate-defined devices. Here we show that naturally occurring twin boundaries, with properties that are different from their surrounding bulk, can tune the LaAlO3/SrTiO3 interface 2DEG at the nanoscale. In particular, SrTiO3 domain boundaries have the unusual distinction of remaining highly mobile down to low temperatures, and were recently suggested to be polar. Here we apply localized pressure to an individual SrTiO3 twin boundary and detect a change in LaAlO3/SrTiO3 interface current distribution. Our data directly confirm the existence of polarity at the twin boundaries, and demonstrate that they can serve as effective tunable gates. As the location of SrTiO3 domain walls can be controlled using external field stimuli, our findings suggest a novel approach to manipulate SrTiO3-based devices on the nanoscale.

    更新日期:2017-09-21
  • Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-18
    Ryusuke Futamura, Taku Iiyama, Yuma Takasaki, Yury Gogotsi, Mark J. Biggs, Mathieu Salanne, Julie Ségalini, Patrice Simon, Katsumi Kaneko

    Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of a widely used ionic liquid (EMI–TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can accommodate only a single layer of ions. Instead, equally charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. This finding opens the door for the design of better materials for electrochemical applications.

    更新日期:2017-09-21
  • Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO2
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-18
    Toshinari Koketsu, Jiwei Ma, Benjamin J. Morgan, Monique Body, Christophe Legein, Walid Dachraoui, Mattia Giannini, Arnaud Demortière, Mathieu Salanne, François Dardoize, Henri Groult, Olaf J. Borkiewicz, Karena W. Chapman, Peter Strasser, Damien Dambournet

    In contrast to monovalent lithium or sodium ions, the reversible insertion of multivalent ions such as Mg2+ and Al3+ into electrode materials remains an elusive goal. Here, we demonstrate a new strategy to achieve reversible Mg2+ and Al3+ insertion in anatase TiO2, achieved through aliovalent doping, to introduce a large number of titanium vacancies that act as intercalation sites. We present a broad range of experimental and theoretical characterizations that show a preferential insertion of multivalent ions into titanium vacancies, allowing a much greater capacity to be obtained compared to pure TiO2. This result highlights the possibility to use the chemistry of defects to unlock the electrochemical activity of known materials, providing a new strategy for the chemical design of materials for practical multivalent batteries.

    更新日期:2017-09-21
  • Exponential growth and selection in self-replicating materials from DNA origami rafts
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-18
    Xiaojin He, Ruojie Sha, Rebecca Zhuo, Yongli Mi, Paul M. Chaikin, Nadrian C. Seeman

    Exponential growth and selection in self-replicating materials from DNA origami raftsNature Materials, Published online: 18 September 2017; doi:10.1038/nmat4986Self-replication and exponential growth are essential in nature. Here, the authors design a system of DNA origami rafts that exponentially replicate and demonstrate sensitivity to environmental changes.

    更新日期:2017-09-21
  • Electrotunable nanoplasmonic liquid mirror
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-11
    Yunuen Montelongo, Debabrata Sikdar, Ye Ma, Alastair J. S. McIntosh, Leonora Velleman, Anthony R. Kucernak, Joshua B. Edel, Alexei A. Kornyshev

    Recently, there has been a drive to design and develop fully tunable metamaterials for applications ranging from new classes of sensors to superlenses among others. Although advances have been made, tuning and modulating the optical properties in real time remains a challenge. We report on the first realization of a reversible electrotunable liquid mirror based on voltage-controlled self-assembly/disassembly of 16 nm plasmonic nanoparticles at the interface between two immiscible electrolyte solutions. We show that optical properties such as reflectivity and spectral position of the absorption band can be varied in situ within ±0.5 V. This observed effect is in excellent agreement with theoretical calculations corresponding to the change in average interparticle spacing. This electrochemical fully tunable nanoplasmonic platform can be switched from a highly reflective ‘mirror’ to a transmissive ‘window’ and back again. This study opens a route towards realization of such platforms in future micro/nanoscale electrochemical cells, enabling the creation of tunable plasmonic metamaterials.

    更新日期:2017-09-12
  • Observation of the spin Nernst effect
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-11
    S. Meyer, Y.-T. Chen, S. Wimmer, M. Althammer, T. Wimmer, R. Schlitz, S. Geprägs, H. Huebl, D. Ködderitzsch, H. Ebert, G. E. W. Bauer, R. Gross, S. T. B. Goennenwein

    Observation of the spin Nernst effectNature Materials, Published online: 11 September 2017; doi:10.1038/nmat4964The observation of the spin Nernst effect in platinum thin film is reported. This and the spin Hall effects are found to be of similar magnitude.

    更新日期:2017-09-12
  • A map of high-mobility molecular semiconductors
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-11
    S. Fratini, S. Ciuchi, D. Mayou, G. Trambly de Laissardière, A. Troisi

    The charge mobility of molecular semiconductors is limited by the large fluctuation of intermolecular transfer integrals, often referred to as off-diagonal dynamic disorder, which causes transient localization of the carriers’ eigenstates. Using a recently developed theoretical framework, we show here that the electronic structure of the molecular crystals determines its sensitivity to intermolecular fluctuations. We build a map of the transient localization lengths of high-mobility molecular semiconductors to identify what patterns of nearest-neighbour transfer integrals in the two-dimensional (2D) high-mobility plane protect the semiconductor from the effect of dynamic disorder and yield larger mobility. Such a map helps rationalizing the transport properties of the whole family of molecular semiconductors and is also used to demonstrate why common textbook approaches fail in describing this important class of materials. These results can be used to rapidly screen many compounds and design new ones with optimal transport characteristics.

    更新日期:2017-09-12
  • Long-lived force patterns and deformation waves at repulsive epithelial boundaries
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-11
    Pilar Rodríguez-Franco, Agustí Brugués, Ariadna Marín-Llauradó, Vito Conte, Guiomar Solanas, Eduard Batlle, Jeffrey J. Fredberg, Pere Roca-Cusachs, Raimon Sunyer, Xavier Trepat

    For an organism to develop and maintain homeostasis, cell types with distinct functions must often be separated by physical boundaries. The formation and maintenance of such boundaries are commonly attributed to mechanisms restricted to the cells lining the boundary. Here we show that, besides these local subcellular mechanisms, the formation and maintenance of tissue boundaries involves long-lived, long-ranged mechanical events. Following contact between two epithelial monolayers expressing, respectively, EphB2 and its ligand ephrinB1, both monolayers exhibit oscillatory patterns of traction forces and intercellular stresses that tend to pull cell–matrix adhesions away from the boundary. With time, monolayers jam, accompanied by the emergence of deformation waves that propagate away from the boundary. This phenomenon is not specific to EphB2/ephrinB1 repulsion but is also present during the formation of boundaries with an inert interface and during fusion of homotypic epithelial layers. Our findings thus unveil a global physical mechanism that sustains tissue separation independently of the biochemical and mechanical features of the local tissue boundary.

    更新日期:2017-09-12
  • Cell mechanics: When tissues collide
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-11
    Ulrich S. Schwarz, Falko Ziebert

    Cell mechanics: When tissues collideNature Materials, Published online: 11 September 2017; doi:10.1038/nmat4988Quantitative analysis of colliding cell monolayers reveals surprising wave phenomena involving contractility, jamming and activation of epithelial cells.

    更新日期:2017-09-12
  • Organic semiconductors: A map to find winners
    Nat. Mater. (IF 39.737) Pub Date : 2017-09-11
    Jenny Nelson

    Organic semiconductors: A map to find winnersNature Materials, Published online: 11 September 2017; doi:10.1038/nmat4992High-mobility molecular crystals can be identified by considering only the sign and relative magnitude of the electronic coupling between neighbouring molecules. A map helps to explain experimental mobilities and to design promising materials.

    更新日期:2017-09-12
  • Instilling defect tolerance in new compounds
    Nat. Mater. (IF 39.737) Pub Date : 
    Aron Walsh, Alex Zunger

    The properties of semiconducting solids are determined by the imperfections they contain. Established physical phenomena can be converted into practical design principles for optimizing defects and doping in a broad range of technology-enabling materials.

    更新日期:2017-09-04
  • Integrin binding: Sticking around vessels
    Nat. Mater. (IF 39.737) Pub Date : 
    Michael R. Blatchley, Sharon Gerecht

    Integrin binding: Sticking around vessels Nature Materials, Published online: 29 August 2017; doi:10.1038/nmat4977 A study demonstrates that controlled integrin binding on a biomaterial was capable of promoting vascular cell sprouting and formation of a non-leaky blood vessel network in a healthy and diseased state.

    更新日期:2017-08-29
  • Valleytronics: Magnetization without polarization
    Nat. Mater. (IF 39.737) Pub Date : 
    Hongyi Yu, Wang Yao

    Valleytronics: Magnetization without polarization Nature Materials, Published online: 29 August 2017; doi:10.1038/nmat4979 A pure electrical generation of magnetization through electrons' valley magnetic moment has been observed in a strained two-dimensional semiconductor.

    更新日期:2017-08-29
  • Ticking all the boxes
    Nat. Mater. (IF 39.737) Pub Date : 

    Ticking all the boxes Nature Materials, Published online: 29 August 2017; doi:10.1038/nmat4985 Nature Materials is extending editorial policies regarding transparency of reported data in manuscripts from the physical and life sciences.

    更新日期:2017-08-29
  • Nanocrystal superlattices: No need to wait
    Nat. Mater. (IF 39.737) Pub Date : 
    Kun Liu, Eugenia Kumacheva

    Nanocrystal superlattices: No need to wait Nature Materials, Published online: 29 August 2017; doi:10.1038/nmat4980 In contrast with protocols reporting self-assembly of nanocrystals after synthesis, Pd nanocrystals rapidly form 3D micrometre-size superlattices during growth. The nanocrystals keep growing after assembly, tuning the size of the lattice.

    更新日期:2017-08-29
  • Ticking all the boxes
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-29

    Nature Materials is extending editorial policies regarding transparency of reported data in manuscripts from the physical and life sciences.

    更新日期:2017-08-29
  • Valleytronics: Magnetization without polarization
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-29
    Hongyi Yu, Wang Yao

    A pure electrical generation of magnetization through electrons' valley magnetic moment has been observed in a strained two-dimensional semiconductor.

    更新日期:2017-08-29
  • Microporous polymers: Ultrapermeable membranes
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-31
    Yan Yin, Michael D. Guiver

    Microporous membranes were designed from the loose packing of two-dimensional polymer chains — a breakthrough giving both ultrahigh permeability and good selectivity for gas separations.

    更新日期:2017-08-29
  • Raman spectroscopy: Enhanced by organic surfaces
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-07
    John R. Lombardi

    Nanostructured films of organic semiconductors are now shown to enhance the Raman signal of probe molecules, paving the way to the realization of substrates for Raman spectroscopy with molecular selectivity.

    更新日期:2017-08-29
  • Carbon nanotubes: Wiry matter–light coupling
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-17
    Jeremy J. Baumberg

    Electrical injection into polaritons, built from admixing excitons in carbon nanotubes with light in a surrounding microcavity, has been achieved.

    更新日期:2017-08-29
  • Nanocrystal superlattices: No need to wait
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-29
    Kun Liu, Eugenia Kumacheva

    In contrast with protocols reporting self-assembly of nanocrystals after synthesis, Pd nanocrystals rapidly form 3D micrometre-size superlattices during growth. The nanocrystals keep growing after assembly, tuning the size of the lattice.

    更新日期:2017-08-29
  • Integrin binding: Sticking around vessels
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-29
    Michael R. Blatchley, Sharon Gerecht

    A study demonstrates that controlled integrin binding on a biomaterial was capable of promoting vascular cell sprouting and formation of a non-leaky blood vessel network in a healthy and diseased state.

    更新日期:2017-08-29
  • Valley magnetoelectricity in single-layer MoS2
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-10
    Jieun Lee, Zefang Wang, Hongchao Xie, Kin Fai Mak, Jie Shan

    Valley magnetization in single-layer MoS2 is demonstrated by breaking the three-fold rotational symmetry via uniaxial stress. The results are consistent with a theoretical model of valley magnetoelectricity driven by Berry curvature effects.

    更新日期:2017-08-29
  • Modulation of thermal and thermoelectric transport in individual carbon nanotubes by fullerene encapsulation
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-31
    Takashi Kodama, Masato Ohnishi, Woosung Park, Takuma Shiga, Joonsuk Park, Takashi Shimada, Hisanori Shinohara, Junichiro Shiomi, Kenneth E. Goodson

    Encapsulation of single- and double-wall carbon nanotubes in carbon nanocages, which may contain gadolinium or erbium, leads to a reduction of the thermal conductivity and an improved Seebeck coefficient.

    更新日期:2017-08-29
  • Tunable room-temperature magnetic skyrmions in Ir/Fe/Co/Pt multilayers
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-17
    Anjan Soumyanarayanan, M. Raju, A. L. Gonzalez Oyarce, Anthony K. C. Tan, Mi-Young Im, A. P. Petrović, Pin Ho, K. H. Khoo, M. Tran, C. K. Gan, F. Ernult, C. Panagopoulos

    Magnetic skyrmions are nanoscale topological spin structures offering great promise for next-generation information storage technologies. The recent discovery of sub-100-nm room-temperature (RT) skyrmions in several multilayer films has triggered vigorous efforts to modulate their physical properties for their use in devices. Here we present a tunable RT skyrmion platform based on multilayer stacks of Ir/Fe/Co/Pt, which we study using X-ray microscopy, magnetic force microscopy and Hall transport techniques. By varying the ferromagnetic layer composition, we can tailor the magnetic interactions governing skyrmion properties, thereby tuning their thermodynamic stability parameter by an order of magnitude. The skyrmions exhibit a smooth crossover between isolated (metastable) and disordered lattice configurations across samples, while their size and density can be tuned by factors of two and ten, respectively. We thus establish a platform for investigating functional sub-50-nm RT skyrmions, pointing towards the development of skyrmion-based memory devices.

    更新日期:2017-08-29
  • A magnetic topological semimetal Sr1−yMn1−zSb2 (y, z < 0.1)
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-24
    J. Y. Liu, J. Hu, Q. Zhang, D. Graf, H. B. Cao, S. M. A. Radmanesh, D. J. Adams, Y. L. Zhu, G. F. Cheng, X. Liu, W. A. Phelan, J. Wei, M. Jaime, F. Balakirev, D. A. Tennant, J. F. DiTusa, I. Chiorescu, L. Spinu, Z. Q. Mao

    Weyl (WSMs) evolve from Dirac semimetals in the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry. The WSM phases in TaAs-class materials and photonic crystals are due to the loss of space-inversion symmetry. For TRS-breaking WSMs, despite numerous theoretical and experimental efforts, few examples have been reported. In this Article, we report a new type of magnetic semimetal Sr1−yMn1−zSb2 (y, z < 0.1) with nearly massless relativistic fermion behaviour (m∗ =  0.04 − 0.05m0, where m0 is the free-electron mass). This material exhibits a ferromagnetic order for 304 K  <  T  <  565 K, but a canted antiferromagnetic order with a ferromagnetic component for T  <  304 K. The combination of relativistic fermion behaviour and ferromagnetism in Sr1−yMn1−zSb2 offers a rare opportunity to investigate the interplay between relativistic fermions and spontaneous TRS breaking.

    更新日期:2017-08-29
  • Electrical pumping and tuning of exciton-polaritons in carbon nanotube microcavities
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-17
    Arko Graf, Martin Held, Yuriy Zakharko, Laura Tropf, Malte C. Gather, Jana Zaumseil

    Exciton-polaritons are hybrid light–matter particles that form upon strong coupling of an excitonic transition to a cavity mode. As bosons, polaritons can form condensates with coherent laser-like emission. For organic materials, optically pumped condensation was achieved at room temperature but electrically pumped condensation remains elusive due to insufficient polariton densities. Here we combine the outstanding optical and electronic properties of purified, solution-processed semiconducting (6,5) single-walled carbon nanotubes (SWCNTs) in a microcavity-integrated light-emitting field-effect transistor to realize efficient electrical pumping of exciton-polaritons at room temperature with high current densities (>10 kA cm−2) and tunability in the near-infrared (1,060 nm to 1,530 nm). We demonstrate thermalization of SWCNT polaritons, exciton-polariton pumping rates ~104 times higher than in current organic polariton devices, direct control over the coupling strength (Rabi splitting) via the applied gate voltage, and a tenfold enhancement of polaritonic over excitonic emission. This powerful material–device combination paves the way to carbon-based polariton emitters and possibly lasers.

    更新日期:2017-08-29
  • Nanostructured organic semiconductor films for molecular detection with surface-enhanced Raman spectroscopy
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-07
    Mehmet Yilmaz, Esra Babur, Mehmet Ozdemir, Rebecca L. Gieseking, Yavuz Dede, Ugur Tamer, George C. Schatz, Antonio Facchetti, Hakan Usta, Gokhan Demirel

    π-Conjugated organic semiconductors have been explored in several optoelectronic devices, yet their use in molecular detection as surface-enhanced Raman spectroscopy (SERS)-active platforms is unknown. Herein, we demonstrate that SERS-active, superhydrophobic and ivy-like nanostructured films of a molecular semiconductor, α,ω-diperfluorohexylquaterthiophene (DFH-4T), can be easily fabricated by vapour deposition. DFH-4T films without any additional plasmonic layer exhibit unprecedented Raman signal enhancements up to 3.4 × 103 for the probe molecule methylene blue. The combination of quantum mechanical computations, comparative experiments with a fluorocarbon-free α,ω-dihexylquaterthiophene (DH-4T), and thin-film microstructural analysis demonstrates the fundamental roles of the π-conjugated core fluorocarbon substitution and the unique DFH-4T film morphology governing the SERS response. Furthermore, Raman signal enhancements up to ~1010 and sub-zeptomole (<10−21 mole) analyte detection were accomplished by coating the DFH-4T films with a thin gold layer. Our results offer important guidance for the molecular design of SERS-active organic semiconductors and easily fabricable SERS platforms for ultrasensitive trace analysis.

    更新日期:2017-08-29
  • Dynamic surface self-reconstruction is the key of highly active perovskite nano-electrocatalysts for water splitting
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-17
    Emiliana Fabbri, Maarten Nachtegaal, Tobias Binninger, Xi Cheng, Bae-Jung Kim, Julien Durst, Francesco Bozza, Thomas Graule, Robin Schäublin, Luke Wiles, Morgan Pertoso, Nemanja Danilovic, Katherine E. Ayers, Thomas J. Schmidt

    The growing need to store increasing amounts of renewable energy has recently triggered substantial R&D efforts towards efficient and stable water electrolysis technologies. The oxygen evolution reaction (OER) occurring at the electrolyser anode is central to the development of a clean, reliable and emission-free hydrogen economy. The development of robust and highly active anode materials for OER is therefore a great challenge and has been the main focus of research. Among potential candidates, perovskites have emerged as promising OER electrocatalysts. In this study, by combining a scalable cutting-edge synthesis method with time-resolved X-ray absorption spectroscopy measurements, we were able to capture the dynamic local electronic and geometric structure during realistic operando conditions for highly active OER perovskite nanocatalysts. Ba0.5Sr0.5Co0.8Fe0.2O3−δ as nano-powder displays unique features that allow a dynamic self-reconstruction of the material’s surface during OER, that is, the growth of a self-assembled metal oxy(hydroxide) active layer. Therefore, besides showing outstanding performance at both the laboratory and industrial scale, we provide a fundamental understanding of the operando OER mechanism for highly active perovskite catalysts. This understanding significantly differs from design principles based on ex situ characterization techniques.

    更新日期:2017-08-29
  • Polymer ultrapermeability from the inefficient packing of 2D chains
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-31
    Ian Rose, C. Grazia Bezzu, Mariolino Carta, Bibiana Comesaña-Gándara, Elsa Lasseuguette, M. Chiara Ferrari, Paola Bernardo, Gabriele Clarizia, Alessio Fuoco, Johannes C. Jansen, Kyle E. Hart, Thilanga P. Liyana-Arachchi, Coray M. Colina, Neil B. McKeown

    The promise of ultrapermeable polymers, such as poly(trimethylsilylpropyne) (PTMSP), for reducing the size and increasing the efficiency of membranes for gas separations remains unfulfilled due to their poor selectivity. We report an ultrapermeable polymer of intrinsic microporosity (PIM-TMN-Trip) that is substantially more selective than PTMSP. From molecular simulations and experimental measurement we find that the inefficient packing of the two-dimensional (2D) chains of PIM-TMN-Trip generates a high concentration of both small (<0.7 nm) and large (0.7–1.0 nm) micropores, the former enhancing selectivity and the latter permeability. Gas permeability data for PIM-TMN-Trip surpass the 2008 Robeson upper bounds for O2/N2, H2/N2, CO2/N2, H2/CH4 and CO2/CH4, with the potential for biogas purification and carbon capture demonstrated for relevant gas mixtures. Comparisons between PIM-TMN-Trip and structurally similar polymers with three-dimensional (3D) contorted chains confirm that its additional intrinsic microporosity is generated from the awkward packing of its 2D polymer chains in a 3D amorphous solid. This strategy of shape-directed packing of chains of microporous polymers may be applied to other rigid polymers for gas separations.

    更新日期:2017-08-29
  • The processing and heterostructuring of silk with light
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-14
    Mehra S. Sidhu, Bhupesh Kumar, Kamal P. Singh

    Spider silk is a tough, elastic and lightweight biomaterial, although there is a lack of tools available for non-invasive processing of silk structures. Here we show that nonlinear multiphoton interactions of silk with few-cycle femtosecond pulses allow the processing and heterostructuring of the material in ambient air. Two qualitatively different responses, bulging by multiphoton absorption and plasma-assisted ablation, are observed for low- and high-peak intensities, respectively. Plasma ablation allows us to make localized nanocuts, microrods, nanotips and periodic patterns with minimal damage while preserving molecular structure. The bulging regime facilitates confined bending and microwelding of silk with materials such as metal, glass and Kevlar with strengths comparable to pristine silk. Moreover, analysis of Raman bands of microwelded joints reveals that the polypeptide backbone remains intact while perturbing its weak hydrogen bonds. Using this approach, we fabricate silk-based functional topological microstructures, such as Mobiüs strips, chiral helices and silk-based sensors.

    更新日期:2017-08-29
  • Revealing crystalline domains in a mollusc shell single-crystalline prism
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-10
    F. Mastropietro, P. Godard, M. Burghammer, C. Chevallard, J. Daillant, J. Duboisset, M. Allain, P. Guenoun, J. Nouet, V. Chamard

    Biomineralization integrates complex processes leading to an extraordinary diversity of calcareous biomineral crystalline architectures, in intriguing contrast with the consistent presence of a sub-micrometric granular structure. Hence, gaining access to the crystalline architecture at the mesoscale, that is, over a few granules, is key to building realistic biomineralization scenarios. Here we provide the nanoscale spatial arrangement of the crystalline structure within the ‘single-crystalline’ prisms of the prismatic layer of a Pinctada margaritifera shell, exploiting three-dimensional X-ray Bragg ptychography microscopy. We reveal the details of the mesocrystalline organization, evidencing a crystalline coherence extending over a few granules. We additionally prove the existence of larger iso-oriented crystalline domains, slightly misoriented with respect to each other, around one unique rotation axis, and whose shapes are correlated with iso-strain domains. The highlighted mesocrystalline properties support recent biomineralization models involving partial fusion of oriented nanoparticle assembly and/or liquid droplet precursors.

    更新日期:2017-08-29
  • Hydrogels with precisely controlled integrin activation dictate vascular patterning and permeability
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-07
    Shuoran Li, Lina R. Nih, Haylee Bachman, Peng Fei, Yilei Li, Eunwoo Nam, Robert Dimatteo, S. Thomas Carmichael, Thomas H. Barker, Tatiana Segura

    Integrin binding to bioengineered hydrogel scaffolds is essential for tissue regrowth and regeneration, yet not all integrin binding can lead to tissue repair. Here, we show that through engineering hydrogel materials to promote α3/α5β1 integrin binding, we can promote the formation of a space-filling and mature vasculature compared with hydrogel materials that promote αvβ3 integrin binding. In vitro, α3/α5β1 scaffolds promoted endothelial cells to sprout and branch, forming organized extensive networks that eventually reached and anastomosed with neighbouring branches. In vivo, α3/α5β1 scaffolds delivering vascular endothelial growth factor (VEGF) promoted non-tortuous blood vessel formation and non-leaky blood vessels by 10 days post-stroke. In contrast, materials that promote αvβ3 integrin binding promoted endothelial sprout clumping in vitro and leaky vessels in vivo. This work shows that precisely controlled integrin activation from a biomaterial can be harnessed to direct therapeutic vessel regeneration and reduce VEGF-induced vascular permeability in vivo.

    更新日期:2017-08-29
  • Mott transition by an impulsive dielectric breakdown
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-21
    H. Yamakawa, T. Miyamoto, T. Morimoto, T. Terashige, H. Yada, N. Kida, M. Suda, H. M. Yamamoto, R. Kato, K. Miyagawa, K. Kanoda, H. Okamoto

    Mott transition by an impulsive dielectric breakdown Nature Materials, Published online: 21 August 2017; doi:10.1038/nmat4967 Irradiation with a strong terahertz electric-field pulse is found to induce a Mott transition in an organic molecular compound. The metallization is attributed to an impulsive dielectric breakdown.

    更新日期:2017-08-24
  • Nanodiffusion in electrocatalytic films
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-21
    Cyrille Costentin, Carlo Di Giovanni, Marion Giraud, Jean-Michel Savéant, Cédric Tard

    In the active interest aroused by electrochemical reactions’ catalysis, related to modern energy challenges, films deposited on electrodes are often preferred to homogeneous catalysts. A particularly promising variety of such films, in terms of efficiency and selectivity, is offered by sprinkling catalytic nanoparticles onto a conductive network. Coupled with the catalytic reaction, the competitive occurrence of various modes of substrate diffusion—diffusion toward nanoparticles (‘nanodiffusion’) against film linear diffusion and solution linear diffusion—is analysed theoretically. It is governed by a dimensionless parameter that contains all the experimental factors, thus allowing one to single out the conditions in which nanodiffusion is the dominant mode of mass transport. These theoretical predictions are illustrated experimentally by proton reduction on a mixture of platinum nanoparticles and carbon dispersed in a Nafion film deposited on a glassy carbon electrode. The density of nanoparticles and the scan rate are used as experimental variables to test the theory.

    更新日期:2017-08-24
  • Violation of Ohm’s law in a Weyl metal
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-14
    Dongwoo Shin, Yongwoo Lee, M. Sasaki, Yoon Hee Jeong, Franziska Weickert, Jon B. Betts, Heon-Jung Kim, Ki-Seok Kim, Jeehoon Kim

    Violation of Ohm’s law in a Weyl metal Nature Materials, Published online: 14 August 2017; doi:10.1038/nmat4965 The chiral anomaly in the Weyl metal phase is reported to lead to a breakdown of Ohm’s law.

    更新日期:2017-08-19
  • The processing and heterostructuring of silk with light
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-14
    Mehra S. Sidhu, Bhupesh Kumar, Kamal P. Singh

    Spider silk is a tough, elastic and lightweight biomaterial, although there is a lack of tools available for non-invasive processing of silk structures. Here we show that nonlinear multiphoton interactions of silk with few-cycle femtosecond pulses allow the processing and heterostructuring of the material in ambient air. Two qualitatively different responses, bulging by multiphoton absorption and plasma-assisted ablation, are observed for low- and high-peak intensities, respectively. Plasma ablation allows us to make localized nanocuts, microrods, nanotips and periodic patterns with minimal damage while preserving molecular structure. The bulging regime facilitates confined bending and microwelding of silk with materials such as metal, glass and Kevlar with strengths comparable to pristine silk. Moreover, analysis of Raman bands of microwelded joints reveals that the polypeptide backbone remains intact while perturbing its weak hydrogen bonds. Using this approach, we fabricate silk-based functional topological microstructures, such as Mobiüs strips, chiral helices and silk-based sensors.

    更新日期:2017-08-19
  • Flexible shape-memory scaffold for minimally invasive delivery of functional tissues
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-14
    Miles Montgomery, Samad Ahadian, Locke Davenport Huyer, Mauro Lo Rito, Robert A. Civitarese, Rachel D. Vanderlaan, Jun Wu, Lewis A. Reis, Abdul Momen, Saeed Akbari, Aric Pahnke, Ren-Ke Li, Christopher A. Caldarone, Milica Radisic

    Despite great progress in engineering functional tissues for organ repair, including the heart, an invasive surgical approach is still required for their implantation. Here, we designed an elastic and microfabricated scaffold using a biodegradable polymer (poly(octamethylene maleate (anhydride) citrate)) for functional tissue delivery via injection. The scaffold’s shape memory was due to the microfabricated lattice design. Scaffolds and cardiac patches (1 cm × 1 cm) were delivered through an orifice as small as 1 mm, recovering their initial shape following injection without affecting cardiomyocyte viability and function. In a subcutaneous syngeneic rat model, injection of cardiac patches was equivalent to open surgery when comparing vascularization, macrophage recruitment and cell survival. The patches significantly improved cardiac function following myocardial infarction in a rat, compared with the untreated controls. Successful minimally invasive delivery of human cell-derived patches to the epicardium, aorta and liver in a large-animal (porcine) model was achieved.

    更新日期:2017-08-19
  • Bronze-mean hexagonal quasicrystal
    Nat. Mater. (IF 39.737) Pub Date : 2017-08-14
    Tomonari Dotera, Shinichi Bekku, Primož Ziherl

    Bronze-mean hexagonal quasicrystal Nature Materials, Published online: 14 August 2017; doi:10.1038/nmat4963 A two-dimensional quasicrystalline tiling based on the bronze-mean hexagonal pattern is proposed.

    更新日期:2017-08-19
  • Oxide superlattices: Balancing polar vortices and stripes
    Nat. Mater. (IF 39.737) Pub Date : 
    Matthew Dawber

    A tuned oxide superlattice possesses two coexisting phases — one ferroelectric, the other with vortex order — which can be interconverted under electric field, changing material properties.

    更新日期:2017-08-13
  • Raman spectroscopy: Enhanced by organic surfaces
    Nat. Mater. (IF 39.737) Pub Date : 
    John R. Lombardi

    Nanostructured films of organic semiconductors are now shown to enhance the Raman signal of probe molecules, paving the way to the realization of substrates for Raman spectroscopy with molecular selectivity.

    更新日期:2017-08-13
  • Measurement of the spin temperature of optically cooled nuclei and GaAs hyperfine constants in GaAs/AlGaAs quantum dots
    Nat. Mater. (IF 39.737) Pub Date : 
    E. A. Chekhovich, A. Ulhaq, E. Zallo, F. Ding, O. G. Schmidt, M. S. Skolnick

    Measurement of the nuclear polarization in GaAs/AlGaAs quantum dots through manipulation of the nuclear spin states with radiofrequency pulses reveals polarizations up to 80%.

    更新日期:2017-08-13
  • Phase coexistence and electric-field control of toroidal order in oxide superlattices
    Nat. Mater. (IF 39.737) Pub Date : 
    A. R. Damodaran, J. D. Clarkson, Z. Hong, H. Liu, A. K. Yadav, C. T. Nelson, S.-L. Hsu, M. R. McCarter, K.-D. Park, V. Kravtsov, A. Farhan, Y. Dong, Z. Cai, H. Zhou, P. Aguado-Puente, P. García-Fernández, J. Íñiguez, J. Junquera, A. Scholl, M. B. Raschke, L.-Q. Chen, D. D. Fong, R. Ramesh, L. W. Martin

    Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO3/SrTiO3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a1/a2 phase. At room temperature, the coexisting vortex and ferroelectric phases form a mesoscale, fibre-textured hierarchical superstructure. The vortex phase possesses an axial polarization, set by the net polarization of the surrounding ferroelectric domains, such that it possesses a multi-order-parameter state and belongs to a class of gyrotropic electrotoroidal compounds. Finally, application of electric fields to this mixed-phase system permits interconversion between the vortex and the ferroelectric phases concomitant with order-of-magnitude changes in piezoelectric and nonlinear optical responses. Our findings suggest new cross-coupled functionalities.

    更新日期:2017-08-13
  • Hydrogels with precisely controlled integrin activation dictate vascular patterning and permeability
    Nat. Mater. (IF 39.737) Pub Date : 
    Shuoran Li, Lina R. Nih, Haylee Bachman, Peng Fei, Yilei Li, Eunwoo Nam, Robert Dimatteo, S. Thomas Carmichael, Thomas H. Barker, Tatiana Segura

    Integrin binding to bioengineered hydrogel scaffolds is essential for tissue regrowth and regeneration, yet not all integrin binding can lead to tissue repair. Here, we show that through engineering hydrogel materials to promote α3/α5β1 integrin binding, we can promote the formation of a space-filling and mature vasculature compared with hydrogel materials that promote αvβ3 integrin binding. In vitro, α3/α5β1 scaffolds promoted endothelial cells to sprout and branch, forming organized extensive networks that eventually reached and anastomosed with neighbouring branches. In vivo, α3/α5β1 scaffolds delivering vascular endothelial growth factor (VEGF) promoted non-tortuous blood vessel formation and non-leaky blood vessels by 10 days post-stroke. In contrast, materials that promote αvβ3 integrin binding promoted endothelial sprout clumping in vitro and leaky vessels in vivo. This work shows that precisely controlled integrin activation from a biomaterial can be harnessed to direct therapeutic vessel regeneration and reduce VEGF-induced vascular permeability in vivo.

    更新日期:2017-08-13
  • Nanostructured organic semiconductor films for molecular detection with surface-enhanced Raman spectroscopy
    Nat. Mater. (IF 39.737) Pub Date : 
    Mehmet Yilmaz, Esra Babur, Mehmet Ozdemir, Rebecca L. Gieseking, Yavuz Dede, Ugur Tamer, George C. Schatz, Antonio Facchetti, Hakan Usta, Gokhan Demirel

    π-Conjugated organic semiconductors have been explored in several optoelectronic devices, yet their use in molecular detection as surface-enhanced Raman spectroscopy (SERS)-active platforms is unknown. Herein, we demonstrate that SERS-active, superhydrophobic and ivy-like nanostructured films of a molecular semiconductor, α,ω-diperfluorohexylquaterthiophene (DFH-4T), can be easily fabricated by vapour deposition. DFH-4T films without any additional plasmonic layer exhibit unprecedented Raman signal enhancements up to 3.4 × 103 for the probe molecule methylene blue. The combination of quantum mechanical computations, comparative experiments with a fluorocarbon-free α,ω-dihexylquaterthiophene (DH-4T), and thin-film microstructural analysis demonstrates the fundamental roles of the π-conjugated core fluorocarbon substitution and the unique DFH-4T film morphology governing the SERS response. Furthermore, Raman signal enhancements up to ~1010 and sub-zeptomole (<10−21 mole) analyte detection were accomplished by coating the DFH-4T films with a thin gold layer. Our results offer important guidance for the molecular design of SERS-active organic semiconductors and easily fabricable SERS platforms for ultrasensitive trace analysis.

    更新日期:2017-08-13
  • En Marche!
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-26

    Researchers and their institutions must play their full part in ensuring that the exciting changes now sweeping France succeed.

    更新日期:2017-08-12
  • Thermal hall effect: Turn your phonon
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-26
    Xavier Moya, Neil D. Mathur

    Heat travelling down a thermal gradient has been found to undergo a significant deflection by a magnetic field in a multiferroic insulator.

    更新日期:2017-08-12
  • Acoustic metamaterials: Living bandgaps
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-26
    Kyle J. M. Bishop

    Sound waves drive the organization of particle scatterers into stable structures, exhibiting phononic band gaps that heal from disturbances and adapt to changes in the drive.

    更新日期:2017-08-12
  • Maraging steels: Making steel strong and cheap
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-26
    J. W. Morris Jr

    Introducing high-density ordered nanoprecipitates into martensitic steel increases strength at modest cost.

    更新日期:2017-08-12
  • Strength of the repulsive part of the interatomic potential determines fragility in metallic liquids
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-10
    Christopher E. Pueblo, Minhua Sun, K. F. Kelton

    Liquid fragility is a basic characteristic of glasses and there is debate as to what controls it. X-ray scattering of several metallic liquids now suggests that the strength of the repulsive part of the interatomic potential is key.

    更新日期:2017-08-12
  • Biological labels: Here comes the spaser
    Nat. Mater. (IF 39.737) Pub Date : 2017-07-26
    Catherine Alix-Panabières, Klaus Pantel

    Plasmonic nanolasers embedded in living cells and animal tissues are shown to emit strongly, making them promising potential biocompatible probes.

    更新日期:2017-08-12
  • Giant thermal Hall effect in multiferroics
    Nat. Mater. (IF 39.737) Pub Date : 2017-05-15
    T. Ideue, T. Kurumaji, S. Ishiwata, Y. Tokura

    Giant coupling between magnetism and phonons — or the giant thermal Hall effect — is reported in the insulating polar magnet (ZnxFe1−x)2Mo3O8.

    更新日期:2017-08-12
  • Multi-stimuli manipulation of antiferromagnetic domains assessed by second-harmonic imaging
    Nat. Mater. (IF 39.737) Pub Date : 2017-05-08
    J.-Y. Chauleau, E. Haltz, C. Carrétéro, S. Fusil, M. Viret

    Sub-coercive electric fields and sub-picosecond light pulses are shown to enable low-power manipulation of antiferromagnetic domains in the multiferroic BiFeO3.

    更新日期:2017-08-12
  • Emergence of an enslaved phononic bandgap in a non-equilibrium pseudo-crystal
    Nat. Mater. (IF 39.737) Pub Date : 2017-06-19
    Nicolas Bachelard, Chad Ropp, Marc Dubois, Rongkuo Zhao, Yuan Wang, Xiang Zhang

    Material systems that reside far from thermodynamic equilibrium have the potential to exhibit dynamic properties and behaviours resembling those of living organisms. Here we realize a non-equilibrium material characterized by a bandgap whose edge is enslaved to the wavelength of an external coherent drive. The structure dynamically self-assembles into an unconventional pseudo-crystal geometry that equally distributes momentum across elements. The emergent bandgap is bestowed with lifelike properties, such as the ability to self-heal to perturbations and adapt to sudden changes in the drive. We derive an exact analytical solution for both the spatial organization and the bandgap features, revealing the mechanism for enslavement. This work presents a framework for conceiving lifelike non-equilibrium materials and emphasizes the potential for the dynamic imprinting of material properties through external degrees of freedom.

    更新日期:2017-08-12
  • Synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 by noble metal substitution reaction in Ti3SiC2 for high-temperature-stable Ohmic contacts to SiC
    Nat. Mater. (IF 39.737) Pub Date : 2017-05-01
    Hossein Fashandi, Martin Dahlqvist, Jun Lu, Justinas Palisaitis, Sergei I. Simak, Igor A. Abrikosov, Johanna Rosen, Lars Hultman, Mike Andersson, Anita Lloyd Spetz, Per Eklund

    The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti3AuC2 and Ti3Au2C2 phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti3SiC2 single-crystal thin films with simultaneous out-diffusion of Si. Ti3IrC2 is subsequently produced by a substitution reaction of Ir for Au in Ti3Au2C2. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 °C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.

    更新日期:2017-08-12
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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