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  • Amorphous topological insulators constructed from random point sets
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-15
    Noah P. Mitchell, Lisa M. Nash, Daniel Hexner, Ari M. Turner, William T. M. Irvine

    The discovery that the band structure of electronic insulators may be topologically non-trivial has revealed distinct phases of electronic matter with novel properties1,2. Recently, mechanical lattices have been found to have similarly rich structure in their phononic excitations3,4, giving rise to protected unidirectional edge modes5,6,7. In all of these cases, however, as well as in other topological metamaterials3,8, the underlying structure was finely tuned, be it through periodicity, quasi-periodicity or isostaticity. Here we show that amorphous Chern insulators can be readily constructed from arbitrary underlying structures, including hyperuniform, jammed, quasi-crystalline and uniformly random point sets. While our findings apply to mechanical and electronic systems alike, we focus on networks of interacting gyroscopes as a model system. Local decorations control the topology of the vibrational spectrum, endowing amorphous structures with protected edge modes—with a chirality of choice. Using a real-space generalization of the Chern number, we investigate the topology of our structures numerically, analytically and experimentally. The robustness of our approach enables the topological design and self-assembly of non-crystalline topological metamaterials on the micro and macro scale.

    更新日期:2018-01-15
  • Superconductivity in few-layer stanene
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-15
    Menghan Liao, Yunyi Zang, Zhaoyong Guan, Haiwei Li, Yan Gong, Kejing Zhu, Xiao-Peng Hu, Ding Zhang, Yong Xu, Ya-Yu Wang, Ke He, Xu-Cun Ma, Shou-Cheng Zhang, Qi-Kun Xue

    A single atomic slice of α-tin—stanene—has been predicted to host the quantum spin Hall effect at room temperature, offering an ideal platform to study low-dimensional and topological physics. Although recent research has focused on monolayer stanene, the quantum size effect in few-layer stanene could profoundly change material properties, but remains unexplored. By exploring the layer degree of freedom, we discover superconductivity in few-layer stanene down to a bilayer grown on PbTe, while bulk α-tin is not superconductive. Through substrate engineering, we further realize a transition from a single-band to a two-band superconductor with a doubling of the transition temperature. In situ angle-resolved photoemission spectroscopy (ARPES) together with first-principles calculations elucidate the corresponding band structure. The theory also indicates the existence of a topologically non-trivial band. Our experimental findings open up novel strategies for constructing two-dimensional topological superconductors.

    更新日期:2018-01-15
  • Destabilizing turbulence in pipe flow
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-08
    Jakob Kühnen, Baofang Song, Davide Scarselli, Nazmi Burak Budanur, Michael Riedl, Ashley P. Willis, Marc Avila, Björn Hof

    Turbulence is the major cause of friction losses in transport processes and it is responsible for a drastic drag increase in flows over bounding surfaces. While much effort is invested into developing ways to control and reduce turbulence intensities1,2,3, so far no methods exist to altogether eliminate turbulence if velocities are sufficiently large. We demonstrate for pipe flow that appropriate distortions to the velocity profile lead to a complete collapse of turbulence and subsequently friction losses are reduced by as much as 90%. Counterintuitively, the return to laminar motion is accomplished by initially increasing turbulence intensities or by transiently amplifying wall shear. Since neither the Reynolds number nor the shear stresses decrease (the latter often increase), these measures are not indicative of turbulence collapse. Instead, an amplification mechanism4,5 measuring the interaction between eddies and the mean shear is found to set a threshold below which turbulence is suppressed beyond recovery.

    更新日期:2018-01-08
  • Peace in the pipeline
    Nat. Phys. (IF 22.806) Pub Date : 
    Mitul Luhar

    Peace in the pipeline Peace in the pipeline, Published online: 08 January 2018; doi:10.1038/s41567-017-0037-0 Turbulence in pipe flows causes substantial friction and economic losses. The solution to appease the flow through pipelines might be, counterintuitively, to initially enhance turbulent mixing and get laminar flow in return.

    更新日期:2018-01-08
  • Threes company
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-08
    Benjamin J. Wieder

    Threes company Threes company, Published online: 08 January 2018; doi:10.1038/s41567-017-0032-5 Enabled by recent advances in symmetry and electronic structure, researchers have observed signatures of unconventional threefold degeneracies in tungsten carbide, challenging a longstanding paradigm in nodal semimetals.

    更新日期:2018-01-08
  • Three-component fermions with surface Fermi arcs in tungsten carbide
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-08
    J.-Z. Ma, J.-B. He, Y.-F. Xu, B. Q. Lv, D. Chen, W.-L. Zhu, S. Zhang, L.-Y. Kong, X. Gao, L.-Y. Rong, Y.-B. Huang, P. Richard, C.-Y. Xi, E. S. Choi, Y. Shao, Y.-L. Wang, H.-J. Gao, X. Dai, C. Fang, H.-M. Weng, G.-F. Chen, T. Qian, H. Ding

    Topological Dirac and Weyl semimetals not only host quasiparticles analogous to the elementary fermionic particles in high-energy physics, but also have a non-trivial band topology manifested by gapless surface states, which induce exotic surface Fermi arcs1,2. Recent advances suggest new types of topological semimetal, in which spatial symmetries protect gapless electronic excitations without high-energy analogues3,4,5,6,7,8,9,10,11. Here, using angle-resolved photoemission spectroscopy, we observe triply degenerate nodal points near the Fermi level of tungsten carbide with space group P6̄m2 P 6 ̄ m 2 (no. 187), in which the low-energy quasiparticles are described as three-component fermions distinct from Dirac and Weyl fermions. We further observe topological surface states, whose constant-energy contours constitute pairs of ‘Fermi arcs’ connecting to the surface projections of the triply degenerate nodal points, proving the non-trivial topology of the newly identified semimetal state.

    更新日期:2018-01-08
  • Non-Hermitian physics and PT symmetry
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Ramy El-Ganainy, Konstantinos G. Makris, Mercedeh Khajavikhan, Ziad H. Musslimani, Stefan Rotter, Demetrios N. Christodoulides

    In recent years, notions drawn from non-Hermitian physics and parity–time (PT) symmetry have attracted considerable attention. In particular, the realization that the interplay between gain and loss can lead to entirely new and unexpected features has initiated an intense research effort to explore non-Hermitian systems both theoretically and experimentally. Here we review recent progress in this emerging field, and provide an outlook to future directions and developments.

    更新日期:2018-01-05
  • Economic complexity: From useless to keystone
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    César A. Hidalgo

    Economic complexity: From useless to keystoneEconomic complexity: From useless to keystone, Published online: 05 January 2018; doi:10.1038/nphys4337Technological innovation seems to be dominated by chance. But a new mathematical analysis suggests we might be able to anticipate when seemingly useless technologies become keystones of more complex environments.

    更新日期:2018-01-05
  • Geophysics: Lightning-fast tremors
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Federico Levi

    Geophysics: Lightning-fast tremorsGeophysics: Lightning-fast tremors, Published online: 05 January 2018; doi:10.1038/nphys4341Geophysics: Lightning-fast tremors

    更新日期:2018-01-05
  • Quantum teleportation, onwards and upwards
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Anton Zeilinger

    Quantum teleportation, onwards and upwardsQuantum teleportation, onwards and upwards, Published online: 05 January 2018; doi:10.1038/nphys4339As we move beyond the twentieth anniversary of the teleportation of a quantum state, it's clear that the coming years will be just as fruitful.

    更新日期:2018-01-05
  • Evolutionary game theory: Metric of cooperation
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Andrea Taroni

    Evolutionary game theory: Metric of cooperationEvolutionary game theory: Metric of cooperation, Published online: 05 January 2018; doi:10.1038/nphys4343Evolutionary game theory: Metric of cooperation

    更新日期:2018-01-05
  • Leading lights
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Mark Buchanan

    Leading lightsLeading lights, Published online: 05 January 2018; doi:10.1038/nphys4345Leading lights

    更新日期:2018-01-05
  • Twisting neutrons may reveal their internal structure
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Hugo Larocque, Ido Kaminer, Vincenzo Grillo, Robert W. Boyd, Ebrahim Karimi

    Twisting neutrons may reveal their internal structureTwisting neutrons may reveal their internal structure, Published online: 05 January 2018; doi:10.1038/nphys4322Twisting neutrons may reveal their internal structure

    更新日期:2018-01-05
  • The IceCube chronicles
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-05
    Leonie Mueck

    The IceCube chroniclesThe IceCube chronicles, Published online: 05 January 2018; doi:10.1038/nphys4326The IceCube chronicles

    更新日期:2018-01-05
  • Don’t close the gates
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-01
    Samuel V. Scarpino

    Don’t close the gatesDon’t close the gates, Published online: 01 January 2018; doi:10.1038/s41567-017-0028-1It seems obvious that restricting travel should help prevent the surge of epidemics. But a new mathematical analysis now demonstrates that mobility often reduces the heterogeneity in population distributions, thereby lowering the epidemic risk.

    更新日期:2018-01-01
  • Self-hybridization within non-Hermitian localized plasmonic systems
    Nat. Phys. (IF 22.806) Pub Date : 2018-01-01
    Hugo Lourenço-Martins, Pabitra Das, Luiz H. G. Tizei, Raphaël Weil, Mathieu Kociak

    The orthogonal eigenmodes are well-defined solutions of Hermitian equations describing many physical situations from quantum mechanics to acoustics. However, a large variety of non-Hermitian problems, including gravitational waves close to black holes or leaky electromagnetic cavities, require the use of a bi-orthogonal eigenbasis with consequences challenging our physical understanding1,2,3,4. The need to compensate for energy losses made the few successful attempts5,6,7,8 to experimentally probe non-Hermiticity extremely complicated. We overcome this problem by considering localized plasmonic systems. As the non-Hermiticity in these systems does not stem from temporal invariance breaking but from spatial symmetry breaking, its consequences can be observed more easily. We report on the theoretical and experimental evidence for non-Hermiticity-induced strong coupling between surface plasmon modes of different orders within silver nanodaggers. The symmetry conditions for triggering this counter-intuitive self-hybridization phenomenon are provided. Similar observable effects are expected to exist in any system exhibiting bi-orthogonal eigenmodes.

    更新日期:2018-01-01
  • Observation of dynamical vortices after quenches in a system with topology
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-18
    N. Fläschner, D. Vogel, M. Tarnowski, B. S. Rem, D.-S. Lühmann, M. Heyl, J. C. Budich, L. Mathey, K. Sengstock, C. Weitenberg

    Topological phases constitute an exotic form of matter characterized by non-local properties rather than local order parameters1. The paradigmatic Haldane model on a hexagonal lattice features such topological phases distinguished by an integer topological invariant known as the first Chern number2. Recently, the identification of non-equilibrium signatures of topology in the dynamics of such systems has attracted particular attention3,4,5,6. Here, we experimentally study the dynamical evolution of the wavefunction using time- and momentum-resolved full state tomography for spin-polarized fermionic atoms in driven optical lattices7. We observe the appearance, movement and annihilation of dynamical vortices in momentum space after sudden quenches close to the topological phase transition. These dynamical vortices can be interpreted as dynamical Fisher zeros of the Loschmidt amplitude8, which signal a so-called dynamical phase transition9,10. Our results pave the way to a deeper understanding of the connection between topological phases and non-equilibrium dynamics.

    更新日期:2017-12-18
  • Coherent inflationary dynamics for Bose–Einstein condensates crossing a quantum critical point
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-18
    Lei Feng, Logan W. Clark, Anita Gaj, Cheng Chin

    Quantum phase transitions, transitions between many-body ground states, are of extensive interest in research ranging from condensed-matter physics to cosmology1,2,3,4. Key features of the phase transitions include a stage with rapidly growing new order, called inflation in cosmology5, followed by the formation of topological defects6,7,8. How inflation is initiated and evolves into topological defects remains a hot topic of debate. Ultracold atomic gas offers a pristine and tunable platform to investigate quantum critical dynamics9,10,11,12,13,14,15,16,17,18,19,20,21. We report the observation of coherent inflationary dynamics across a quantum critical point in driven Bose–Einstein condensates. The inflation manifests in the exponential growth of density waves and populations in well-resolved momentum states. After the inflation stage, extended coherent dynamics is evident in both real and momentum space. We present an intuitive description of the quantum critical dynamics in our system and demonstrate the essential role of phase fluctuations in the formation of topological defects.

    更新日期:2017-12-18
  • Critical regimes driven by recurrent mobility patterns of reaction–diffusion processes in networks
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-18
    J. Gómez-Gardeñes, D. Soriano-Paños, A. Arenas

    Reaction–diffusion processes1 have been widely used to study dynamical processes in epidemics2,3,4 and ecology5 in networked metapopulations. In the context of epidemics6, reaction processes are understood as contagions within each subpopulation (patch), while diffusion represents the mobility of individuals between patches. Recently, the characteristics of human mobility7, such as its recurrent nature, have been proven crucial to understand the phase transition to endemic epidemic states8,9. Here, by developing a framework able to cope with the elementary epidemic processes, the spatial distribution of populations and the commuting mobility patterns, we discover three different critical regimes of the epidemic incidence as a function of these parameters. Interestingly, we reveal a regime of the reaction–diffussion process in which, counter-intuitively, mobility is detrimental to the spread of disease. We analytically determine the precise conditions for the emergence of any of the three possible critical regimes in real and synthetic networks.

    更新日期:2017-12-18
  • Frustration and thermalization in an artificial magnetic quasicrystal
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-11
    Dong Shi, Zoe Budrikis, Aaron Stein, Sophie A. Morley, Peter D. Olmsted, Gavin Burnell, Christopher H. Marrows

    Artificial frustrated systems offer a playground to study the emergent properties of interacting systems. Most work to date has been on spatially periodic systems, known as artificial spin ices when the interacting elements are magnetic. Here we have studied artificial magnetic quasicrystals based on quasiperiodic Penrose tiling patterns of interacting nanomagnets. We construct a low-energy configuration from a step-by-step approach that we propose as a ground state. Topologically induced emergent frustration means that this configuration cannot be constructed from vertices in their ground states. It has two parts, a quasi-one-dimensional ‘skeleton’ that spans the entire pattern and is capable of long-range order, surrounding ‘flippable’ clusters of macrospins that lead to macroscopic degeneracy. Magnetic force microscopy imaging of Penrose tiling arrays revealed superdomains that are larger for more strongly coupled arrays, especially after annealing the array above its blocking temperature.

    更新日期:2017-12-11
  • Signatures of a dissipative phase transition in photon correlation measurements
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-11
    Thomas Fink, Anne Schade, Sven Höfling, Christian Schneider, Ataç Imamoglu

    Understanding and characterizing phase transitions in driven-dissipative systems constitutes a new frontier for many-body physics1,2,3,4,5,6,7,8. A generic feature of dissipative phase transitions is a vanishing gap in the Liouvillian spectrum9, which leads to long-lived deviations from the steady state as the system is driven towards the transition. Here, we show that photon correlation measurements can be used to characterize the corresponding critical slowing down of non-equilibrium dynamics. We focus on the extensively studied phenomenon of optical bistability in GaAs cavity polaritons10,11, which can be described as a first-order dissipative phase transition12,13,14. Increasing the excitation strength towards the bistable range results in an increasing photon-bunching signal along with a decay time that is prolonged by more than nine orders of magnitude as compared with that of single polaritons. In the limit of strong polariton interactions leading to pronounced quantum fluctuations, the mean-field bistability threshold is washed out. Nevertheless, the functional form with which the Liouvillian gap closes as the thermodynamic limit is approached provides a signature of the emerging dissipative phase transition. Our results establish photon correlation measurements as an invaluable tool for studying dynamical properties of dissipative phase transitions without requiring phase-sensitive interferometric measurements.

    更新日期:2017-12-11
  • Quantum criticality among entangled spin chains
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-11
    N. Blanc, J. Trinh, L. Dong, X. Bai, A. A. Aczel, M. Mourigal, L. Balents, T. Siegrist, A. P. Ramirez

    An important challenge in magnetism is the unambiguous identification of a quantum spin liquid1,2, of potential importance for quantum computing. In such a material, the magnetic spins should be fluctuating in the quantum regime, instead of frozen in a classical long-range-ordered state. While this requirement dictates systems3,4 wherein classical order is suppressed by a frustrating lattice5, an ideal system would allow tuning of quantum fluctuations by an external parameter. Conventional three-dimensional antiferromagnets can be tuned through a quantum critical point—a region of highly fluctuating spins—by an applied magnetic field. Such systems suffer from a weak specific-heat peak at the quantum critical point, with little entropy available for quantum fluctuations6. Here we study a different type of antiferromagnet, comprised of weakly coupled antiferromagnetic spin-1/2 chains as realized in the molecular salt K2PbCu(NO2)6. Across the temperature–magnetic field boundary between three-dimensional order and the paramagnetic phase, the specific heat exhibits a large peak whose magnitude approaches a value suggestive of the spinon Sommerfeld coefficient of isolated quantum spin chains. These results demonstrate an alternative approach for producing quantum matter via a magnetic-field-induced shift of entropy from one-dimensional short-range order to a three-dimensional quantum critical point.

    更新日期:2017-12-11
  • Quantum violation of an instrumental test
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-11
    Rafael Chaves, Gonzalo Carvacho, Iris Agresti, Valerio Di Giulio, Leandro Aolita, Sandro Giacomini, Fabio Sciarrino

    Inferring causal relations from experimental observations is of primal importance in science. Instrumental tests provide an essential tool for that aim, as they allow one to estimate causal dependencies even in the presence of unobserved common causes. In view of Bell’s theorem, which implies that quantum mechanics is incompatible with our most basic notions of causality, it is of utmost importance to understand whether and how paradigmatic causal tools obtained in a classical setting can be carried over to the quantum realm. Here we show that quantum effects imply radically different predictions in the instrumental scenario. Among other results, we show that an instrumental test can be violated by entangled quantum states. Furthermore, we demonstrate such violation using a photonic set-up with active feed-forward of information, thus providing an experimental proof of this new form of non-classical behaviour. Our findings have fundamental implications in causal inference and may also lead to new applications of quantum technologies.

    更新日期:2017-12-11
  • Erratum: Structural and quantum-state phase transitions in van der Waals layered materials
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    Heejun Yang, Sung Wng Kim, Manish Chhowalla, Young Hee Lee

    Erratum: Structural and quantum-state phase transitions in van der Waals layered materials Erratum: Structural and quantum-state phase transitions in van der Waals layered materials, Published online: 05 December 2017; doi:10.1038/nphys4315 Erratum: Structural and quantum-state phase transitions in van der Waals layered materials

    更新日期:2017-12-05
  • A matter of time
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    Helen Margolis

    A matter of time A matter of time, Published online: 05 December 2017; doi:10.1038/nphys4327 The arrival of a new type of timekeeper heralds the end of the second as we know it, as Helen Margolis explains.

    更新日期:2017-12-05
  • Energy transitions
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    Mark Buchanan

    Energy transitions Energy transitions, Published online: 05 December 2017; doi:10.1038/nphys4329 Energy transitions

    更新日期:2017-12-05
  • Condensed-matter physics: Weyl metamaterials
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    David Abergel

    Condensed-matter physics: Weyl metamaterials Condensed-matter physics: Weyl metamaterials, Published online: 05 December 2017; doi:10.1038/nphys4333 Condensed-matter physics: Weyl metamaterials

    更新日期:2017-12-05
  • Quantum spin liquids: To be or not to be
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    Yun Li

    Quantum spin liquids: To be or not to be Quantum spin liquids: To be or not to be, Published online: 05 December 2017; doi:10.1038/nphys4335 Quantum spin liquids: To be or not to be

    更新日期:2017-12-05
  • Portraits of physicists
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    Marco Bentivenga, Richard Brierley, Nina Meinzer

    Portraits of physicists Portraits of physicists, Published online: 05 December 2017; doi:10.1038/nphys4324 Portraits of physicists

    更新日期:2017-12-05
  • Heisenberg's uncertain legacy
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05

    Heisenberg's uncertain legacy Heisenberg's uncertain legacy, Published online: 05 December 2017; doi:10.1038/nphys4330 Heisenberg's uncertain legacy

    更新日期:2017-12-05
  • Erratum: Structural and quantum-state phase transitions in van der Waals layered materials
    Nat. Phys. (IF 22.806) Pub Date : 2017-12-05
    Heejun Yang, Sung Wng Kim, Manish Chhowalla, Young Hee Lee

    Erratum: Structural and quantum-state phase transitions in van der Waals layered materials Erratum: Structural and quantum-state phase transitions in van der Waals layered materials, Published online: 05 December 2017; doi:10.1038/nphys4328 Erratum: Structural and quantum-state phase transitions in van der Waals layered materials

    更新日期:2017-12-05
  • Statistical projection effects in a hydrodynamic pilot-wave system
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-27
    Pedro J. Sáenz, Tudor Cristea-Platon, John W. M. Bush

    Millimetric liquid droplets can walk across the surface of a vibrating fluid bath, self-propelled through a resonant interaction with their own guiding or ‘pilot’ wave fields. These walking droplets, or ‘walkers’, exhibit several features previously thought to be peculiar to the microscopic, quantum realm. In particular, walkers confined to circular corrals manifest a wave-like statistical behaviour reminiscent of that of electrons in quantum corrals. Here we demonstrate that localized topological inhomogeneities in an elliptical corral may lead to resonant projection effects in the walker’s statistics similar to those reported in quantum corrals. Specifically, we show that a submerged circular well may drive the walker to excite specific eigenmodes in the bath that result in drastic changes in the particle’s statistical behaviour. The well tends to attract the walker, leading to a local peak in the walker’s position histogram. By placing the well at one of the foci, a mode with maxima near the foci is preferentially excited, leading to a projection effect in the walker’s position histogram towards the empty focus, an effect strongly reminiscent of the quantum mirage. Finally, we demonstrate that the mean pilot-wave field has the same form as the histogram describing the walker’s statistics.

    更新日期:2017-11-28
  • Diffraction and microscopy with attosecond electron pulse trains
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-27
    Yuya Morimoto, Peter Baum

    Attosecond spectroscopy1,2,3,4,5,6,7 can resolve electronic processes directly in time, but a movie-like space–time recording is impeded by the too long wavelength (~100 times larger than atomic distances) or the source–sample entanglement in re-collision techniques8,9,10,11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons1,2,3,4,5,6,7 or re-colliding wavepackets8,9,10,11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a < 10-as delay of Bragg emission and demonstrates the possibility of analytic attosecond–ångström diffraction. Real-space electron microscopy visualizes with sub-light-cycle resolution how an optical wave propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space–time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

    更新日期:2017-11-28
  • Space-saving tips to lower stress
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-27
    Vernita D. Gordon

    Space-saving tips to lower stress Space-saving tips to lower stress, Published online: 27 November 2017; doi:10.1038/s41567-017-0012-9 Understanding how some single cells evolved into multicellular life means figuring out how they overcome the stresses associated with crowding as they multiply. New insights from yeast suggest that changes in the shape of cells may provide an answer.

    更新日期:2017-11-28
  • Quantum physics dropwise
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-27
    Tomas Bohr

    Quantum physics dropwise Quantum physics dropwise, Published online: 27 November 2017; doi:10.1038/s41567-017-0015-6 Classical wave-driven particles can mimic basic quantum properties, but how far this parallel extends is yet to be seen. Evidence for quantum-like mirages in a system of droplets moving on a fluid surface pushes the analogy into many-body territory.

    更新日期:2017-11-28
  • Cellular packing, mechanical stress and the evolution of multicellularity
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-27
    Shane Jacobeen, Jennifer T. Pentz, Elyes C. Graba, Colin G. Brandys, William C. Ratcliff, Peter J. Yunker

    The evolution of multicellularity set the stage for sustained increases in organismal complexity1,2,3,4,5. However, a fundamental aspect of this transition remains largely unknown: how do simple clusters of cells evolve increased size when confronted by forces capable of breaking intracellular bonds? Here we show that multicellular snowflake yeast clusters6,7,8 fracture due to crowding-induced mechanical stress. Over seven weeks (~291 generations) of daily selection for large size, snowflake clusters evolve to increase their radius 1.7-fold by reducing the accumulation of internal stress. During this period, cells within the clusters evolve to be more elongated, concomitant with a decrease in the cellular volume fraction of the clusters. The associated increase in free space reduces the internal stress caused by cellular growth, thus delaying fracture and increasing cluster size. This work demonstrates how readily natural selection finds simple, physical solutions to spatial constraints that limit the evolution of group size—a fundamental step in the evolution of multicellularity.

    更新日期:2017-11-28
  • Superradiance of an ensemble of nuclei excited by a free electron laser
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-20
    Aleksandr I. Chumakov, Alfred Q. R. Baron, Ilya Sergueev, Cornelius Strohm, Olaf Leupold, Yuri Shvyd’ko, Gennadi V. Smirnov, Rudolf Rüffer, Yuichi Inubushi, Makina Yabashi, Kensuke Tono, Togo Kudo, Tetsuya Ishikawa

    In 1954 Dicke predicted the accelerated initial decay of multiple atomic excitations1, laying the foundation for the concept of superradiance. Further studies2,3,4 suggested that emission of the total energy was similarly accelerated, provided that the system reaches the inversion threshold. Superradiant emission of the total energy has been confirmed by numerous studies4,5,6,7,8,9,10,11,12, yet the acceleration of the initial decay has not been experimentally demonstrated. Here we use resonant diffraction of X-rays from the Mössbauer transition13 of 57Fe nuclei to investigate superradiant decay, photon by photon, along the entire chain of the de-excitation cascade of up to 68 simultaneous coherent nuclear excitations created by a pulse of an X-ray free-electron laser. We find agreement with Dicke’s theory1 for the accelerated initial decay as the number of excitations is increased. We also find that our results are in agreement with a simple statistical model, providing a necessary baseline for discussing further properties of superradiance, within and beyond the low-excitation regime.

    更新日期:2017-11-21
  • Topologically protected refraction of robust kink states in valley photonic crystals
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-13
    Fei Gao, Haoran Xue, Zhaoju Yang, Kueifu Lai, Yang Yu, Xiao Lin, Yidong Chong, Gennady Shvets, Baile Zhang

    Topologically protected refraction of robust kink states in valley photonic crystals Topologically protected refraction of robust kink states in valley photonic crystals, Published online: 13 November 2017; doi:10.1038/nphys4304 NatureArticleSnippet(type=short-summary, markup= A photonic crystal can realize an analogue of a valley Hall insulator, promising more flexibility than in condensed-matter systems to explore these exotic topological states. , isJats=true)

    更新日期:2017-11-13
  • How drops start sliding over solid surfaces
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-06
    Nan Gao, Florian Geyer, Dominik W. Pilat, Sanghyuk Wooh, Doris Vollmer, Hans-Jürgen Butt, Rüdiger Berger

    How drops start sliding over solid surfaces How drops start sliding over solid surfaces, Published online: 06 November 2017; doi:10.1038/nphys4305 NatureArticleSnippet(type=short-summary, markup= A liquid droplet is shown to slide across a solid surface subject to friction forces analogous with those between two solids. The phenomenon is generic, and closes a gap in our understanding of liquid–solid friction. , isJats=true)

    更新日期:2017-11-06
  • Phase ordering of charge density waves traced by ultrafast low-energy electron diffraction
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-06
    S. Vogelgesang, G. Storeck, J. G. Horstmann, T. Diekmann, M. Sivis, S. Schramm, K. Rossnagel, S. Schäfer, C. Ropers

    Phase ordering of charge density waves traced by ultrafast low-energy electron diffraction Phase ordering of charge density waves traced by ultrafast low-energy electron diffraction, Published online: 06 November 2017; doi:10.1038/nphys4309 NatureArticleSnippet(type=short-summary, markup= A tracing of the phase-ordering kinetics of a charge density wave system demonstrates the potential of ultrafast low-energy electron diffraction for studying phase transitions and ordering phenomena at surfaces and in low-dimensional systems. , isJats=true)

    更新日期:2017-11-06
  • Unconventional mass enhancement around the Dirac nodal loop in ZrSiS
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-06
    S. Pezzini, M. R. van Delft, L. M. Schoop, B. V. Lotsch, A. Carrington, M. I. Katsnelson, N. E. Hussey, S. Wiedmann

    The topological properties of fermions arise from their low-energy Dirac-like band dispersion and associated chirality. Initially confined to points, extensions of the Dirac dispersion to lines, and even loops, have now been uncovered, and semimetals hosting such features have been identified. However, experimental evidence for the enhanced correlation effects predicted to occur in these topological semimetals has been lacking. Here, we report a quantum oscillation study of the nodal-loop semimetal ZrSiS in high magnetic fields that reveals significant enhancement in the effective mass of the quasiparticles residing near the nodal loop. Above a threshold field, magnetic breakdown occurs across gaps in the loop structure with orbits that enclose different windings around its vertices, each winding accompanied by an additional π Berry phase. The amplitudes of these breakdown orbits exhibit an anomalous temperature dependence. These findings demonstrate the emergence of novel, correlation-driven physics in ZrSiS associated with the Dirac-like quasiparticles.

    更新日期:2017-11-06
  • Soft matter: Sticky fingers
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02
    Federico Levi

    Soft matter: Sticky fingers Soft matter: Sticky fingers, Published online: 02 November 2017; doi:10.1038/nphys4313

    更新日期:2017-11-02
  • Many-body localization: Going long
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02
    Andrea Taroni

    Many-body localization: Going long Many-body localization: Going long, Published online: 02 November 2017; doi:10.1038/nphys4317

    更新日期:2017-11-02
  • Ripples in spacetime
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02

    Ripples in spacetime Ripples in spacetime, Published online: 02 November 2017; doi:10.1038/nphys4321 NatureArticleSnippet(type=standfirst, markup= The 2017 Nobel prize in Physics has been awarded to Rainer Weiss, Barry C. Barish and Kip S. Thorne “for decisive contributions to the LIGO detector and the observation of gravitational waves”. , isJats=true)

    更新日期:2017-11-02
  • Quantum anomalous hall effect: Honeycomb recipe
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02
    Luke Fleet

    Quantum anomalous hall effect: Honeycomb recipe Quantum anomalous hall effect: Honeycomb recipe, Published online: 02 November 2017; doi:10.1038/nphys4319

    更新日期:2017-11-02
  • Celebrate the scientific hierarchy
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02
    George Ellis, David Sloan

    Celebrate the scientific hierarchy Celebrate the scientific hierarchy, Published online: 02 November 2017; doi:10.1038/nphys4300 NatureArticleSnippet(type=standfirst, markup= The validity of our scientific descriptions of reality does not hinge on their emergence from a more fundamental theory. , isJats=true)

    更新日期:2017-11-02
  • When lost in a multiverse
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02
    Andre Geim

    When lost in a multiverse When lost in a multiverse, Published online: 02 November 2017; doi:10.1038/nphys4310 NatureArticleSnippet(type=standfirst, markup= Wonder material graphene makes metrology practical and relaxed, says Andre Geim . , isJats=true)

    更新日期:2017-11-02
  • Gas detection: Sensor extraordinaire
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-02
    Andreas H. Trabesinger

    Gas detection: Sensor extraordinaire Gas detection: Sensor extraordinaire, Published online: 02 November 2017; doi:10.1038/nphys4316

    更新日期:2017-11-02
  • Biomechanics: Split sites
    Nat. Phys. (IF 22.806) Pub Date : 2017-11-01
    Abigail Klopper

    Biomechanics: Split sites Biomechanics: Split sites, Published online: 02 November 2017; doi:10.1038/nphys4320

    更新日期:2017-11-02
  • Quantum imaging with incoherently scattered light from a free-electron laser
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-30
    Raimund Schneider, Thomas Mehringer, Giuseppe Mercurio, Lukas Wenthaus, Anton Classen, Günter Brenner, Oleg Gorobtsov, Adrian Benz, Daniel Bhatti, Lars Bocklage, Birgit Fischer, Sergey Lazarev, Yuri Obukhov, Kai Schlage, Petr Skopintsev, Jochen Wagner, Felix Waldmann, Svenja Willing, Ivan Zaluzhnyy, Wilfried Wurth, Ivan A. Vartanyants, Ralf Röhlsberger, Joachim von Zanthier

    Quantum imaging with incoherently scattered light from a free-electron laser Nature Physics, Published online: 30 October 2017; doi:10.1038/nphys4301 The intensity correlations in incoherently scattered X-rays from a free-electron laser can be exploited to image 2D objects with a resolution close to or below the diffraction limit.

    更新日期:2017-10-30
  • Anomalous dispersion of microcavity trion-polaritons
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-30
    S. Dhara, C. Chakraborty, K. M. Goodfellow, L. Qiu, T. A. O’Loughlin, G. W. Wicks, Subhro Bhattacharjee, A. N. Vamivakas

    Anomalous dispersion of microcavity trion-polaritons Nature Physics, Published online: 30 October 2017; doi:10.1038/nphys4303 A study of the strong coupling of different exciton species in two-dimensional molybdenum diselenide in a cavity uncovers the rich many-body physics and may lead to new devices.

    更新日期:2017-10-30
  • The physics of quantum materials
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-30
    B. Keimer, J. E. Moore

    The physical description of all materials is rooted in quantum mechanics, which describes how atoms bond and electrons interact at a fundamental level. Although these quantum effects can in many cases be approximated by a classical description at the macroscopic level, in recent years there has been growing interest in material systems where quantum effects remain manifest over a wider range of energy and length scales. Such quantum materials include superconductors, graphene, topological insulators, Weyl semimetals, quantum spin liquids, and spin ices. Many of them derive their properties from reduced dimensionality, in particular from confinement of electrons to two-dimensional sheets. Moreover, they tend to be materials in which electrons cannot be considered as independent particles but interact strongly and give rise to collective excitations known as quasiparticles. In all cases, however, quantum-mechanical effects fundamentally alter properties of the material. This Review surveys the electronic properties of quantum materials through the prism of the electron wavefunction, and examines how its entanglement and topology give rise to a rich variety of quantum states and phases; these are less classically describable than conventional ordered states also driven by quantum mechanics, such as ferromagnetism.

    更新日期:2017-10-30
  • A scientist walks into a bar
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-23
    Nina Meinzer

    A scientist walks into a bar Nature Physics, Published online: 23 October 2017; doi:10.1038/nphys4307

    更新日期:2017-10-30
  • Fermi surface in the absence of a Fermi liquid in the Kondo insulator SmB6
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-23
    M. Hartstein, W. H. Toews, Y.-T. Hsu, B. Zeng, X. Chen, M. Ciomaga Hatnean, Q. R. Zhang, S. Nakamura, A. S. Padgett, G. Rodway-Gant, J. Berk, M. K. Kingston, G. H. Zhang, M. K. Chan, S. Yamashita, T. Sakakibara, Y. Takano, J.-H. Park, L. Balicas, N. Harrison, N. Shitsevalova, G. Balakrishnan, G. G. Lonzarich, R. W. Hill, M. Sutherland, Suchitra E. Sebastian

    Fermi surface in the absence of a Fermi liquid in the Kondo insulator SmB6 Nature Physics, Published online: 23 October 2017; doi:10.1038/nphys4295 Experimental study of the Kondo insulator SmB6 provides an alternative route to realize a Fermi surface in the absence of a conventional Fermi liquid.

    更新日期:2017-10-30
  • Quantum gas microscopy of an attractive Fermi–Hubbard system
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-23
    Debayan Mitra, Peter T. Brown, Elmer Guardado-Sanchez, Stanimir S. Kondov, Trithep Devakul, David A. Huse, Peter Schauß, Waseem S. Bakr

    Quantum gas microscopy of an attractive Fermi–Hubbard system Nature Physics, Published online: 23 October 2017; doi:10.1038/nphys4297 The simplest lattice model that allows the investigation of superconductivity with attractive interactions is realized using ultracold quantum gas. The experimental observation provides a lower bound on the strength of s-wave pairing correlations.

    更新日期:2017-10-30
  • Sign reversal of the order parameter in (Li1−xFex)OHFe1−yZnySe
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-23
    Zengyi Du, Xiong Yang, Dustin Altenfeld, Qiangqiang Gu, Huan Yang, Ilya Eremin, Peter J. Hirschfeld, Igor I. Mazin, Hai Lin, Xiyu Zhu, Hai-Hu Wen

    Sign reversal of the order parameter in (Li1−xFex)OHFe1−yZnySe Nature Physics, Published online: 23 October 2017; doi:10.1038/nphys4299 A scanning tunnelling microscopy study of an intercalated iron selenide-based superconductor reveals a sign change in its superconducting gap function, providing indirect evidence for the origin of the pairing mechanism in this system.

    更新日期:2017-10-30
  • Curvature-induced defect unbinding and dynamics in active nematic toroids
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-23
    Perry W. Ellis, Daniel J. G. Pearce, Ya-Wen Chang, Guillermo Goldsztein, Luca Giomi, Alberto Fernandez-Nieves

    Curvature-induced defect unbinding and dynamics in active nematic toroids Nature Physics, Published online: 23 October 2017; doi:10.1038/nphys4276 Topological defects in a turbulent active nematic on a toroidal surface are shown to segregate in regions of opposite curvature. Simulations suggest that this behaviour may be controlled — or even suppressed — by tuning the level of activity.

    更新日期:2017-10-30
  • Experimentally probing topological order and its breakdown through modular matrices
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-16
    Zhihuang Luo, Jun Li, Zhaokai Li, Ling-Yan Hung, Yidun Wan, Xinhua Peng, Jiangfeng Du

    Experimentally probing topological order and its breakdown through modular matrices Nature Physics, Published online: 16 October 2017; doi:10.1038/nphys4281 Fundamental fingerprints of topological orders may be characterized uniquely and purely by experimental means. Here the authors provide a proof of principle demonstration using interferometric measurement in a two-dimensional lattice system.

    更新日期:2017-10-30
  • Symmetry breaking by quantum coherence in single electron attachment
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-16
    E. Krishnakumar, Vaibhav S. Prabhudesai, Nigel J. Mason

    Symmetry breaking by quantum coherence in single electron attachment Nature Physics, Published online: 16 October 2017; doi:10.1038/nphys4289 Resonant electron attachment and subsequent dissociation of diatomic molecules is shown to exhibit spatial asymmetry as a consequence of coherent excitation and subsequent interference between reaction pathways.

    更新日期:2017-10-30
  • Molecular physics: Breaking up is hard to do
    Nat. Phys. (IF 22.806) Pub Date : 2017-10-16
    Daniel S. Slaughter, Thomas N. Rescigno

    Molecular physics: Breaking up is hard to do Nature Physics, Published online: 16 October 2017; doi:10.1038/nphys4308 Dissociating hydrogen gas seems like it should be as easy as pulling apart two identical atoms. But resonant electron-impact experiments reveal that quantum interference induces a fundamental asymmetry in the process.

    更新日期:2017-10-30
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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