Physics

  • Article
    | Open Access

    Berghoff et al. discover that polycrystalline MAPbI3 undergoes transient Wannier Stark localization at moderate field strengths, exhibiting substantial optical modulation with a fast response time. Since the polycrystallinity does not hinder the switching behaviour, this low-cost material is promising for light modulation and photonic applications.

    • Daniel Berghoff
    • , Johannes Bühler
    •  & Heejae Kim
  • Article
    | Open Access

    Social convention change due to diffusion is often described by agent-based models focusing on the role of social coordination. In this work the authors uncover two additional individual-level mechanisms, trend-seeking and inertia, that can critically shape the collective behavior of the population.

    • Mengbin Ye
    • , Lorenzo Zino
    •  & Ming Cao
  • Article
    | Open Access

    Three-dimensional topological insulators have become a research focal point on topological quantum matter. Here, the authors propose the non-Hermitian analogue, the exceptional topological insulator, with anomalous surface states only existing within the topological bulk embedding.

    • M. Michael Denner
    • , Anastasiia Skurativska
    •  & Titus Neupert
  • Article
    | Open Access

    CPT violation could manifest itself in annihilating positronium events, but searching for this effect would require to know the spin of the annihilating system. Here, the authors do this using a positron-emission tomography scanner, finding no violation with a statistical precision of 10−4.

    • P. Moskal
    • , A. Gajos
    •  & W. Wiślicki
  • Article
    | Open Access

    Whereas transitions from solid- to fluid-like states in systems of active particles have received much attention, the characterization of phase transitions in active fluids with self-organized vortices so far has remained elusive. James et al. take us on a numerical tour de force from active turbulence to active vortex crystals.

    • Martin James
    • , Dominik Anton Suchla
    •  & Michael Wilczek
  • Article
    | Open Access

    Twisted van der Waals systems are known to host flat electronic bands, originating from moire potential. Here, the authors predict from purely geometric considerations a new type of nearly dispersionless bands in twisted bilayer MoS2, resulting from destructive interference between effective lattice hopping matrix elements.

    • Lede Xian
    • , Martin Claassen
    •  & Angel Rubio
  • Article
    | Open Access

    Naturally occurring hyperbolic polaritons exist in a class of layered materials. Here, the authors show evidence, via optical spectroscopy, of hyperbolic exciton-polaritons in phosphorene, originating from its in-plane anisotropy and strong exciton resonances.

    • Fanjie Wang
    • , Chong Wang
    •  & Hugen Yan
  • Article
    | Open Access

    Systems of interacting oscillatory units show various types of dynamics, from uniform low-dimensional motion to high-dimensional disorder. The authors follow the path from synchronous to turbulent state via variety of complex patterns that split and collide, explaining mechanisms of their formation.

    • Sindre W. Haugland
    • , Anton Tosolini
    •  & Katharina Krischer
  • Article
    | Open Access

    Higher order synchronization in optomechanical devices is relatively unexplored. Here the authors use nonlinear parametric effects to entrain an optomechanical oscillator with a drive signal several octaves away from the oscillation frequency, and demonstrate RF frequency division.

    • Caique C. Rodrigues
    • , Cauê M. Kersul
    •  & Gustavo S. Wiederhecker
  • Article
    | Open Access

    Laser performance is constrained by various factors. Here, the authors show theoretically that the linewidth can be reduced below the standard quantum limit by engineering the output coupling of a laser to reduce noise, and discuss the potential practical implementation of this approach.

    • Chenxu Liu
    • , Maria Mucci
    •  & David Pekker
  • Article
    | Open Access

    Merons and Skyrmions, two topological spin-textures, have attracted a lot of interests due to their potential use in information storage. Here, the authors demonstrate the transformation of Meron pairs into Skyrmions without an applied magnetic field within domain walls of GdFeCo films.

    • Zhuolin Li
    • , Jian Su
    •  & Baogen Shen
  • Article
    | Open Access

    Characterizing an unknown, complex system, like an accelerator, in multi-dimensional space is a challenging task. Here the authors report a Bayesian active learning method - Constrained Proximal Bayesian Exploration - for the characterization of a complex, constrained measurement as a function of multiple free parameters.

    • Ryan Roussel
    • , Juan Pablo Gonzalez-Aguilera
    •  & Auralee Edelen
  • Article
    | Open Access

    It was predicted that lattice reconstruction can lead to the emergence of multiple ultra-flat electronic bands in twisted bilayer transition metal dichalcogenides. Here, by using scanning tunneling microscopy and spectroscopy, the authors demonstrate such bands in twisted bilayer WSe2.

    • En Li
    • , Jin-Xin Hu
    •  & Nian Lin
  • Article
    | Open Access

    The quantum anomalous Hall effect has so far been limited to temperature of the order of 20 mK. Here, Fijalkowski et al. report the existence of chiral edge channels up to the Curie temperature of bulk ferromagnetism of the magnetic topological insulator with a multi-terminal Corbino geometry.

    • Kajetan M. Fijalkowski
    • , Nan Liu
    •  & Laurens W. Molenkamp
  • Article
    | Open Access

    Point defects compromise the electronic performance of hybrid perovskites, yet no experimental identifications have been reported. Here, the authors, for the first time, identify lead monovacancy defect in MAPbI3 using positron annihilation lifetime spectroscopy with the aid of density functional theory.

    • David J. Keeble
    • , Julia Wiktor
    •  & Werner Egger
  • Article
    | Open Access

    Semiconductor microcavities allow engineering of artificial lattices with optical write-in and read-out of information. Here, the authors show an optically imprinted system of exciton-polaritons arranged in a Lieb lattice and reveal a nonequilibrium transition from scattered- to trapped polariton condensates.

    • S. Alyatkin
    • , H. Sigurdsson
    •  & P. G. Lagoudakis
  • Article
    | Open Access

    Nonreciprocal devices are crucial in scientific research and practical applications at all frequencies. Here the authors demonstrate an integrated terahertz optical isolator based on the magneto-optical effect in a nonreciprocal resonator.

    • Shixing Yuan
    • , Liao Chen
    •  & Xinliang Zhang
  • Article
    | Open Access

    The honeycomb lattice with a spin-orbit interaction can give rise to exotic quantum states. With the measurements of bulk properties and inelastic neutron scattering, Lin et al demonstrate the existence of a field induced spin-disordered state in Na2Co2TeO6 and extend the Kitaev model to 3d system.

    • Gaoting Lin
    • , Jaehong Jeong
    •  & Jie Ma
  • Article
    | Open Access

    Cherenkov detectors are used to detect high energy particles and their performance capabilities depend heavily on the material used. Here, the authors propose use of a Brewster-optics-based angular filter for a detector with increased sensitivity and particle identification capability.

    • Xiao Lin
    • , Hao Hu
    •  & Yu Luo
  • Article
    | Open Access

    Graphene nanoribbons are potential systems for engineering topological phases of matter, but the pre-required gapped phases are difficult to find. Here, the authors show that chiral graphene nanoribbons undergo a transition from metallic to topological insulators, and then to trivial band insulators as they are narrowed down to nanometer widths.

    • Jingcheng Li
    • , Sofia Sanz
    •  & Jose Ignacio Pascual
  • Article
    | Open Access

    The awareness of rock shape dependence in rockfall hazard assessment is growing, but experimental and field studies are scarce. This study presents a large data set of induced single block rockfall events quantifying the influence of rock shape and mass on its complex kinematic behaviour.

    • Andrin Caviezel
    • , Adrian Ringenbach
    •  & Perry Bartelt
  • Article
    | Open Access

    Resistive switching usually occurs by the formation of conducting filaments in the direction of current flow. Here the authors study an intriguing type of volatile metal-to-insulator resistive switching in (La,Sr)MnO3, which occurs by the formation of an insulating barrier perpendicular to the current.

    • Pavel Salev
    • , Lorenzo Fratino
    •  & Ivan K. Schuller
  • Article
    | Open Access

    Here, the authors report on evidence of an excitonic species formed by electrons in high-energy conduction band states with a negative effective mass, explaining previous observations of quantum interference phenomena in two-dimensional semiconductors.

    • Kai-Qiang Lin
    • , Chin Shen Ong
    •  & John M. Lupton
  • Article
    | Open Access

    Valley anisotropy is proposed theoretically to benefit the electrical transport of thermoelectric materials but it lacks experimental demonstration. Here, the authors demonstrate how to utilize the single anisotropic Fermi pocket in p-type Mg3Sb2 to enhance its thermoelectric properties.

    • Airan Li
    • , Chaoliang Hu
    •  & Tiejun Zhu
  • Article
    | Open Access

    Magic-angle twisted bilayer graphene exhibits a quantum anomalous Hall effect at 3/4 filling; however, its mechanism is debated. Here, the authors show that such a phase can be realized in a lattice model of twisted bilayer graphene in the strong coupling limit, and interpret the results in terms of a topological Mott insulator phase.

    • Bin-Bin Chen
    • , Yuan Da Liao
    •  & Zi Yang Meng
  • Article
    | Open Access

    Strong light-matter coupling has been realized at the level of single atoms and photons throughout most of the electromagnetic spectrum, except for the THz range. Here, the authors report a THz-scale transport gap, induced by vacuum fluctuations in carbon nanotube quantum dot through the deep strong coupling of a single electron to a THz resonator.

    • F. Valmorra
    • , K. Yoshida
    •  & T. Kontos
  • Article
    | Open Access

    Several hydrides have been observed high-Tc superconductivity under pressure, but a physical-chemical understanding of the properties enhancing Tc is still lacking. Here, the authors propose a magnitude named as networking value, combined with hydrogen fraction and the contribution of hydrogen to the density of states at Fermi level, can predict Tc of all hydrogen-based compounds with an accuracy of about 60 K.

    • Francesco Belli
    • , Trinidad Novoa
    •  & Ion Errea
  • Article
    | Open Access

    Transition metal kagome compounds have been shown to host flat bands in their bulk electronic spectrum. Here, using planar tunnelling spectroscopy supported by first-principles calculations, the authors report the signature of a novel type of flat band at the surface of antiferromagnetic kagome metal FeSn.

    • Minyong Han
    • , Hisashi Inoue
    •  & Joseph G. Checkelsky
  • Article
    | Open Access

    The development of fast and dynamic topological photonic platforms is an ongoing challenge. Here, the authors demonstrate a reprogrammable plasmonic topological insulator in which ultrafast electric switches allow for nanosecond-level switching time between different configurations.

    • Jian Wei You
    • , Qian Ma
    •  & Tie Jun Cui
  • Article
    | Open Access

    Optical excitation of transition metal dichalcogenide monolayers mostly generates excitons species with inherently short lifetime and spin/valley relaxation time. Here, the authors demonstrate efficient spin/valley optical pumping of resident electrons in n-doped WSe2 and WS2 monolayers.

    • Cedric Robert
    • , Sangjun Park
    •  & Xavier Marie
  • Article
    | Open Access

    Ultrafast diffraction is fundamental in capturing the structural dynamics of molecules. Here, the authors establish a variant of quantum state tomography for arbitrary degrees of freedom to characterize the molecular quantum states, which will enable the reconstruction of a quantum molecular movie from diffraction data.

    • Ming Zhang
    • , Shuqiao Zhang
    •  & Zheng Li
  • Article
    | Open Access

    Superconductivity in FeSe attracted great interests to understand the mechanism of high temperature superconductivity. Here, the authors report a pressure induced superconductivity with a highest Tc of ~9 K in MnSe.

    • T. L. Hung
    • , C. H. Huang
    •  & T. K. Lee
  • Article
    | Open Access

    Atomic monolayers of large-gap quantum spin Hall insulators are challenging to synthesize. Here, the authors realize massive Dirac fermions emerging from Bloch wave-function interference on a triangular lattice and achieve topologically non-trivial domains with unprecedented spatial extension.

    • Maximilian Bauernfeind
    • , Jonas Erhardt
    •  & Giorgio Sangiovanni
  • Article
    | Open Access

    Though non-Hermitian physics has contributed toward the advance of research in quantum, electronic and classical systems, previous work focused on zero- or one-dimensional systems. Here, the authors report higher-order non-Hermitian skin effects in a 2D acoustic higher-order topological insulator.

    • Xiujuan Zhang
    • , Yuan Tian
    •  & Yan-Feng Chen
  • Article
    | Open Access

    Room-temperature exciton polaritons in a monolayer WS2 are shown to display strong motional narrowing of the linewidth and enhanced first-order coherence. They can propagate for tens of micrometers while maintaining partial coherence, and display signatures of ballistic (dissipationless) transport.

    • M. Wurdack
    • , E. Estrecho
    •  & E. A. Ostrovskaya
  • Article
    | Open Access

    Toroidal moments arise from vortex like spin arrangements. These moments can then interact, giving rise to ferri- or ferro-toroidal order, though controlling such order is difficult. Here, the authors demonstrate a ferri-toroidal state in BaCoSiO4, which under an applied magnetic field exhibits multiple toroidal and metamagnetic transitions.

    • Lei Ding
    • , Xianghan Xu
    •  & Huibo Cao
  • Article
    | Open Access

    Van der Waals structures provide a new platform to explore novel physics of superconductor/ferromagnet interfaces. Here, NbSe2 Josephson junction with Cr2Ge2Te6 enables non-trivial Josephson phase by spin-dependent interaction, boosting the study of superconducting states with spin-orbit coupling and phase-controlled quantum electronic device.

    • H. Idzuchi
    • , F. Pientka
    •  & P. Kim
  • Article
    | Open Access

    Anisotropic spin S >1/2 quantum magnets can have multiple low energy modes. In this manuscript, the authors study the interaction of such low energy modes in the S = 1 antiferromagnet Ba2FeSi2O7 by combining neutron scattering measurements with an SU(3) generalization of the 1/S expansion.

    • Seung-Hwan Do
    • , Hao Zhang
    •  & Andrew D. Christianson
  • Article
    | Open Access

    Conventional quantum particles can break up into fractionalized excitations under the right conditions; however, their direct experimental observation is challenging. Here, the authors predict strong optical conductivity signatures of such excitations in the vicinity of a topological phase transition.

    • Yan-Cheng Wang
    • , Meng Cheng
    •  & Zi Yang Meng
  • Article
    | Open Access

    Previous work has shown that helical domain walls can form between states of different spin-polarization during a ferromagnetic spin transition in the fractional quantum Hall regime. Here, the authors study the transport through a single helical domain wall and find strong deviations from a simplified theory of weakly interacting edge channels.

    • Ying Wang
    • , Vadim Ponomarenko
    •  & Leonid P. Rokhinson
  • Article
    | Open Access

    Skyrmions are topological two-dimensional spin textures that in three-dimensional systems resemble strings or tubes. Here, using transmission electron microscopy Zheng et al observe the braiding of skyrmion strings in FeGe and predict this phenomenon for a large family of magnets.

    • Fengshan Zheng
    • , Filipp N. Rybakov
    •  & Rafal E. Dunin-Borkowski
  • Article
    | Open Access

    Phase transition brings a plethora of exotic phenomena and intriguing effects such as spin and charge frustration. However, the phase transition order is not always explicit. Here, the authors discover phase transition frustration near a tricritical composition point in ferroelectric Pb(Zr,Ti)O3.

    • Xian-Kui Wei
    • , Sergei Prokhorenko
    •  & Zuo-Guang Ye
  • Article
    | Open Access

    The nonequilibrium regime provides an exciting frontier in the search for novel quantum phases of matter. Here, the authors show that optically driving a lightly-doped semiconductor can lead to the spontaneous formation of a dynamical quantum liquid crystalline phase with a rotating magnetization.

    • Iliya Esin
    • , Gaurav Kumar Gupta
    •  & Netanel H. Lindner
  • Article
    | Open Access

    Mn3Sn is an anti-ferromagnetic material which displays a large magneto-optical Kerr effect, despite lacking a ferromagnetic moment. Here, the authors show that likewise, Mn3Sn, also presents a particularly large magneto-optical Voigt signal, with a negligible change in the quench time over a wide temperature range.

    • H. C. Zhao
    • , H. Xia
    •  & H. B. Zhao
  • Article
    | Open Access

    Quantized response has so far eluded classical system beyond linear response theory. Here, the authors predict that a quantized classical response, arising from fundamental mathematical properties of the Green’s function, shows up in steady-state response of a non-Hermitian system without invoking a linear response theory.

    • Linhu Li
    • , Sen Mu
    •  & Jiangbin Gong