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Article
 Open AccessMagnetooptical spectroscopy on Weyl nodes for anomalous and topological Hall effects in chiral MnGe
Previous work has proposed that the anomalous and topological Hall effects, associated with Weyl nodes, should have a signature in optical conductivity. Here, using THz optical spectroscopy, the authors assign these two effects to optical conductivity resonances, arising near band anticrossings, in thin films of MnGe.
 Y. Hayashi
 , Y. Okamura
 & Y. Takahashi

Article
 Open AccessDynamical symmetry indicators for Floquet crystals
A general theory for Floquet topology applicable to all crystalline symmetry groups is lacking. Here, the authors propose such a theory for noninteracting Floquet crystals and predict an inversionprotected Floquet higherorder topological phase with anomalous chiral hinge modes.
 Jiabin Yu
 , RuiXing Zhang
 & ZhiDa Song

Article
 Open AccessExceptional topological insulators
Threedimensional topological insulators have become a research focal point on topological quantum matter. Here, the authors propose the nonHermitian 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 AccessQuantum anomalous Hall edge channels survive up to the Curie temperature
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 multiterminal Corbino geometry.
 Kajetan M. Fijalkowski
 , Nan Liu
 & Laurens W. Molenkamp

Article
 Open AccessTopological phase transition in chiral graphene nanoribbons: from edge bands to end states
Graphene nanoribbons are potential systems for engineering topological phases of matter, but the prerequired 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 AccessRealization of topological Mott insulator in a twisted bilayer graphene lattice model
Magicangle 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.
 BinBin Chen
 , Yuan Da Liao
 & Zi Yang Meng

Article
 Open AccessEvidence of twodimensional flat band at the surface of antiferromagnetic kagome metal FeSn
Transition metal kagome compounds have been shown to host flat bands in their bulk electronic spectrum. Here, using planar tunnelling spectroscopy supported by firstprinciples 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 AccessDesign and realization of topological Dirac fermions on a triangular lattice
Atomic monolayers of largegap quantum spin Hall insulators are challenging to synthesize. Here, the authors realize massive Dirac fermions emerging from Bloch wavefunction interference on a triangular lattice and achieve topologically nontrivial domains with unprecedented spatial extension.
 Maximilian Bauernfeind
 , Jonas Erhardt
 & Giorgio Sangiovanni

Article
 Open AccessObservation of higherorder nonHermitian skin effect
Though nonHermitian physics has contributed toward the advance of research in quantum, electronic and classical systems, previous work focused on zero or onedimensional systems. Here, the authors report higherorder nonHermitian skin effects in a 2D acoustic higherorder topological insulator.
 Xiujuan Zhang
 , Yuan Tian
 & YanFeng Chen

Article
 Open AccessFractionalized conductivity and emergent selfduality near topological phase transitions
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.
 YanCheng Wang
 , Meng Cheng
 & Zi Yang Meng

Article
 Open AccessQuantized classical response from spectral winding topology
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 steadystate response of a nonHermitian system without invoking a linear response theory.
 Linhu Li
 , Sen Mu
 & Jiangbin Gong

Article
 Open AccessRealspace observations of 60nm skyrmion dynamics in an insulating magnet under low heat flow
Skyrmions are a type of topological spin texture that great potential across a wide variety of technological applications. Here, Yu et al. study the thermally driven motion of Skyrmions and find a minimum temperature gradient for the motion of skyrmions two orders of magnitude smaller than for domain walls.
 Xiuzhen Yu
 , Fumitaka Kagawa
 & Yoshinori Tokura

Article
 Open AccessCompeting correlated states and abundant orbital magnetism in twisted monolayerbilayer graphene
Twisted monolayerbilayer graphene is an attractive platform to study the interplay between topology, magnetism and correlations in the flat bands. Here, using electrical transport measurements, the authors uncover a rich correlated phase diagram and identify a new insulating state that can be explained by intervalley coherence with broken time reversal symmetry.
 Minhao He
 , YaHui Zhang
 & Matthew Yankowitz

Article
 Open AccessOptical Ninvariant of graphene’s topological viscous Hall fluid
Graphene is the archetype for realizing twodimensional topological phases of matter. Here, the authors introduce a new topological classification connected to polarization transport, where the topological number is revealed in the spatiotemporal dispersion of the susceptibility tensor.
 Todd Van Mechelen
 , Wenbo Sun
 & Zubin Jacob

Article
 Open AccessGuided accumulation of active particles by topological design of a secondorder skin effect
Sustainable strategies for shepherding active particles are at the heart of many prospective applications. Here, Palacios et al. use the emerging topological properties of a microfluidic maze array to passively guide selfpropelled colloids from the interior to the edges of the device.
 Lucas S. Palacios
 , Serguei Tchoumakov
 & Adolfo G. Grushin

Article
 Open AccessMagneticfieldinduced robust zero Hall plateau state in MnBi_{2}Te_{4} Chern insulator
The antiferromagnetic topological insulator MnBi_{2}Te_{4} exhibits Chern and axion insulator phases at low magnetic field; however, its behaviour in high magnetic field has remained unexplored. Here, using transport measurements at high magnetic field, the authors report a zero Hall plateau composed of two counterpropagating edge channels.
 Chang Liu
 , Yongchao Wang
 & Yayu Wang

Article
 Open AccessLarge linear nonsaturating magnetoresistance and high mobility in ferromagnetic MnBi
Ferromagnetic systems rarely display a large or nonsaturating magnetoresistance, due to the low Fermi velocity of the predominant charge carrier. Here, the authors show that MnBi, a ferromagnet, bucks this trend, showing both large and nonsaturating magnetoresistance, and high charge carrier motilities.
 Yangkun He
 , Jacob Gayles
 & Claudia Felser

Article
 Open AccessEvidence for higher order topology in Bi and Bi_{0.92}Sb_{0.08}
The experimental realization of higher order topological insulator (HOTI) in solid state materials remains elusive. Here, Aggarwal et al. reveal hinge states on three edges of both Bi and Bi_{0.92}Sb_{0.08} (110) islands, supporting them as a class of HOTI.
 Leena Aggarwal
 , Penghao Zhu
 & Vidya Madhavan

Article
 Open AccessExperimental observation of topological Z_{2} excitonpolaritons in transition metal dichalcogenide monolayers
In this work light and matter have been coupled in a strong interaction between exciton resonances and topological photonic bands. The authors herein demonstrate a Z2 spinHall topological polaritonic phase enabling new coupling schemes in valleytronics and spintronics.
 Mengyao Li
 , Ivan Sinev
 & Alexander B. Khanikaev

Article
 Open AccessEvidence for onedimensional chiral edge states in a magnetic Weyl semimetal Co_{3}Sn_{2}S_{2}
Magnetic Weyl semimetals in the 2D limit may behave like 2D Chern insulators and host the quantum anomalous Hall effect at high temperatures. Here, the authors report the observation of linearly dispersing topological states confined to the edges of the kagome Co_{3}Sn terraces in the magnetic Weyl system Co_{3}Sn_{2}S_{2}.
 Sean Howard
 , Lin Jiao
 & Vidya Madhavan

Article
 Open AccessMajorana zero modes in impurityassisted vortex of LiFeAs superconductor
Despite the discovery of Majorana zero modes (MZM) in ironbased superconductors, sample inhomogeneity may destroy MZMs during braiding. Here, authors observe MZM in impurityassisted vortices due to tuning of the bulk Dirac fermions in a homogeneous superconductor LiFeAs.
 Lingyuan Kong
 , Lu Cao
 & Hong Ding

Article
 Open AccessSpinvalley locking and bulk quantum Hall effect in a noncentrosymmetric Dirac semimetal BaMnSb_{2}
Valley dependent spin polarization called spinvalley locking appears in absence of magnetism but it is limited to rare examples of transition metal dichalcogenides. Here, the authors report evidence of spinvalley locking and stacked quantum Hall effect in a bulk Dirac semimetal BaMnSb_{2}.
 J. Y. Liu
 , J. Yu
 & Z. Q. Mao

Article
 Open AccessControllable quantum point junction on the surface of an antiferromagnetic topological insulator
Recent advances in the identification and growth of antiferromagnetic topological insulators open the way to the manipulation of the chiral edge states that are topologically required at their step edges and domain walls. Here, the authors propose a quantum point junction formed by two types of edge states and discuss its applications in electron quantum optics.
 Nicodemos Varnava
 , Justin H. Wilson
 & David Vanderbilt

Article
 Open AccessObservation of a singular Weyl point surrounded by charged nodal walls in PtGa
In all experimentally observed Weyl semimetals so far, the Weyl points always appear in pairs in the momentum space. Here, the authors report one unpaired Weyl point without surface Fermi arc emerging at the center of the Brillouin zone, which is surrounded by charged Weyl nodal walls in PtGa.
 J.Z. Ma
 , Q.S. Wu
 & M. Shi

Article
 Open AccessVortex states in an acoustic Weyl crystal with a topological lattice defect
Here, the authors introduce a 3D Weyl metamaterial hosting modes bound to a 1D topological lattice defect. The modes carry nonzero orbital angular momentum locked to the direction of propagation, and they experimentally demonstrate the ability to emit acoustic vortices into free space.
 Qiang Wang
 , Yong Ge
 & Y. D. Chong

Article
 Open AccessMomentumspace signatures of Berry flux monopoles in the Weyl semimetal TaAs
Weyl semimetals exhibit Berry flux monopoles in momentumspace, but direct experimental evidence has remained elusive. Here, the authors reveal topologically nontrivial winding of the orbitalangularmomentum at the Weyl nodes and a chiralitydependent spinangularmomentum of the Weyl bands, as a direct signature of the Berry flux monopoles in TaAs.
 M. Ünzelmann
 , H. Bentmann
 & F. Reinert

Article
 Open AccessWavefront dislocations reveal the topology of quasi1D photonic insulators
Topological properties are defined from singularities of the wave functions delocalised in the bulk of the material, but most experimental manifestations remain indirect. Here, the authors observe a wavefront dislocation as a direct evidence of the phase singularity of the delocalised wave functions in 1D microwave photonic insulators.
 Clément Dutreix
 , Matthieu Bellec
 & Fabrice Mortessagne

Article
 Open AccessSpectral signatures of the surface anomalous Hall effect in magnetic axion insulators
Experimentally detectable signature of an axion insulator remains elusive. Here, the authors predict a topological phase diagram of MnBi_{2}Te_{4}/(Bi_{2}Te_{3})_{n} heterostructure, where the chiral hinge mode induced by the surface anomalous Hall conductivity is identified as a signature of an axion insulator state.
 Mingqiang Gu
 , Jiayu Li
 & Qihang Liu

Article
 Open AccessObservation of domain wall bimerons in chiral magnets
Domain wall skyrmions have been proposed but the experimental observation has been difficult. Here, the authors report experimental discovery of domain wall bimerons due to the interplay between magnetic anisotropy and DzyaloshinskiiMoriya interaction in chiral magnet CoZnMn(110) thin films.
 Tomoki Nagase
 , YeongGi So
 & Masahiro Nagao

Article
 Open AccessQuantized spin Hall conductance in a magnetically doped two dimensional topological insulator
The quantum spin Hall effect is expected not to survive the presence of magnetic impurities. Here, authors report full quantization at very low temperatures in HgTe quantum wells alloyed with a few percent of magnetic Mn atoms, due to Kondo screening.
 Saquib Shamim
 , Wouter Beugeling
 & Laurens W. Molenkamp

Article
 Open AccessOrigin of the quasiquantized Hall effect in ZrTe_{5}
A 3D quantum Hall effect has been reported in Dirac semimetal ZrTe_{5} due to a magneticfielddriven Fermi surface instability. Here, the authors show evidence of quasiquantized Hall response without Fermi surface instability, but they argue that it is due to the interplay of the intrinsic properties of ZrTe_{5} electronic structure and Dirac semimetallic character.
 S. Galeski
 , T. Ehmcke
 & J. Gooth

Article
 Open AccessNonAbelian threeloop braiding statistics for 3D fermionic topological phases
NonAbelian statistics plays a crucial role towards realizing topological quantum computation. Here, the authors discover new types of nonAbelian threeloop braiding statistics that can only be realized in 3D interacting fermionic systems.
 JingRen Zhou
 , QingRui Wang
 & ZhengCheng Gu

Article
 Open AccessKramers nodal line metals
Chiral crystals with spinorbit coupling (SOC) termed Kramers Weyl semimetals possess Weyl points at timereversal invariant momenta. Here, the authors propose a new class of topological materials with doubly degenerate lines connecting timereversal invariant momenta in achiral noncentrosymmetric materials with SOC.
 YingMing Xie
 , XueJian Gao
 & K. T. Law

Article
 Open AccessInteractioninduced topological phase transition and Majorana edge states in lowdimensional orbitalselective Mott insulators
Superconductivity induced on a topological insulator’s surface may realize Majorana modes. Here, Herbrych et al. predict that a large Coulomb interaction helps develop a spiral spin order, which is a topological state at the edge of a canonical superconductor with orbital degrees of freedom.
 J. Herbrych
 , M. Środa
 & E. Dagotto

Article
 Open AccessObservation of topological superconductivity in a stoichiometric transition metal dichalcogenide 2MWS_{2}
Topological superconductors are potentially important for future quantum computation, but they are very rare in nature. Here, the authors observe topological surface states acquiring a nodeless superconducting gap with similar magnitude as that of the bulk states in 2MWS_{2}, suggesting an intrinsic topological superconductor.
 Y. W. Li
 , H. J. Zheng
 & Y. L. Chen

Article
 Open AccessAndreev reflection of fractional quantum Hall quasiparticles
Andreev reflection is normally known to occur at a metalsuperconductor interface. Here, Hashisaka et al. observe an Andreevlike process in a narrow junction between fractional and integer quantum Hall states originating from a topological quantum manybody effect instead of superconductivity.
 M. Hashisaka
 , T. Jonckheere
 & K. Muraki

Article
 Open AccessEdge channels of brokensymmetry quantum Hall states in graphene visualized by atomic force microscopy
The brokensymmetry edge states that are the hallmark of the quantum Hall effect in graphene have eluded spatial measurements. Here, the authors spatially map the quantum Hall brokensymmetry edge states using atomic force microscopy and show a gapped ground state proceeding from the bulk through to the quantum Hall edge boundary.
 Sungmin Kim
 , Johannes Schwenk
 & Joseph A. Stroscio

Article
 Open AccessSpectroscopy of a tunable moiré system with a correlated and topological flat band
Twisted double bilayer graphene hosts flat bands that can be tuned with an electric field. Here, by using gatetuned scanning tunneling spectroscopy, the authors demonstrate the tunability of the flat band and reveal spectral signatures of correlated electron states and the topological nature of the flat band.
 Xiaomeng Liu
 , ChengLi Chiu
 & Ali Yazdani

Article
 Open AccessNanoscale realtime detection of quantum vortices at millikelvin temperatures
Previous work has shown the detection of quantum turbulence with mechanical resonators but with limited spatial and temporal resolution. Here, the authors demonstrate realtime detection of single quantum vortices in superfluid ^{4}He with millisecond and micron resolution at temperatures of 10 millikelvin.
 A. Guthrie
 , S. Kafanov
 & D. E. Presnov

Article
 Open AccessIntrinsic coupling between spatiallyseparated surface Fermiarcs in Weyl orbit quantum Hall states
The spatial distribution of the quantized transport due to the presence of Weyl orbits in topological semimetals remains elusive. Here, the authors report concomitant modulation of doublydegenerate quantum Hall states, evidencing intrinsic coupling between two spatially separated surface states in the Weyl orbits of a Dirac semimetal film.
 Shinichi Nishihaya
 , Masaki Uchida
 & Masashi Kawasaki

Article
 Open AccessIntercalated architecture of MA_{2}Z_{4} family layered van der Waals materials with emerging topological, magnetic and superconducting properties
The discovery of a new twodimensional van der Waals layered MoSi_{2}N_{4} material inspires many attentions. Here, the authors report intercalation strategies to explore a much wider range of MA_{2}Z_{4} family and predict amount of materials accessible to experimental verifications with emergent topological, magnetic or Ising superconductivity properties.
 Lei Wang
 , Yongpeng Shi
 & XingQiu Chen

Article
 Open AccessDiscovery of \({\hat{\boldsymbol{C}}}_2\) rotation anomaly in topological crystalline insulator SrPb
New class of topological crystalline insulators (TCI) have been proposed, but are yet to be experimentally evidenced. Here, the authors evidence two massless Dirac fermions protected by the combination of timereversal symmetry T and Ĉ_{2y} on the (010) surface of SrPb, confirming the Ĉ_{2} rotation anomaly in the new class of TCIs.
 Wenhui Fan
 , Simin Nie
 & Hong Ding

Article
 Open AccessGiant caxis nonlinear anomalous Hall effect in T_{d}MoTe_{2} and WTe_{2}
Certain materials without inversion symmetry may allow for a nonlinear anomalous Hall effect with conserved time reversal symmetry. Here, the authors report an extremely large caxis nonlinear anomalous Hall effect in the noncentrosymmetric T_{d} phase of MoTe_{2} and WTe_{2} without intrinsic magnetic order that is dominated by extrinsic scattering.
 Archana Tiwari
 , Fangchu Chen
 & Adam W. Tsen

Article
 Open AccessSpinorbit coupling induced splitting of YuShibaRusinov states in antiferromagnetic dimers
The influence of spinorbit coupling on the hybridization of Shiba states in dimers of magnetic atoms on superconducting surfaces remains unexplored. Here, the authors reveal a splitting of atomic Shiba orbitals due to spinorbit coupling and broken inversion symmetry in antiferromagnetically coupled Mn dimers placed on a Nb(110) surface.
 Philip Beck
 , Lucas Schneider
 & Roland Wiesendanger

Article
 Open AccessNonHermitian route to higherorder topology in an acoustic crystal
Losses, due to their nonHermitian nature, are generally disregarded or even considered harmful when looking for nontrivial topological phases. Here, the authors experimentally demonstrate that higherorder topology can emerge as a result of introducing losses in an acoustic crystal.
 He Gao
 , Haoran Xue
 & Baile Zhang

Article
 Open AccessManipulating Weyl quasiparticles by orbitalselective photoexcitation in WTe_{2}
Photoexcitation in Weyl semimetals is recently reported to induce topological phase transitions useful for ultrafast switching devices. Here, the authors predict that the symmetry of the atomic orbitals comprising the Weyl bands in response to linear light polarization allows for not only annihilation but also separation of Weyl quasiparticles.
 MengXue Guan
 , En Wang
 & Sheng Meng

Article
 Open AccessDiscovery of a weak topological insulating state and van Hove singularity in triclinic RhBi_{2}
Weak topological insulators (WTI) remain difficult to be observed in experiments. Here, the authors discover a WTI state in RhBi_{2}, where the topological surface states with saddle points result in a van Hove singularity along the (100) direction near Fermi energy.
 Kyungchan Lee
 , Gunnar F. Lange
 & Adam Kaminski

Article
 Open AccessHighfrequency rectifiers based on typeII Dirac fermions
Highfrequency rectifiers at terahertz regime are pivotal components in modern communication, whereas the drawbacks in semiconductor junctionsbased devices inhibit their usages. Here, the authors report electromagnetic rectification with high signaltonoise ratio driven by chiral Blochelectrons in typeII Dirac semimetal NiTe_{2}based device allowing for efficient THz detection.
 Libo Zhang
 , Zhiqingzi Chen
 & Wei Lu

Article
 Open AccessFragility of surface states in topological superfluid ^{3}He
Surface states in topological quantum matter are protected by their band structure. Here, on confined superfluid ^{3}He as a model for topological superconductors, the authors report experimental evidence on the fragility of surface Andreev bound states with respect to the details of surface scattering.
 P. J. Heikkinen
 , A. Casey
 & J. Saunders