News & Views |
Featured
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Comment |
Engineering quantum materials with chiral optical cavities
Strong light–matter coupling in quantum cavities provides a pathway to break fundamental materials symmetries, like time-reversal symmetry in chiral cavities. This Comment discusses the potential to realize non-equilibrium states of matter that have so far been only accessible in ultrafast and ultrastrong laser-driven materials.
- Hannes Hübener
- , Umberto De Giovannini
- & Angel Rubio
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Article |
Observation of fluctuation-mediated picosecond nucleation of a topological phase
Time-resolved X-ray scattering is utilized to demonstrate an ultrafast 300 ps topological phase transition to a skyrmionic phase. This transition is enabled by the formation of a transient topological fluctuation state.
- Felix Büttner
- , Bastian Pfau
- & Stefan Eisebitt
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Review Article |
Emergent phenomena and proximity effects in two-dimensional magnets and heterostructures
This Review summarizes recent progress in exploring the intrinsic magnetism of atomically thin van der Waals materials, manipulation of their magnetism by tuning the interlayer coupling, and device structures for spin- and valleytronic applications.
- Bevin Huang
- , Michael A. McGuire
- & Xiaodong Xu
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Article |
Polar meron lattice in strained oxide ferroelectrics
Merons are topological structures, but these have yet to be directly observed in ferroelectrics. Here, by epitaxially straining PbTiO3 on a SmScO3 substrate, electron microscopy and phase-field modelling allow the morphology and distribution of merons to be observed.
- Y. J. Wang
- , Y. P. Feng
- & X. L. Ma
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Article |
Visualizing coexisting surface states in the weak and crystalline topological insulator Bi2TeI
Bi2TeI is identified as a dual topological insulator. It is a weak topological insulator with metallic states at the (010) surfaces and a topological crystalline insulator at the (001) surfaces.
- Nurit Avraham
- , Abhay Kumar Nayak
- & Haim Beidenkopf
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News & Views |
Marriage of topology and magnetism
A monolayer topological insulator is magnetized by proximity to a layered antiferromagnetic insulator.
- Cui-Zu Chang
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Letter |
Magnetic proximity and nonreciprocal current switching in a monolayer WTe2 helical edge
The coupling between magnetism and topology is studied in a van der Waals heterostructure.
- Wenjin Zhao
- , Zaiyao Fei
- & David H. Cobden
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News & Views |
One compound with two distinct topological states
Two distinct topological states that are closely tied to the spin configurations of a layered compound, here MnBi2Te4, have been demonstrated. Such control of the topological state should enable new opportunities to realize quantum and spintronic devices.
- Peng Wei
- & Jagadeesh S. Moodera
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Article |
Concurrence of quantum anomalous Hall and topological Hall effects in magnetic topological insulator sandwich heterostructures
The coexistence of chiral edge states and chiral spin textures in magnetic topological insulator sandwiches provides a platform for proof-of-concept dissipationless spin-textured spintronic applications.
- Jue Jiang
- , Di Xiao
- & Cui-Zu Chang
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Letter |
Black phosphorus as a bipolar pseudospin semiconductor
Anisotropic honeycomb crystal of black phosphorous is found to have pseudospin polarization greater than 95% at room temperature, attributed to the merging of Dirac cones. This bipolar pseudospin semiconductor may be useful for pseudospintronics.
- Sung Won Jung
- , Sae Hee Ryu
- & Keun Su Kim
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News & Views |
Topology and correlations on the kagome lattice
Both a Dirac band and a flat band — signatures of topology and correlation — are found in a prototypical antiferromagnetic kagome lattice compound FeSn.
- Nirmal J. Ghimire
- & Igor I. Mazin
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Letter |
Robust axion insulator and Chern insulator phases in a two-dimensional antiferromagnetic topological insulator
A large longitudinal resistance and zero Hall plateau—hallmarks of an axion insulator—are found in MnBi2Te4. Moreover, a moderate magnetic field drives a quantum phase transition to a Chern insulator phase with zero longitudinal resistance and quantized Hall resistance h/e2.
- Chang Liu
- , Yongchao Wang
- & Yayu Wang
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Article |
Dirac fermions and flat bands in the ideal kagome metal FeSn
A prototypical kagome metal with magnetic and topological properties is identified.
- Mingu Kang
- , Linda Ye
- & Riccardo Comin
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News & Views |
Thermoelectrics with a twist
Inducing a topological phase transition by applying pressure is shown to be a successful strategy for improving the performance of thermoelectric materials.
- Qiang Li
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News & Views |
Shrewd detectives find a dissipation channel
The non-contact friction between a metal tip and a Bi2Te3 surface is controlled by a single charge in an image potential state.
- Bernd Gotsmann
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Article |
Mechanical dissipation via image potential states on a topological insulator surface
Non-contact dissipation measurements reveal an interplay between electronic states and nanomechanics in Bi2Te3, a canonical topological insulator with protected metallic surface states.
- D. Yildiz
- , M. Kisiel
- & E. Meyer
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Article |
Enhancement of thermoelectric performance across the topological phase transition in dense lead selenide
By applying a pressure of 2.8 GPa using a diamond anvil cell, a topological phase transition is found to occur in Cr-doped PbSe. This enables a thermoelectric figure of merit ZT of 1.7 at room temperature.
- Liu-Cheng Chen
- , Pei-Qi Chen
- & Xiao-Jia Chen
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Article |
Directional massless Dirac fermions in a layered van der Waals material with one-dimensional long-range order
A one-dimensional Dirac-like band is observed in a layer van der Waals material, expanding the arsenal of 2D systems.
- T. Y. Yang
- , Q. Wan
- & N. Xu
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Letter |
Robust zero-energy modes in an electronic higher-order topological insulator
A higher-order topological insulator is realized in a breathing kagome lattice built by patterning CO molecules on a Cu(111) surface.
- S. N. Kempkes
- , M. R. Slot
- & C. Morais Smith
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Article |
Mapping spin–charge conversion to the band structure in a topological oxide two-dimensional electron gas
A very large spin-to-charge conversion arising from a combination of the Rashba effect and topologically non-trivial states is realized at the interface of strontium titanate and aluminium, with implications for the role of topology in memory and transistor designs.
- Diogo C. Vaz
- , Paul Noël
- & Manuel Bibes
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News & Views |
Conjuring Majorana with synthetic magnetism
Majorana zero modes — useful for quantum computing — are revealed in carbon nanotubes by utilizing a synthetic spin–orbit interaction.
- Ali Yazdani
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Letter |
Synthetic spin–orbit interaction for Majorana devices
A magnetic texture is used to synthetically induce a large spin–orbit interaction in a carbon nanotube, and signatures of Majorana zero modes—promising for quantum computing applications—are observed.
- M. M. Desjardins
- , L. C. Contamin
- & T. Kontos
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Letter |
Spin chirality fluctuation in two-dimensional ferromagnets with perpendicular magnetic anisotropy
Evidence for spin chirality fluctuations in two-dimensional ferromagnets is provided by magnetotransport measurements.
- Wenbo Wang
- , Matthew W. Daniels
- & Weida Wu
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Article |
Spatially dispersive circular photogalvanic effect in a Weyl semimetal
A spatially dispersive photoresponse is found in a topological semimetal.
- Zhurun Ji
- , Gerui Liu
- & Ritesh Agarwal
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Letter |
Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te)
High-resolution spectroscopy supports the presence of Majorana bound states in an iron-based topological superconductor.
- T. Machida
- , Y. Sun
- & T. Tamegai
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News & Views |
Lighting up Weyl semimetals
By measuring the photocurrent from illuminated Weyl semimetals, an optical signature of topological properties arising from Weyl fermions has been revealed, highlighting nonlinear optical effects and applications of Weyl semimetals.
- Hongming Weng
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Article |
Ultrahigh conductivity in Weyl semimetal NbAs nanobelts
High mobility and high carrier density are found in the Weyl semimetal NbAs. This is attributed to the low dissipation of disorder-tolerant Fermi arcs.
- Cheng Zhang
- , Zhuoliang Ni
- & Faxian Xiu
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Letter |
A gap-protected zero-Hall effect state in the quantum limit of the non-symmorphic metal KHgSb
Zero Hall effect is found in the quantum limit of KHgSb. This observation is attributed to counter-propagating double quantum spin Hall states.
- Sihang Liang
- , Satya Kushwaha
- & N. P. Ong
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Article |
Colossal mid-infrared bulk photovoltaic effect in a type-I Weyl semimetal
A large bulk photovoltaic effect is observed in the type-I Weyl semimetal TaAs, and attributed to the diverging Berry curvature of the Weyl nodes.
- Gavin B. Osterhoudt
- , Laura K. Diebel
- & Kenneth S. Burch
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Article |
Nonlinear photoresponse of type-II Weyl semimetals
A large photoresponse is observed in the type-II Weyl semimetal TaIrTe4, and attributed to the diverging Berry curvature of the Weyl nodes.
- Junchao Ma
- , Qiangqiang Gu
- & Dong Sun
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Letter |
Nonlinear anomalous Hall effect in few-layer WTe2
A nonlinear anomalous Hall effect, allowed for certain point group symmetries, is observed in metallic WTe2.
- Kaifei Kang
- , Tingxin Li
- & Kin Fai Mak
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Comment |
Nanoelectronics based on topological structures
Topological structures have considerable potential in nanoelectronics and new device concepts. They are key to the design and understanding of novel functionalities in ferroic materials — that is, materials that have one or more types of built-in order such as magnetic, ferroelectric, ferroelastic and multiferroic materials.
- Jan Seidel
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News & Views |
Trapping sound at corners
Higher-order topological acoustic metamaterials on kagome lattices, which host topologically protected corner states, can confine sound at corners. This may lead to applications of acoustic metamaterials in local acoustic field enhancement, trapping and manipulating of particles, and acoustic sensing and probing.
- Zhengyou Liu
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Letter |
Acoustic higher-order topological insulator on a kagome lattice
A second-order topological insulator in an acoustical metamaterial with a breathing kagome lattice, supporting one-dimensional edge states and zero-dimensional corner states is demonstrated.
- Haoran Xue
- , Yahui Yang
- & Baile Zhang
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Article |
Observation of higher-order topological acoustic states protected by generalized chiral symmetry
The physics of a second-order topological insulator, such as two-dimensional polarization, one-dimensional edge states and zero-dimensional corner states, are demonstrated experimentally in an acoustic breathing kagome lattice.
- Xiang Ni
- , Matthew Weiner
- & Alexander B. Khanikaev
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Article |
Epitaxial growth of ultraflat stanene with topological band inversion
A flat stanene layer can be grown on Cu (111) by MBE growth, exhibiting topological properties as revealed by a combination of ARPES, STM and DFT calculations.
- Jialiang Deng
- , Bingyu Xia
- & J. G. Hou
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Article |
Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures
Ferroelectric control of skyrmion density and stability is realized in a perovskite heterostructure.
- Lingfei Wang
- , Qiyuan Feng
- & Tae Won Noh
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News & Views |
Chirality meets topology
By considering the topology of chiral crystals, a new type of massless fermion, connected with giant arc-like surface states, are predicted. Such Kramers–Weyl fermions should manifest themselves in a wide variety of chiral materials.
- Chandra Shekhar
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Article |
On-chip valley topological materials for elastic wave manipulation
Topologically protected edge states can be observed when combining two Si-based phononic crystals of opposite phases, as well as on-chip elastic wave splitting via partition of edges states at the intersection of topological channels.
- Mou Yan
- , Jiuyang Lu
- & Zhengyou Liu
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News & Views |
A missing step is a key step
Physicists are searching for superconducting materials that can host Majoranas. New evidence for these elusive particles is provided by missing Shapiro steps in a Josephson effect mediated by an accidental Dirac semimetal.
- Fan Zhang
- & Wei Pan
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News & Views |
Ferromagnetism in a topological semimetal
The van der Waals material Fe3–xGeTe2 is shown to be a strong candidate for a ferromagnetic nodal-line semimetal with a very large anomalous Hall effect.
- D. A. Pesin
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News & Views |
Switching by topological insulators
Magnetization in magnetoresistive memory devices can be controlled at room temperature by spin–orbit torques originating from the surface states of topological insulators.
- Chi-Feng Pai
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Article |
Room-temperature high spin–orbit torque due to quantum confinement in sputtered BixSe(1–x) films
Sputtered BixSe(1–x) thin films can generate very large current-induced spin–orbit torque, capable to switch both in-plane and out-of-plane magnetized CoFeB-based structures deposited on top, at room temperature.
- Mahendra DC
- , Roberto Grassi
- & Jian-Ping Wang
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Letter |
Observation of magnetic vortex pairs at room temperature in a planar α-Fe2O3/Co heterostructure
Magnetic vortices formed in antiferromagnetic haematite and imprinted on a Co ferromagnetic over-layer have been observed using X-ray magnetic linear and circular dichroism photoemission electron microscopy. These vortex pairs can be manipulated by the application of magnetic fields.
- F. P. Chmiel
- , N. Waterfield Price
- & P. G. Radaelli
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News & Views |
The effective way
A theoretical framework for the design of so-called perturbative metamaterials, based on weakly interacting unit cells, has led to the experimental demonstration of a quadrupole topological insulator.
- Michel Fruchart
- & Vincenzo Vitelli
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Article |
Designing perturbative metamaterials from discrete models
A perturbative method is proposed for the systematic design of mechanical metamaterials, where each element of the discrete model is associated with individual geometric features of the metamaterial, through the weak interaction between the unit cells.
- Kathryn H. Matlack
- , Marc Serra-Garcia
- & Chiara Daraio
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Article |
Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides
Type-I and type-II bulk Dirac cones and ladders of topological surface states are shown to form in six different transition-metal dichalcogenides.
- M. S. Bahramy
- , O. J. Clark
- & P. D. C. King
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Editorial |
Stranger things
From a combined effort by theorists, materials scientists and spectroscopists, topology has moved from a purely mathematical idea to the realization of unique properties in several condensed matter systems.
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Review Article |
Quantum materials discovery from a synthesis perspective
The exploration of the properties and applications of quantum materials relies on advances in synthesis techniques. The approaches pursued to realize thin films and other materials revealing emergent quantum behaviour are reviewed here.
- Nitin Samarth