DOCSLIB.ORG

Crystal Shape Engineering of Topological Crystalline Insulator Snte Microcrystals and Nanowires with Huge Thermal Activation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Crystal Shape Engineering of Topological Crystalline Insulator Snte Microcrystals and Nanowires with Huge Thermal Activation Article pubs.acs.org/crystal Crystal Shape Engineering of Topological Crystalline Insulator SnTe Microcrystals and Nanowires with Huge Thermal Activation Energy Gap † † Muhammad Safdar, Qisheng Wang, Misbah Mirza, Zhenxing Wang, and Jun He* National Center for Nanoscience and Technology, Beijing 100190, P.R. China *S Supporting Information ABSTRACT: Since different high-symmetrical crystal planes of topological crystalline insulator possess their own topological electronic structure, manipulating crystal shapes with distinct facets of SnTe nanostructures is crucial for the realization of desired topological surface properties. Here, we developed crystal shapes engineering for the controllable synthesis of SnTe microcrystals and nanowires with specific exposed surfaces by optimizing experimental parameters in the chemical vapor deposition process. Crystal shapes of SnTe microcrystals are tailored from {100} surface-covered cubes, {100} and {111} surface-coated truncated octahedron, to a {111} surface-terminated octahedron. Significantly, with gold nanoparticles as the catalyst, two novel SnTe nanowires, octahedron-attached SnTe nanowires, and truncated octahedron-assisted SnTe nanowires, are achieved. The requirement of minimizing the overall surface energy drives the formation of various crystal shapes of SnTe microcrystals and nanowires. In addition, SnTe nanowires possess a huge thermal activation energy gap (350 ± 17 meV), 14 times larger than the energy scale of room temperature. This huge thermal activation energy gap can protect topological surface states of SnTe nanowires against the disturbance of thermal excitation. Our work provides the building block for the realization of unique topological surface effects on specific facets and novel spintronic devices. 1. INTRODUCTION Low-dimensional TI nanostructures holds superior merits in The discovery of topological crystalline insulators (TCIs) the investigations of the surface topological nature due to their 1−4 large surface-to-volume ratio, which tremendously enhances the greatly extends the family of topological insulators (TIs). 10−12 TCIs are different from conventional TIs in that the crystalline contribution of topological surface carriers. In addition, symmetry takes the place of the role of time-reversal symmetry low-dimensional TI nanostructures are the key for the in guaranteeing the topological protection.1,3,5 In the fundamental investigation of materials such as unique quantum mechanics phenomena and applications such as the nanoscale topological crystalline insulator, highly symmetric crystal 10,11,13 surfaces such as {001}, {110}, and {111} possess gapless electronic and spintronic devices. As a result, it is metallic surface states. Since the theoretical predication of tin extremely important to develop the synthesis strategy for high- 2 6,7 quality single crystalline SnTe nanostructures. telluride (SnTe) and its related alloys PbxSn1−x(Te, Se) as TCIs, they have quickly sparked the immense research interest SnTe has a rocksalt structure with space group Fm3m̅.It of theorists and experimentalists from all over the world. Soon holds a special mirror symmetry in the face-centered-cubic after theoretical predication, the Dirac cones of SnTe and its Brillouin zone. Importantly, the stoichiometric ratio of SnTe is related alloys Pb Sn − (Te, Se) on surface (001) are confirmed much simpler compared with other TCIs, such as Pb1−xSnx(Te, x 1 x 6,7 by angle-resolved photoemission spectra.4,8 Significantly, the Se), which makes it easier to be synthesized. In the past few ff electronic structure of SnTe or PbxSn1−x(Te, Se) is proved to years, considerable e ort has been devoted to the fabrication of be continuously tunable by applying external perturbation, such 2,9 as elastic strain and magnetic field. This novel property Received: February 12, 2014 makes TCIs a promising materials system in the applications of Revised: March 16, 2014 tunable electronic and spintronic devices. Published: March 21, 2014 © 2014 American Chemical Society 2502 dx.doi.org/10.1021/cg5002122 | Cryst. Growth Des. 2014, 14, 2502−2509 Crystal Growth & Design Article Figure 1. (a) SEM image and (b) magnified SEM image of smooth nanowires deposited at 550 °C. (c) SEM image of beaded nanowires and smooth nanowire mixture deposited at 500 °C. (d) Magnified SEM image of single-beaded nanowire. (e) SEM image of microcrystal-assisted nanowires deposited at 450 °C. (f) Magnified SEM image of microcrystal-assisted nanowires. one-dimensional SnTe nanostructures by solution-based temperature (25 meV).24 Inspired by our previous work where methods.14,15 However, the synthesized SnTe nanorods or we found the Aharonov−Bohm (AB) interference of SnTe nanowires are short and polycrystalline, which cannot meet the nanowire remains robust at near liquid-nitrogen temperature requirements of materials for the observation of topological (40 K), we believe SnTe nanowires have a great thermal surface nature and the utilization of surface states in activation thermal energy gap, which protects topological microelectronics and spintronics. Recently, our group, for the surface states against the disturbance of thermal excitations. first time, successfully synthesized the highly single crystalline Here, the growth of perfect cubic and octahedral SnTe SnTe nanowire via gold (Au)-catalyst chemical vapor micorcrystals and truncated octahedral SnTe micorcrystals with deposition (CVD) and realized the observation of topological special facets are demonstrated via the chemical vapor surface states in SnTe nanowire by magnet-transport measure- deposition (CVD) process. It is worth noting that the crystal ments.16 This work supplies the basis of materials for the shapes can be precisely manipulated by tailoring the deposition experimental research in low-dimensional TCIs and opens the temperature due to the fact that the dominated facets with the door for the applications of SnTe nanowire as nanoelectronics lowest surface energy are different at the distinguishing and spintronics devices. Subsequently, Z. Li et al. applied the temperature region. Significantly, the competing relations of CVD method to realize the growth of smooth SnTe nanowires surface energy between the {111} and {100} surfaces leads to dominated by the {100} crystal plane and zigzag SnTe unique octahedral microcrystal-attached SnTe nanowires and nanowires with both {100} and {111} facets, combining truncated octahedral microcrystal-assisted SnTe nanowires at density functional theory (DFT) calculations.17 However, the the intermediate temperature range. Specific crystal shapes with morphologies of SnTe nanowires with distinct highly distinct facets obtained in our work provides building blocks for symmetric crystal surfaces are far more than smooth and the realization of novel topological surface effect and spintronic zigzag nanowires, as demonstrated in this work. And the devices. Moreover, by investigating temperature-dependent structural evolution processes of different morphology are very conductive behavior, we found thermal activation energy gap of complicated due to the competing growth of different facets at the synthesized single crystalline SnTe nanowire reaches up to ± different temperatures, since different highly symmetry crystal 350 17 meV, which is 14 times larger than the energy scale of ∼ 21 surfaces hold their own special topological surface states.7,18 room temperature ( 25 meV). We believe the huge thermal Controllable synthesis and clear understanding of the growth activation energy gap is crucial for the observation of apparent Aharonov−Bohm (AB) interference of the SnTe nanowire at a mechanism of various low-dimensional SnTe nanostructures 16 with distinct highly symmetric crystal surfaces is essential for relatively high temperature (40 K) in our previous work. the realization of strongly expected quantum mechanics Thus SnTe nanowires are the promising materials to achieve phenomena and device applications. room-temperature observation of unique quantum mechanics Furthermore, in order to realize the practical applications of behavior and applications of low-dissipation nanoscale dissipationless electronic devices, the quantum mechanics electronic and spintronic devices. behaviors are intensely expected to be obtained at ambient, or at least liquid-nitrogen, temperatures.19 However, current 2. EXPERIMENTAL SECTION observation of the topological surface states is all at low 2.1. Synthesis of SnTe Nanowires and Microcrystals. SnTe 10,11,13,20,21 temperature, typically at liquid-helium temperature. nanowires and microcrystals were synthesized using a horizontal This is because low temperature can prevent the fragile vacuum tube furnace with single temperature zone. Si substrates topological surface states from the disturbance of bulk carriers covered with an 8 nm gold (Au) layer were used as the growth induced by thermal excitations.10,22,23 As a result, for the substrates. SnTe powder was loaded (99.99%, alfa aesar) in the center of quartz tube. Si substrates covered by Au thin film were placed in the purpose of pragmatic needs, TIs must have the large thermal fi activation energy gap, which makes TIs more immune from downstream area. The quartz tube was rst sealed and then it was evacuated and flushed a few times with high purity Ar gas in order to bulk carriers at relative high temperature. However, thermal 24−27 provide an oxygen-free environment. During the experiment, Ar gas activation energy gap of most reported TIs is very low. For was fed with
Load more

Recommended publications
  • Edge States in Topological Magnon Insulators
    PHYSICAL REVIEW B 90, 024412 (2014) Edge states in topological magnon insulators Alexander Mook,1 Jurgen¨ Henk,2 and Ingrid Mertig1,2 1Max-Planck-Institut fur¨ Mikrostrukturphysik, D-06120 Halle (Saale), Germany 2Institut fur¨ Physik, Martin-Luther-Universitat¨ Halle-Wittenberg, D-06099 Halle (Saale), Germany (Received 15 May 2014; revised manuscript received 27 June 2014; published 18 July 2014) For magnons, the Dzyaloshinskii-Moriya interaction accounts for spin-orbit interaction and causes a nontrivial topology that allows for topological magnon insulators. In this theoretical investigation we present the bulk- boundary correspondence for magnonic kagome lattices by studying the edge magnons calculated by a Green function renormalization technique. Our analysis explains the sign of the transverse thermal conductivity of the magnon Hall effect in terms of topological edge modes and their propagation direction. The hybridization of topologically trivial with nontrivial edge modes enlarges the period in reciprocal space of the latter, which is explained by the topology of the involved modes. DOI: 10.1103/PhysRevB.90.024412 PACS number(s): 66.70.−f, 75.30.−m, 75.47.−m, 85.75.−d I. INTRODUCTION modes causes a doubling of the period of the latter in reciprocal space. Understanding the physics of electronic topological in- The paper is organized as follows. In Sec. II we sketch the sulators has developed enormously over the past 30 years: quantum-mechanical description of magnons in kagome lat- spin-orbit interaction induces band inversions and, thus, yields tices (Sec. II A), Berry curvature and Chern number (Sec. II B), nonzero topological invariants as well as edge states that are and the Green function renormalization method for calculating protected by symmetry [1–3].
    [Show full text]
  • Topological Insulators Physicsworld.Com Topological Insulators This Newly Discovered Phase of Matter Has Become One of the Hottest Topics in Condensed-Matter Physics
    Feature: Topological insulators physicsworld.com Topological insulators This newly discovered phase of matter has become one of the hottest topics in condensed-matter physics. It is hard to understand – there is no denying it – but take a deep breath, as Charles Kane and Joel Moore are here to explain what all the fuss is about Charles Kane is a As anyone with a healthy fear of sticking their fingers celebrated by the 2010 Nobel prize – that inspired these professor of physics into a plug socket will know, the behaviour of electrons new ideas about topology. at the University of in different materials varies dramatically. The first But only when topological insulators were discov- Pennsylvania. “electronic phases” of matter to be defined were the ered experimentally in 2007 did the attention of the Joel Moore is an electrical conductor and insulator, and then came the condensed-matter-physics community become firmly associate professor semiconductor, the magnet and more exotic phases focused on this new class of materials. A related topo- of physics at University of such as the superconductor. Recent work has, how- logical property known as the quantum Hall effect had California, Berkeley ever, now uncovered a new electronic phase called a already been found in 2D ribbons in the early 1980s, and a faculty scientist topological insulator. Putting the name to one side for but the discovery of the first example of a 3D topologi- at the Lawrence now, the meaning of which will become clear later, cal phase reignited that earlier interest. Given that the Berkeley National what is really getting everyone excited is the behaviour 3D topological insulators are fairly standard bulk semi- Laboratory, of materials in this phase.
    [Show full text]
  • On the Topological Immunity of Corner States in Two-Dimensional Crystalline Insulators ✉ Guido Van Miert1 and Carmine Ortix 1,2
    www.nature.com/npjquantmats ARTICLE OPEN On the topological immunity of corner states in two-dimensional crystalline insulators ✉ Guido van Miert1 and Carmine Ortix 1,2 A higher-order topological insulator (HOTI) in two dimensions is an insulator without metallic edge states but with robust zero- dimensional topological boundary modes localized at its corners. Yet, these corner modes do not carry a clear signature of their topology as they lack the anomalous nature of helical or chiral boundary states. Here, we demonstrate using immunity tests that the corner modes found in the breathing kagome lattice represent a prime example of a mistaken identity. Contrary to previous theoretical and experimental claims, we show that these corner modes are inherently fragile: the kagome lattice does not realize a higher-order topological insulator. We support this finding by introducing a criterion based on a corner charge-mode correspondence for the presence of topological midgap corner modes in n-fold rotational symmetric chiral insulators that explicitly precludes the existence of a HOTI protected by a threefold rotational symmetry. npj Quantum Materials (2020) 5:63 ; https://doi.org/10.1038/s41535-020-00265-7 INTRODUCTION a manifestation of the crystalline topology of the D − 1 edge 1234567890():,; Topology and geometry find many applications in contemporary rather than of the bulk: the corresponding insulating phases have physics, ranging from anomalies in gauge theories to string been recently dubbed as boundary-obstructed topological 38 theory. In condensed matter physics, topology is used to classify phases and do not represent genuine (higher-order) topological defects in nematic crystals, characterize magnetic skyrmions, and phases.
    [Show full text]
  • Topological Insulators: Electronic Structure, Material Systems and Its Applications
    Network for Computational Nanotechnology UC Berkeley, Univ. of Illinois, Norfolk(NCN) State, Northwestern, Purdue, UTEP Topological Insulators: Electronic structure, material systems and its applications Parijat Sengupta Network for Computational Nanotechnology Electrical and Computer Engineering Purdue University Complete set of slides from my final PhD defense Advisor : Prof. Gerhard Klimeck A new addition to the metal-insulator classification Nature, Vol. 464, 11 March, 2010 Surface states Metal Trivial Insulator Topological Insulator 2 2 Tracing the roots of topological insulator The Hall effect of 1869 is a start point How does the Hall resistance behave for a 2D set-up under low temperature and high magnetic field (The Quantum Hall Effect) ? 3 The Quantum Hall Plateau ne2 = σ xy h h = 26kΩ e2 Hall Conductance is quantized B Cyclotron motion Landau Levels eB E = ω (n + 1 ), ω = , n = 0,1,2,... n c 2 c mc 4 Plateau and the edge states Ext. B field Landau Levels Skipping orbits along the edge Skipping orbits induce a gapless edge mode along the sample boundary Question: Are edge states possible without external B field ? 5 Is there a crystal attribute that can substitute an external B field Spin orbit Interaction : Internal B field 1. Momentum dependent force, analogous to B field 2. Opposite force for opposite spins 3. Energy ± µ B depends on electronic spin 4. Spin-orbit strongly enhanced for atoms of large atomic number Fundamental difference lies under a Time Reversal Symmetric Operation Time Reversal Symmetry Violation 1. Quantum
    [Show full text]
  • A Topological Insulator Surface Under Strong Coulomb, Magnetic and Disorder Perturbations
    LETTERS PUBLISHED ONLINE: 12 DECEMBER 2010 | DOI: 10.1038/NPHYS1838 A topological insulator surface under strong Coulomb, magnetic and disorder perturbations L. Andrew Wray1,2,3, Su-Yang Xu1, Yuqi Xia1, David Hsieh1, Alexei V. Fedorov3, Yew San Hor4, Robert J. Cava4, Arun Bansil5, Hsin Lin5 and M. Zahid Hasan1,2,6* Topological insulators embody a state of bulk matter contact with large-moment ferromagnets and superconductors for characterized by spin-momentum-locked surface states that device applications11–17. The focus of this letter is the exploration span the bulk bandgap1–7. This highly unusual surface spin of topological insulator surface electron dynamics in the presence environment provides a rich ground for uncovering new of magnetic, charge and disorder perturbations from deposited phenomena4–24. Understanding the response of a topological iron on the surface. surface to strong Coulomb perturbations represents a frontier Bismuth selenide cleaves on the (111) selenium surface plane, in discovering the interacting and emergent many-body physics providing a homogeneous environment for deposited atoms. Iron of topological surfaces. Here we present the first controlled deposited on a Se2− surface is expected to form a mild chemical study of topological insulator surfaces under Coulomb and bond, occupying a large ionization state between 2C and 3C 25 magnetic perturbations. We have used time-resolved depo- with roughly 4 µB magnetic moment . As seen in Fig. 1d the sition of iron, with a large Coulomb charge and significant surface electronic structure after heavy iron deposition is greatly magnetic moment, to systematically modify the topological altered, showing that a significant change in the surface electronic spin structure of the Bi2Se3 surface.
    [Show full text]
  • Topological Insulator Interfaced with Ferromagnetic Insulators: ${\Rm{B}}
    PHYSICAL REVIEW MATERIALS 4, 064202 (2020) Topological insulator interfaced with ferromagnetic insulators: Bi2Te3 thin films on magnetite and iron garnets V. M. Pereira ,1 S. G. Altendorf,1 C. E. Liu,1 S. C. Liao,1 A. C. Komarek,1 M. Guo,2 H.-J. Lin,3 C. T. Chen,3 M. Hong,4 J. Kwo ,2 L. H. Tjeng ,1 and C. N. Wu 1,2,* 1Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany 2Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan 3National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan 4Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (Received 28 November 2019; revised manuscript received 17 March 2020; accepted 22 April 2020; published 3 June 2020) We report our study about the growth and characterization of Bi2Te3 thin films on top of Y3Fe5O12(111), Tm3Fe5O12(111), Fe3O4(111), and Fe3O4(100) single-crystal substrates. Using molecular-beam epitaxy, we were able to prepare the topological insulator/ferromagnetic insulator heterostructures with no or minimal chemical reaction at the interface. We observed the anomalous Hall effect on these heterostructures and also a suppression of the weak antilocalization in the magnetoresistance, indicating a topological surface-state gap opening induced by the magnetic proximity effect. However, we did not observe any obvious x-ray magnetic circular dichroism (XMCD) on the Te M45 edges. The results suggest that the ferromagnetism induced by the magnetic proximity effect via van der Waals bonding in Bi2Te3 is too weak to be detected by XMCD, but still can be observed by electrical transport measurements.
    [Show full text]
  • Topological Insulator Materials for Advanced Optoelectronic Devices
    Book Chapter for <<Advanced Topological Insulators>> Topological insulator materials for advanced optoelectronic devices Zengji Yue1,2*, Xiaolin Wang1,2 and Min Gu3 1Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500, Australia 2ARC Centre for Future Low-Energy Electronics Technologies, Australia 3Laboratory of Artificial-Intelligence Nanophotonics, School of Science, RMIT University, Melbourne, Victoria 3001, Australia *Corresponding email: [email protected] Abstract Topological insulators are quantum materials that have an insulating bulk state and a topologically protected metallic surface state with spin and momentum helical locking and a Dirac-like band structure.(1-3) Unique and fascinating electronic properties, such as the quantum spin Hall effect, topological magnetoelectric effects, magnetic monopole image, and Majorana fermions, are expected from topological insulator materials.(4, 5) Thus topological insulator materials have great potential applications in spintronics and quantum information processing, as well as magnetoelectric devices with higher efficiency.(6, 7) Three-dimensional (3D) topological insulators are associated with gapless surface states, and two-dimensional (2D) topological insulators with gapless edge states.(8) The topological surface (edge) states have been mainly investigated by first-principle theoretical calculation, electronic transport, angle- resolved photoemission spectroscopy (ARPES), and scanning tunneling microscopy (STM).(9) A variety of compounds have been identified as 2D or 3D topological insulators, including HgTe/CdTe, Bi2Se3, Bi2Te3, Sb2Te3, SmB6, BiTeCl, Bi1.5Sb0.5Te1.8Se1.2, and so on.(9-12) On the other hand, topological insulator materials also exhibit a number of excellent optical properties, including Kerr and Faraday rotation, ultrahigh bulk refractive index, near-infrared frequency transparency, unusual electromagnetic scattering and ultra-broadband surface plasmon resonances.
    [Show full text]
  • Room Temperature Magnetization Switching in Topological Insulator
    Room temperature magnetization switching in topological insulator-ferromagnet heterostructures by spin-orbit torques Yi Wang1*, Dapeng Zhu1*, Yang Wu1, Yumeng Yang1, Jiawei Yu1, Rajagopalan Ramaswamy1, Rahul Mishra1, Shuyuan Shi1,2, Mehrdad Elyasi1, Kie-Leong Teo1, Yihong Wu1, and Hyunsoo Yang1,2 1Department of Electrical and Computer Engineering, National University of Singapore, 117576, Singapore 2Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546 Singapore *These authors contributed equally to this work. Correspondence and requests for materials should be addressed to H.Y. (email: [email protected]). Topological insulators (TIs) with spin momentum locked topological surface states (TSS) are expected to exhibit a giant spin-orbit torque (SOT) in the TI/ferromagnet systems. To date, the TI SOT driven magnetization switching is solely reported in a Cr doped TI at 1.9 K. Here, we directly show giant SOT driven magnetization switching in a Bi2Se3/NiFe heterostructure at room temperature captured using a magneto-optic Kerr effect microscope. We identify a large charge-to-spin conversion efficiency of ~1–1.75 in the thin TI films, where the TSS is dominant. In addition, we find the current density required for the magnetization switching is extremely low, ~6×105 A cm–2, which is one to two orders of magnitude smaller than that with heavy metals. Our demonstration of room temperature magnetization switching of a conventional 3d ferromagnet using Bi2Se3 may lead to potential innovations in TI based spintronic applications. 1 The spin currents generated by charge currents via the spin Hall effect1-4 and/or Rashba-Edelstein effect5,6 can exert spin-orbit torques (SOTs) on the adjacent FM layer and result in the current induced magnetization switching.
    [Show full text]
  • Topological Materials∗ New Quantum Phases of Matter
    GENERAL ARTICLE Topological Materials∗ New Quantum Phases of Matter Vishal Bhardwaj and Ratnamala Chatterjee In this article, we provide an overview of the basic concepts of novel topological materials. This new class of materials developed by combining the Weyl/Dirac fermionic electron states and magnetism, provide a materials-science platform to test predictions of the laws of topological physics. Owing to their dissipationless transport, these materials hold high promises for technological applications in quantum comput- Vishal Bhardwaj is a PhD ing and spintronics devices. student in Department of physics IIT Delhi. He works on thin film growth and experimental Introduction characterization of half Heusler alloys based In condensed matter physics, phase transitions in materials are topologically non-trivial generally understood using Landau’s theory of symmetry break- semi-metals. ing. For example, phase transformation from gas (high symmet- Prof. Ratnamala Chatterjee ric) to solid (less symmetric) involves breaking of translational is currently a Professor and symmetry. Another example is ferromagnetic materials that spon- Head, Physics Department at I.I.T Delhi. Areas of her taneously break the spin rotation symmetry during a phase change research interests are: novel from paramagnetic state to ferromagnetic state below its Curie magnetic & functional temperature. materials including topological insulators, However, with the discovery of quantum Hall effect in 2D sys- Heusler alloys for shape tems, it was realized that the conducting to insulating phase tran- memory, magnetocaloric & spintronics applications, sitions observed in Hall conductivity (σxy) do not follow the time- magnetoelectric multiferroic reversal symmetry breaking condition. Thus it was realized that a materials, shape memory in new classification of matter based on the topology of materials is ceramics, and microwave required to understand quantum phase transitions in quantum Hall absorbing materials.
    [Show full text]
  • Quantum Hall Effect on Top and Bottom Surface States of Topological
    Quantum Hall Effect on Top and Bottom Surface States of Topological Insulator (Bi1−xSbx)2Te 3 Films R. Yoshimi1*, A. Tsukazaki2,3, Y. Kozuka1, J. Falson1, K. S. Takahashi4, J. G. Checkelsky1, N. Nagaosa1,4, M. Kawasaki1,4 and Y. Tokura1,4 1 Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan 2 Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan 3 PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075, Japan ４ RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan. * Corresponding author: [email protected] 1 The three-dimensional (3D) topological insulator (TI) is a novel state of matter as characterized by two-dimensional (2D) metallic Dirac states on its surface1-4. Bi-based chalcogenides such as Bi2Se3, Bi2Te 3, Sb2Te 3 and their combined/mixed compounds like Bi2Se2Te and (Bi1−xSbx)2Te 3 are typical members of 3D-TIs which have been intensively studied in forms of bulk single crystals and thin films to verify the topological nature of the surface states5-12. Here, we report the realization of the Quantum Hall effect (QHE) on the surface Dirac states in (Bi1−xSbx)2Te 3 films (x = 0.84 and 0.88). With electrostatic gate-tuning of the Fermi level in the bulk band gap under magnetic fields, the quantum Hall states with filling factor ν = ± 1 are resolved with 2 quantized Hall resistance of Ryx = ± h/e and zero longitudinal resistance, owing to chiral edge modes at top/bottom surface Dirac states.
    [Show full text]
  • Topological Electronic Structure and Intrinsic Magnetization in Mnbi4te7: a Bi2te3 Derivative with a Periodic Mn Sublattice
    PHYSICAL REVIEW X 9, 041065 (2019) Topological Electronic Structure and Intrinsic Magnetization in MnBi4Te7: A Bi2Te3 Derivative with a Periodic Mn Sublattice Raphael C. Vidal,1,2,* Alexander Zeugner,3,* Jorge I. Facio,4,* Rajyavardhan Ray,4 M. Hossein Haghighi,4 Anja U. B. Wolter,4,2 Laura T. Corredor Bohorquez,4 Federico Caglieris,4 Simon Moser,2,5,6 Tim Figgemeier,1,2 Thiago R. F. Peixoto ,1,2 Hari Babu Vasili,7 Manuel Valvidares,7 Sungwon Jung,8 Cephise Cacho,8 Alexey Alfonsov,4 Kavita Mehlawat,4,2 Vladislav Kataev ,4 Christian Hess ,4,2 Manuel Richter,4,9 Bernd Büchner,4,2,10 † ‡ Jeroen van den Brink,4,2,10 Michael Ruck,3,2,11 Friedrich Reinert,1,2 Hendrik Bentmann,1,2, and Anna Isaeva 4,2,10, 1Experimental Physics VII, Universität Würzburg, D-97074 Würzburg, Germany 2Würzburg-Dresden Cluster of Excellence ct.qmat, Germany 3Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, D-01062 Dresden, Germany 4Leibniz IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany 5Experimental Physics IV, Universität Würzburg, D-97074 Würzburg, Germany 6Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA 7ALBA Synchrotron Light Source, E-08290 Cerdanyola del Valles, Spain 8Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom 9Dresden Center for Computational Materials Science (DCMS), Technische Universität Dresden, D-01062 Dresden, Germany 10Faculty of Physics, Technische Universität Dresden, D-01062 Dresden, Germany 11Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany (Received 19 June 2019; published 31 December 2019) Combinations of nontrivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect.
    [Show full text]
  • (2020) Time-Crystalline Phases and Period-Doubling Oscillations in One-Dimensional Floquet Topological Insulators
    PHYSICAL REVIEW RESEARCH 2, 043239 (2020) Time-crystalline phases and period-doubling oscillations in one-dimensional Floquet topological insulators Yiming Pan 1,* and Bing Wang2 1Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel 2National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, China (Received 12 October 2019; accepted 9 September 2020; published 16 November 2020) In this work, we report a ubiquitous presence of topological Floquet time crystal (TFTC) in one-dimensional periodically driven systems. The rigidity and realization of spontaneous discrete time-translation symmetry (DTS) breaking in our TFTC model require necessarily coexistence of anomalous topological invariants (0 modes and π modes), instead of the presence of disorders or many-body localization. We found that in a particular frequency range of the underlying drive, the anomalous Floquet phase coexistence between 0 and π modes can produce the period doubling (2T , two cycles of the drive) that breaks the DTS spontaneously, leading to the subharmonic response (ω/2, half the drive frequency). The rigid period-2T oscillation is topologically protected against perturbations due to both nontrivially opening of 0 and π gaps in the quasienergy spectrum, thus, as a result, can be viewed as a specific “Rabi oscillation” between two Floquet eigenstates with certain quasienergy splitting π/T . Our modeling of the time-crystalline “ground state” can be easily realized in experimental platforms such as topological photonics and ultracold fields. Also, our work can bring significant interest to explore topological phase transition in Floquet systems and to bridge the gap between Floquet topological insulators and photonics, and period-doubled time crystals.
    [Show full text]