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Sheverdyaeva PM, Hogan C, Bihlmayer G, Fujii J, Vobornik I, Jugovac M, Kundu AK, Gardonio S, Benher ZR, Santo GD, Gonzalez S, Petaccia L, Carbone C, Moras P. Giant and Tunable Out-of-Plane Spin Polarization of Topological Antimonene. NANO LETTERS 2023; 23:6277-6283. [PMID: 37459226 PMCID: PMC10375579 DOI: 10.1021/acs.nanolett.3c00153] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Topological insulators are bulk insulators with metallic and fully spin-polarized surface states displaying Dirac-like band dispersion. Due to spin-momentum locking, these topological surface states (TSSs) have a predominant in-plane spin polarization in the bulk fundamental gap. Here, we show by spin-resolved photoemission spectroscopy that the TSS of a topological insulator interfaced with an antimonene bilayer exhibits nearly full out-of-plane spin polarization within the substrate gap. We connect this phenomenon to a symmetry-protected band crossing of the spin-polarized surface states. The nearly full out-of-plane spin polarization of the TSS occurs along a continuous path in the energy-momentum space, and the spin polarization within the gap can be reversibly tuned from nearly full out-of-plane to nearly full in-plane by electron doping. These findings pave the way to advanced spintronics applications that exploit the giant out-of-plane spin polarization of TSSs.
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Affiliation(s)
- Polina M Sheverdyaeva
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Conor Hogan
- Istituto di Struttura della Materia-CNR (ISM-CNR), Via del Fosso del Cavaliere 100, 00133 Roma, Italy
- Dipartimento di Fisica, Università di Roma "Tor Vergata", Via della Ricerca Scientifica 1, 00133 Roma, Italy
| | - Gustav Bihlmayer
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - Jun Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Ivana Vobornik
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Matteo Jugovac
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149 Trieste, Italy
- Peter Grünberg Institut PGI, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Asish K Kundu
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149 Trieste, Italy
- International Center for Theoretical Physics (ICTP), Trieste, 34151, Italy
| | - Sandra Gardonio
- Materials Research Laboratory, University of Nova Gorica, Vipavska 11c, Ajdovščina 5270, Slovenia
| | - Zipporah Rini Benher
- Materials Research Laboratory, University of Nova Gorica, Vipavska 11c, Ajdovščina 5270, Slovenia
| | - Giovanni Di Santo
- Elettra - Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Sara Gonzalez
- Elettra - Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Luca Petaccia
- Elettra - Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Carlo Carbone
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Paolo Moras
- Istituto di Struttura della Materia-CNR (ISM-CNR), Strada Statale 14 km 163.5, 34149 Trieste, Italy
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Liu B, Wagner T, Enzner S, Eck P, Kamp M, Sangiovanni G, Claessen R. Moiré Pattern Formation in Epitaxial Growth on a Covalent Substrate: Sb on InSb(111)A. NANO LETTERS 2023; 23:3189-3195. [PMID: 37027539 DOI: 10.1021/acs.nanolett.2c04974] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Structural moiré superstructures arising from two competing lattices may lead to unexpected electronic behavior. Sb is predicted to show thickness-dependent topological properties, providing potential applications for low-energy-consuming electronic devices. Here we successfully synthesize ultrathin Sb films on semi-insulating InSb(111)A. Despite the covalent nature of the substrate, which has dangling bonds on the surface, we prove by scanning transmission electron microscopy that the first layer of Sb atoms grows in an unstrained manner. Rather than compensating for the lattice mismatch of -6.4% by structural modifications, the Sb films form a pronounced moiré pattern as we evidence by scanning tunneling microscopy. Our model calculations assign the moiré pattern to a periodic surface corrugation. In agreement with theoretical predictions, irrespective of the moiré modulation, the topological surface state known on a thick Sb film is experimentally confirmed to persist down to small film thicknesses, and the Dirac point shifts toward lower binding energies with a decrease in Sb thickness.
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Affiliation(s)
- Bing Liu
- Physikalisches Institut, Universität Würzburg, D-97074 Würzburg, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, D-97074 Würzburg, Germany
| | - Tim Wagner
- Physikalisches Institut, Universität Würzburg, D-97074 Würzburg, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, D-97074 Würzburg, Germany
| | - Stefan Enzner
- Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, D-97074 Würzburg, Germany
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, D-97074 Würzburg, Germany
| | - Philipp Eck
- Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, D-97074 Würzburg, Germany
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, D-97074 Würzburg, Germany
| | - Martin Kamp
- Physikalisches Institut, Universität Würzburg, D-97074 Würzburg, Germany
| | - Giorgio Sangiovanni
- Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, D-97074 Würzburg, Germany
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, D-97074 Würzburg, Germany
| | - Ralph Claessen
- Physikalisches Institut, Universität Würzburg, D-97074 Würzburg, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, D-97074 Würzburg, Germany
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Li Y, Bowers JW, Hlevyack JA, Lin MK, Chiang TC. Emergent and Tunable Topological Surface States in Complementary Sb/Bi 2Te 3 and Bi 2Te 3/Sb Thin-Film Heterostructures. ACS NANO 2022; 16:9953-9959. [PMID: 35699943 PMCID: PMC9245572 DOI: 10.1021/acsnano.2c04639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 06/09/2022] [Indexed: 06/15/2023]
Abstract
Epitaxial thin-film heterostructures offer a versatile platform for realizing topological surface states (TSSs) that may be emergent and/or tunable by tailoring the atomic layering in the heterostructures. Here, as an experimental demonstration, Sb and Bi2Te3 thin films with closely matched in-plane lattice constants are chosen to form two complementary heterostructures: Sb overlayers on Bi2Te3 (Sb/Bi2Te3) and Bi2Te3 overlayers on Sb (Bi2Te3/Sb), with the overlayer thickness as a tuning parameter. In the bulk form, Sb (a semimetal) and Bi2Te3 (an insulator) both host TSSs with the same topological order but substantially different decay lengths and dispersions, whereas ultrathin Sb and Bi2Te3 films by themselves are fully gapped trivial insulators. Angle-resolved photoemission band mappings, aided by theoretical calculations, confirm the formation of emergent TSSs in both heterostructures. The energy position of the topological Dirac point varies as a function of overlayer thickness, but the variation is non-monotonic, indicating nontrivial effects in the formation of topological heterostructure systems. The results illustrate the rich physics of engineered composite topological systems that may be exploited for nanoscale spintronics applications.
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Affiliation(s)
- Yao Li
- Department
of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Frederick
Seitz Materials Research Laboratory, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - John W. Bowers
- Department
of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Frederick
Seitz Materials Research Laboratory, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Joseph A. Hlevyack
- Department
of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Frederick
Seitz Materials Research Laboratory, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Meng-Kai Lin
- Department
of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Frederick
Seitz Materials Research Laboratory, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Department
of Physics, National Central University, Taoyuan 32001, Taiwan
| | - Tai-Chang Chiang
- Department
of Physics, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
- Frederick
Seitz Materials Research Laboratory, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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Su SH, Chuang PY, Chen HY, Weng SC, Chen WC, Tsuei KD, Lee CK, Yu SH, Chou MMC, Tu LW, Jeng HT, Tu CM, Luo CW, Cheng CM, Chang TR, Huang JCA. Topological Proximity-Induced Dirac Fermion in Two-Dimensional Antimonene. ACS NANO 2021; 15:15085-15095. [PMID: 34435764 DOI: 10.1021/acsnano.1c05454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Antimonene is a promising two-dimensional (2D) material that is calculated to have a significant fundamental bandgap usable for advanced applications such as field-effect transistors, photoelectric devices, and the quantum-spin Hall (QSH) state. Herein, we demonstrate a phenomenon termed topological proximity effect, which occurs between a 2D material and a three-dimensional (3D) topological insulator (TI). We provide strong evidence derived from hydrogen etching on Sb2Te3 that large-area and well-ordered antimonene presents a 2D topological state. Delicate analysis with a scanning tunneling microscope of the evolutionary intermediates reveals that hydrogen etching on Sb2Te3 resulted in the formation of a large area of antimonene with a buckled structure. A topological state formed in the antimonene/Sb2Te3 heterostructure was confirmed with angle-resolved photoemission spectra and density-functional theory calculations; in particular, the Dirac point was located almost at the Fermi level. The results reveal that Dirac fermions are indeed realized at the interface of a 2D normal insulator (NI) and a 3D TI as a result of strong hybridization between antimonene and Sb2Te3. Our work demonstrates that the position of the Dirac point and the shape of the Dirac surface state can be tuned by varying the energy position of the NI valence band, which modifies the direction of the spin texture of Sb-BL/Sb2Te3 via varying the Fermi level. This topological phase in 2D-material engineering has generated a paradigm in that the topological proximity effect at the NI/TI interface has been realized, which demonstrates a way to create QSH systems in 2D-material TI heterostructures.
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Affiliation(s)
- Shu Hsuan Su
- Department of Physics, National Cheng Kung University, Taiwan 701, Taiwan
| | - Pei-Yu Chuang
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
| | - Hsin-Yu Chen
- Department of Physics, National Cheng Kung University, Taiwan 701, Taiwan
| | - Shih-Chang Weng
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
| | - Wei-Chuan Chen
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
| | - Ku-Ding Tsuei
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
| | - Chao-Kuei Lee
- Department of Photonics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Research Center for Applied Sciences, Academia Sinica, 187 Academia Road, Taipei 11529, Taiwan
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Shih-Hsun Yu
- Department of Materials and Optoelectronics Science, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Mitch M-C Chou
- Department of Materials and Optoelectronics Science, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Li-Wei Tu
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Horng-Tay Jeng
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
- Physics Division, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Chien-Ming Tu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
| | - Chih-Wei Luo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
- Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106335, Taiwan
| | - Tay-Rong Chang
- Department of Physics, National Cheng Kung University, Taiwan 701, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), Tainan 701, Taiwan
- Physics Division, National Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan
| | - Jung-Chun Andrew Huang
- Department of Physics, National Cheng Kung University, Taiwan 701, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
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Kundu AK, Gu G, Valla T. Quantum Size Effects, Multiple Dirac Cones, and Edge States in Ultrathin Bi(110) Films. ACS APPLIED MATERIALS & INTERFACES 2021; 13:33627-33634. [PMID: 34232636 DOI: 10.1021/acsami.1c06821] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The presence of inherently strong spin-orbit coupling in bismuth, its unique layer-dependent band topology and high carrier mobility make it an interesting system for both fundamental studies and applications. Theoretically, it has been suggested that strong quantum size effects should be present in the Bi(110) films, with the possibility of Dirac Fermion states in the odd-bilayer (BL) films, originating from dangling pz orbitals and quantum-spin hall (QSH) states in the even-bilayer films. However, the experimental verification of these claims has been lacking. Here, we study the electronic structure of Bi(110) films grown on a high-Tc superconductor, Bi2Sr2CaCu2O8+δ (Bi2212) using angle-resolved photoemission spectroscopy (ARPES). We observe an oscillatory behavior of electronic structure with the film thickness and identify the Dirac-states in the odd-bilayer films, consistent with the theoretical predictions. In the even-bilayer films, we find another Dirac state that was predicted to play a crucial role in the QSH effect. In the low thickness limit, we observe several extremely one-dimensional states, probably originating from the edge-states of Bi(110) islands. Our results provide a much needed experimental insight into the electronic and structural properties of Bi(110) films.
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Affiliation(s)
- Asish K Kundu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Tonica Valla
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
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Evolution of Topological Surface States Following Sb Layer Adsorption on Bi 2Se 3. MATERIALS 2021; 14:ma14071763. [PMID: 33918428 PMCID: PMC8061775 DOI: 10.3390/ma14071763] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 03/29/2021] [Accepted: 03/31/2021] [Indexed: 01/28/2023]
Abstract
Thin antimony layers adsorbed on bismuth selenide (Bi2Se3) present an exciting topological insulator system. Much recent effort has been made to understand the synthesis and electronic properties of the heterostructure, particularly the migration of the topological surface states under adsorption. However, the intertwinement of the topological surface states of the pristine Bi2Se3 substrate with the Sb adlayer remains unclear. In this theoretical work, we apply density functional theory (DFT) to model heterostructures of single and double atomic layers of Sb on a bismuth selenide substrate. We thereby discuss established and alternative structural models, as well as the hybridization of topological surface states with the Sb states. Concerning the geometry, we reveal the possibility of structures with inverted Sb layers which are energetically close to the established ones. The formation energy differences are below 10 meV/atom. Concerning the hybridization, we trace the band structure evolution as a function of the adlayer-substrate distance. By following changes in the connection between the Kramers pairs, we extract a series of topological phase transitions. This allows us to explain the origin of the complex band structure, and ultimately complete our knowledge about this peculiar system.
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