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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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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, Chang JT, Chuang PY, Tsai MC, Peng YW, Lee MK, Cheng CM, Huang JCA. Epitaxial Growth and Structural Characterizations of MnBi 2Te 4 Thin Films in Nanoscale. NANOMATERIALS 2021; 11:nano11123322. [PMID: 34947669 PMCID: PMC8703544 DOI: 10.3390/nano11123322] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/02/2021] [Accepted: 12/02/2021] [Indexed: 11/30/2022]
Abstract
The intrinsic magnetic topological insulator MnBi2Te4 has attracted much attention due to its special magnetic and topological properties. To date, most reports have focused on bulk or flake samples. For material integration and device applications, the epitaxial growth of MnBi2Te4 film in nanoscale is more important but challenging. Here, we report the growth of self-regulated MnBi2Te4 films by the molecular beam epitaxy. By tuning the substrate temperature to the optimal temperature for the growth surface, the stoichiometry of MnBi2Te4 becomes sensitive to the Mn/Bi flux ratio. Excessive and deficient Mn resulted in the formation of a MnTe and Bi2Te3 phase, respectively. The magnetic measurement of the 7 SL MnBi2Te4 film probed by the superconducting quantum interference device (SQUID) shows that the antiferromagnetic order occurring at the Néel temperature 22 K is accompanied by an anomalous magnetic hysteresis loop along the c-axis. The band structure measured by angle-resolved photoemission spectroscopy (ARPES) at 80 K reveals a Dirac-like surface state, which indicates that MnBi2Te4 has topological insulator properties in the paramagnetic phase. Our work demonstrates the key growth parameters for the design and optimization of the synthesis of nanoscale MnBi2Te4 films, which are of great significance for fundamental research and device applications involving antiferromagnetic topological insulators.
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Affiliation(s)
- Shu-Hsuan Su
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
| | - Jen-Te Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
| | - Pei-Yu Chuang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
| | - Ming-Chieh Tsai
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
| | - Yu-Wei Peng
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
| | - Min Kai Lee
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
| | - Cheng-Maw Cheng
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106335, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
- Correspondence: (C.-M.C.); (J.-C.A.H.)
| | - Jung-Chung Andrew Huang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan; (S.-H.S.); (J.-T.C.); (P.-Y.C.); (M.-C.T.); (Y.-W.P.); (M.K.L.)
- Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei 10601, Taiwan
- Department of Applied Physics, National University of Kaohsiung, Kaohsiung, 811, Taiwan
- Correspondence: (C.-M.C.); (J.-C.A.H.)
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