1
|
Kealhofer DA, Kealhofer R, Ohara D, Pardue TN, Stemmer S. Controlling and visualizing Dirac physics in topological semimetal heterostructures. SCIENCE ADVANCES 2022; 8:eabn4479. [PMID: 35857456 PMCID: PMC9269884 DOI: 10.1126/sciadv.abn4479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
A bulk crystal of cadmium arsenide is a three-dimensional Dirac semimetal, but, in a thin film, it can behave like a three-dimensional topological insulator. This tunability provides unique opportunities to manipulate and explore a topological insulator phase. However, an obstacle to engineering such tunability is the subtlety of transport-based discriminants for topological phases. In this work, the quantum capacitance of cadmium arsenide-based heterostructures provides two direct experimental signatures of three-dimensional topological insulator physics: an insulating three-dimensional bulk and a Landau level at zero energy that does not disperse in a magnetic field. We proceed to join our ability to see these fingerprints of the topological surface states with flexibility afforded by our epitaxial heterostructures to demonstrate a route toward controlling the energy of the Dirac nodes on each surface. These results point to new avenues for engineering topological insulators based on cadmium arsenide.
Collapse
|
2
|
Large magnetocapacitance beyond 420% in epitaxial magnetic tunnel junctions with an MgAl2O4 barrier. Sci Rep 2022; 12:7190. [PMID: 35577827 PMCID: PMC9110733 DOI: 10.1038/s41598-022-11545-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 04/18/2022] [Indexed: 11/30/2022] Open
Abstract
Magnetocapacitance (MC) effect has been observed in systems where both symmetries of time-reversal and space-inversion are broken, for examples, in multiferroic materials and spintronic devices. The effect has received increasing attention due to its interesting physics and the prospect of applications. Recently, a large tunnel magnetocapacitance (TMC) of 332% at room temperature was reported using MgO-based (001)-textured magnetic tunnel junctions (MTJs). Here, we report further enhancement in TMC beyond 420% at room temperature using epitaxial MTJs with an MgAl2O4(001) barrier with a cation-disordered spinel structure. This large TMC is partially caused by the high effective tunneling spin polarization, resulted from the excellent lattice matching between the Fe electrodes and the MgAl2O4 barrier. The epitaxial nature of this MTJ system sports an enhanced spin-dependent coherent tunneling effect. Among other factors leading to the large TMC are the appearance of the spin capacitance, the large barrier height, and the suppression of spin flipping through the MgAl2O4 barrier. We explain the observed TMC by the Debye-Fröhlich modelled calculation incorporating Zhang-sigmoid formula, parabolic barrier approximation, and spin-dependent drift diffusion model. Furthermore, we predict a 1000% TMC in MTJs with a spin polarization of 0.8. These experimental and theoretical findings provide a deeper understanding on the intrinsic mechanism of the TMC effect. New applications based on large TMC may become possible in spintronics, such as multi-value memories, spin logic devices, magnetic sensors, and neuromorphic computing.
Collapse
|
3
|
Thermoelectric Transport in a Three-Dimensional HgTe Topological Insulator. NANOMATERIALS 2021; 11:nano11123364. [PMID: 34947713 PMCID: PMC8707520 DOI: 10.3390/nano11123364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Revised: 12/06/2021] [Accepted: 12/07/2021] [Indexed: 12/02/2022]
Abstract
The thermoelectric response of 80 nm-thick strained HgTe films of a three-dimensional topological insulator (3D TI) has been studied experimentally. An ambipolar thermopower is observed where the Fermi energy moves from conducting to the valence bulk band. The comparison between theory and experiment shows that the thermopower is mostly due to the phonon drag contribution. In the region where the 2D Dirac electrons coexist with bulk hole states, the Seebeck coefficient is modified due to 2D electron–3D hole scattering.
Collapse
|
4
|
Balasubramanian K. Quantum capacitance of coupled two-dimensional electron gases. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:28LT01. [PMID: 33588395 DOI: 10.1088/1361-648x/abe64f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
Quantum capacitance effect is observed in nanostructured material stacks with quantum limited density of states. In contrast to conventional structures where two-dimensional electron gases (2DEG) with reduced density of states interact with a metal plate, here we explore the quantum capacitance effect in a unique structure formed by two 2DEG in a graphene sheet and AlGaN/GaN quantum well. The total capacitance of the structure depends non-linearly on the applied potential and the linear density of states in graphene leads to enhanced electric field leakage into the substrate causing a dramatic 50% drop in the overall capacitance at low bias potentials. We show theoretical projections of the quantum capacitance effect in the proposed device stack, fabricate the structure and provide experimental verification of the calculated values at various temperatures and applied potentials. The wide swing in the total capacitance is sensitive to the chemical potential of the graphene sheet and has multiple applications in molecular sensing, electro-optics, and fundamental investigations.
Collapse
Affiliation(s)
- Krishna Balasubramanian
- Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| |
Collapse
|
5
|
Wang J, Gorini C, Richter K, Wang Z, Ando Y, Weiss D. Two-Dimensional-Dirac Surface States and Bulk Gap Probed via Quantum Capacitance in a Three-Dimensional Topological Insulator. NANO LETTERS 2020; 20:8493-8499. [PMID: 33174423 DOI: 10.1021/acs.nanolett.0c02733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
BiSbTeSe2 is a 3D topological insulator (3D-TI) with Dirac type surface states and low bulk carrier density, as donors and acceptors compensate each other. Dominating low-temperature surface transport in this material is heralded by Shubnikov-de Haas oscillations and the quantum Hall effect. Here, we experimentally probe and model the electronic density of states (DOS) in thin layers of BiSbTeSe2 by capacitance experiments both without and in quantizing magnetic fields. By probing the lowest Landau levels, we show that a large fraction of the electrons filled via field effect into the system ends up in (localized) bulk states and appears as a background DOS. The surprisingly strong temperature dependence of such background DOS can be traced back to Coulomb interactions. Our results point at the coexistence and intimate coupling of Dirac surface states with a bulk many-body phase (a Coulomb glass) in 3D-TIs.
Collapse
Affiliation(s)
- Jimin Wang
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Cosimo Gorini
- Institute of Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Klaus Richter
- Institute of Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Zhiwei Wang
- Physics Institute II, University of Cologne, Zülpicher Strasse 77, 50937 Köln, Germany
- Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement, Ministry of Education, School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Yoichi Ando
- Physics Institute II, University of Cologne, Zülpicher Strasse 77, 50937 Köln, Germany
| | - Dieter Weiss
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| |
Collapse
|
6
|
Anomalous Decay of Quantum Resistance Oscillations of 2D Helical Electrons in Magnetic Field. Sci Rep 2020; 10:7875. [PMID: 32398662 PMCID: PMC7217846 DOI: 10.1038/s41598-020-64385-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 04/15/2020] [Indexed: 11/08/2022] Open
Abstract
Shubnikov de Haas resistance oscillations of highly mobile two dimensional helical electrons propagating on a conducting surface of strained HgTe 3D topological insulator are studied in magnetic fields B tilted by angle θ from the normal to the conducting layer. Strong decrease of oscillation amplitude A is observed with the tilt: \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{A}}\sim {\boldsymbol{e}}{\boldsymbol{x}}{\boldsymbol{p}}(\,-\,{\boldsymbol{\xi }}/{\boldsymbol{c}}{\boldsymbol{o}}{\boldsymbol{s}}({\boldsymbol{\theta }}))$$\end{document}A∼exp(−ξ/cos(θ)), where ξ is a constant. Evolution of the oscillations with temperature T shows that the parameter \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{\xi }}$$\end{document}ξ contains two terms: \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${\boldsymbol{\xi }}={{\boldsymbol{\xi }}}_{1}+{{\boldsymbol{\xi }}}_{2}{\boldsymbol{T}}$$\end{document}ξ=ξ1+ξ2T. The temperature independent term, \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${{\boldsymbol{\xi }}}_{{\bf{1}}}$$\end{document}ξ1, signals possible reduction of electron mean free path \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${l}_{q}$$\end{document}lq and/or enhancement of in-homogeneous broadening of the oscillations in magnetic field B. The temperature dependent term, \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${{\boldsymbol{\xi }}}_{{\bf{2}}}{\boldsymbol{T}}$$\end{document}ξ2T, indicates increase of the reciprocal velocity of 2D helical electrons: \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\delta ({v}_{F}^{-1})\sim B$$\end{document}δ(vF−1)∼B suggesting modification of the electron spectrum in magnetic fields. Results are found in good agreement with proposed phenomenological model.
Collapse
|
7
|
Liu P, Ren Y, Zhou X, Xiao X, Zhou G. Probing the anisotropy of Landau levels in phosphorene by magneto-capacitance with a parabolic potential confinement. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:425702. [PMID: 32585645 DOI: 10.1088/1361-648x/aba016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 06/25/2020] [Indexed: 06/11/2023]
Abstract
We theoretically investigate the Landau levels (LLs) and magneto-capacitance (MC) of monolayer black phosphorus under a perpendicular magnetic field, on which a parabolic potential is applied along with the armchair and zigzag directions, respectively. By both analytically perturbative calculation and numerical diagonalization based on an effectivek⋅pHamiltonian, we find that the LLs parabolically depend on the wave vectors and show strong anisotropy as the parabolic potential is applied along with different crystal directions. Specifically, the analytical LLs obtained by perturbative calculation from a decoupled single-band Hamiltonian are in good agreement with the numerical results. Importantly, the LLs are no longer linearly dependent on the magnetic field and level index even in the low energy regime due to the confinement of parabolic potential which repaints the cyclotron orbits. Moreover, the MC spectrum clearly reflects the structure of the LLs and exhibits strong anisotropic oscillating patterns. It can be used to determine the band parameters of phosphorene, i.e., the effective masses and inter-band coupling in the absence of magnetic and electric fields.
Collapse
Affiliation(s)
- Pu Liu
- Department of Physics, Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), and Synergetic Innovation Center for Quantum Effects and Applications of Hunan, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Yi Ren
- Department of Physics, Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), and Synergetic Innovation Center for Quantum Effects and Applications of Hunan, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Xiaoying Zhou
- Department of Physics, Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), and Synergetic Innovation Center for Quantum Effects and Applications of Hunan, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Xianbo Xiao
- School of Computer Science, Jiangxi University of Traditional Chinese Medicine, Nanchang 330004, People's Republic of China
| | - Guanghui Zhou
- Department of Physics, Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), and Synergetic Innovation Center for Quantum Effects and Applications of Hunan, Hunan Normal University, Changsha 410081, People's Republic of China
| |
Collapse
|
8
|
Krishtopenko SS, Antezza M, Teppe F. Hybridization of topological surface states with a flat band. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:165501. [PMID: 31899908 DOI: 10.1088/1361-648x/ab6741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We address the problem of hybridization between topological surface states and a non-topological flat bulk band. Our model, being a mixture of three-dimensional Bernevig-Hughes-Zhang and two-dimensional pseudospin-1 Hamiltonian, allows explicit treatment of the topological surface state evolution by continuously changing the hybridization between the inverted bands and an additional 'parasitic' flat band in the bulk. We show that the hybridization with a flat band lying below the edge of the conduction band converts the initial Dirac-like surface states into a branch below and one above the flat band. Our results univocally demonstrate that the upper branch of the topological surface states is formed by Dyakonov-Khaetskii surface states, known for HgTe since the 1980s. Additionally we explore an evolution of the surface states and the arising of Fermi arcs in Dirac semimetals when the flat band crosses the conduction band.
Collapse
Affiliation(s)
- Sergey S Krishtopenko
- Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, F-34095 Montpellier, France
| | | | | |
Collapse
|
9
|
Dartiailh MC, Hartinger S, Gourmelon A, Bendias K, Bartolomei H, Kamata H, Berroir JM, Fève G, Plaçais B, Lunczer L, Schlereth R, Buhmann H, Molenkamp LW, Bocquillon E. Dynamical Separation of Bulk and Edge Transport in HgTe-Based 2D Topological Insulators. PHYSICAL REVIEW LETTERS 2020; 124:076802. [PMID: 32142329 DOI: 10.1103/physrevlett.124.076802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 01/13/2020] [Indexed: 06/10/2023]
Abstract
Topological effects in edge states are clearly visible on short lengths only, thus largely impeding their studies. On larger distances, one may be able to dynamically enhance topological signatures by exploiting the high mobility of edge states with respect to bulk carriers. Our work on microwave spectroscopy highlights the response of the edges which host very mobile carriers, while bulk carriers are drastically slowed down in the gap. Though the edges are denser than expected, we establish that charge relaxation occurs on short timescales and suggest that edge states can be addressed selectively on timescales over which bulk carriers are frozen.
Collapse
Affiliation(s)
- Matthieu C Dartiailh
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Simon Hartinger
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Alexandre Gourmelon
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Kalle Bendias
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Hugo Bartolomei
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Hiroshi Kamata
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Jean-Marc Berroir
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Gwendal Fève
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Bernard Plaçais
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| | - Lukas Lunczer
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Raimund Schlereth
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Hartmut Buhmann
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Laurens W Molenkamp
- Physikalisches Institut (EP3), Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, Universität Würzburg, D-97074 Würzburg, Germany
| | - Erwann Bocquillon
- Laboratoire de Physique de l'École Normale Supérieure, ENS, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
| |
Collapse
|
10
|
Chong SK, Tsuchikawa R, Harmer J, Sparks TD, Deshpande VV. Landau Levels of Topologically-Protected Surface States Probed by Dual-Gated Quantum Capacitance. ACS NANO 2020; 14:1158-1165. [PMID: 31833755 DOI: 10.1021/acsnano.9b09192] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Spectroscopy of discrete Landau levels (LLs) in bulk-insulating three-dimensional topological insulators (3D TIs) in perpendicular magnetic field characterizes the Dirac nature of their surface states. Despite a number of studies demonstrating the quantum Hall effect (QHE) of topological surface states, quantitative evaluation of the LL energies, which serve as fundamental electronic quantities for study of the quantum states, is still limited. In this work, we explore the density of states of LLs by measuring quantum capacitance (CQ) in a truly bulk insulating 3D TI via a van der Waals heterostructure configuration. By applying dual-gate voltages, we access the individual surface states' LLs and extract their chemical potentials to quantify the LL spacings of each surface. We evaluate the LLs' energies at two distinguished QH states, namely, dissipationless (ν = ±1) and dissipative (ν = 0) states in the 3D TI.
Collapse
Affiliation(s)
- Su Kong Chong
- Department of Physics and Astronomy , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Ryuichi Tsuchikawa
- Department of Physics and Astronomy , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Jared Harmer
- Department of Physics and Astronomy , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Taylor D Sparks
- Department of Materials Science and Engineering , University of Utah , Salt Lake City , Utah 84112 , United States
| | - Vikram V Deshpande
- Department of Physics and Astronomy , University of Utah , Salt Lake City , Utah 84112 , United States
| |
Collapse
|
11
|
Ballistic geometric resistance resonances in a single surface of a topological insulator. Nat Commun 2017; 8:2023. [PMID: 29222407 PMCID: PMC5722899 DOI: 10.1038/s41467-017-01684-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/09/2017] [Indexed: 12/03/2022] Open
Abstract
Transport in topological matter has shown a variety of novel phenomena over the past decade. Although numerous transport studies have been conducted on three-dimensional topological insulators (TIs), study of ballistic motion and thus exploration of potential landscapes on a hundred nanometer scale is for the prevalent TI materials almost impossible due to their low carrier mobility. Therefore, it is unknown whether helical Dirac electrons in TIs, bound to interfaces between topologically distinct materials, can be manipulated on the nanometer scale by local gates or locally etched regions. Here we impose a submicron periodic potential onto a single surface of Dirac electrons in high-mobility strained mercury telluride (HgTe), which is a strong TI. Pronounced geometric resistance resonances constitute the clear-cut observation of a ballistic effect in three-dimensional TIs. Ballistic motion on nanometer scale of topological surface states has rarely been studied. Here, Maier et al. report pronounced geometric resistance resonances of high-mobility Dirac electrons in strained HgTe, suggesting a ballistic effect in three-dimensional topological insulators.
Collapse
|
12
|
Bisri SZ, Shimizu S, Nakano M, Iwasa Y. Endeavor of Iontronics: From Fundamentals to Applications of Ion-Controlled Electronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1607054. [PMID: 28582588 DOI: 10.1002/adma.201607054] [Citation(s) in RCA: 177] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 02/16/2017] [Indexed: 05/28/2023]
Abstract
Iontronics is a newly emerging interdisciplinary concept which bridges electronics and ionics, covering electrochemistry, solid-state physics, electronic engineering, and biological sciences. The recent developments of electronic devices are highlighted, based on electric double layers formed at the interface between ionic conductors (but electronically insulators) and various electronic conductors including organics and inorganics (oxides, chalcogenide, and carbon-based materials). Particular attention is devoted to electric-double-layer transistors (EDLTs), which are producing a significant impact, particularly in electrical control of phase transitions, including superconductivity, which has been difficult or impossible in conventional all-solid-state electronic devices. Besides that, the current state of the art and the future challenges of iontronics are also reviewed for many applications, including flexible electronics, healthcare-related devices, and energy harvesting.
Collapse
Affiliation(s)
- Satria Zulkarnaen Bisri
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Sunao Shimizu
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Masaki Nakano
- Quantum Phase Electronic Center (QPEC) and Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yoshihiro Iwasa
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
- Quantum Phase Electronic Center (QPEC) and Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| |
Collapse
|