Affiliation
University of Basel
Title of work
Majorana bound states and giant magnetochiral anisotropy in topological insulator nanowires
Abstract
We consider a three-dimensional topological insulator (TI) nanowire and show that auniform chemical potential across the cross-section of the nanowire lifts the degeneracy between two one-dimensional surface state subbands. Such a non- uniformity in chemical potential can be induced, for example, by gating [1] or the induced potential at the interface to a superconductor [2].
First, we show that a magnetic field parallel to the nanowire breaks time-reversal symmetry and, primarily due to orbital effects, lifts the Kramers degeneracy at zero- momentum. As a result, when brought into proximity with an s-wave superconductor, Majorana bound states (MBSs), localised at the ends of the TI nanowire, emerge and are present for an exceptionally large region of parameter space in realistic systems[1,2]. Unlike in previous proposals, these MBSs occur without the requirement of a vortex in the pairing potential, representing a significant simplification for experiments.
We also predict that, due to the subband splitting induce by a non-uniform potential, a magnetic field applied perpendicular to the TI nanowire axis should result in a large nonreciprocity of resistivity, an effect known as magnetochiral anisotropy. Our result is confirmed by experiments on thin (Bi1-xSbx)2Te3 nanowires in which we observe the largest ever reported MCA rectification coefficient in a normal conductor [3].
Our results open a simple pathway to the realisation of MBSs in TI nanowires and show many of the ingredients necessary are already realised in current devices.
References
[1] HF Legg, D Loss, J Klinovaja, Majorana bound states in topological insulators without a vortex, PRB 104, 165405 (2021)
[2] HF Legg, D Loss, J Klinovaja, Metallization and proximity superconductivity in topological insulator nanowires, PRB 105, 155413 (2022)
[3] HF Legg, M Rößler, F Münning, D Fan, O Breunig, A Bliesener, G Lippertz, A Uday, AA Taskin, D Loss, J Klinovaja, Y Ando, Giant magnetochiral anisotropy from quantum confined surface states of topological insulator nanowires, Nat. Nanotech. (May 2022)