Giant magnetochiral anisotropy from quantum confined surface states of topological insulator nanowires

TL;DR

This paper predicts and experimentally confirms a giant magnetochiral anisotropy effect in topological insulator nanowires, achieving the largest rectification coefficient ever reported, by breaking inversion symmetry with an applied gate voltage.

Contribution

The study introduces a method to induce giant MCA in topological insulator nanowires through symmetry breaking, significantly surpassing previous rectification coefficients.

Findings

Experimental MCA coefficient of ~100,000 A^{-1} T^{-1} achieved.

Theoretical prediction of giant MCA due to inversion symmetry breaking.

Confirmation of theory through experiments on TI nanowires.

Abstract

Wireless technology relies on the conversion of alternating electromagnetic fields to direct currents, a process known as rectification. While rectifiers are normally based on semiconductor diodes, quantum mechanical non-reciprocal transport effects that enable highly controllable rectification have recently been discovered. One such effect is magnetochiral anisotropy (MCA), where the resistance of a material or a device depends on both the direction of current flow and an applied magnetic field. However, the size of rectification possible due to MCA is usually extremely small, because MCA relies on inversion symmetry breaking leading to the manifestation of spin-orbit coupling, which is a relativistic effect. In typical materials the rectification coefficient $\gamma$ due to MCA is usually $|\gamma| \lesssim 1$ ${\rm A^{-1} T^{-1}}$ and the maximum values reported so far are $|\gamma| \sim 100$ ${\rm A^{-1} T^{-1}}$ in carbon nanotubes and ZrTe$_5$. Here, to overcome this limitation, we artificially break inversion symmetry via an applied gate voltage in thin topological insulator (TI) nanowire heterostructures and theoretically predict that such a symmetry breaking can lead to a giant MCA effect. Our prediction is confirmed via experiments on thin bulk-insulating (Bi$_{1-x}$Sb$_{x}$)$_2$Te$_3$ TI nanowires, in which we observe an MCA consistent with theory and $|\gamma| \sim 100000$ ${\rm A^{-1} T^{-1}}$, the largest ever reported MCA rectification coefficient in a normal conductor.