Quantum geometry and the electric magnetochiral anisotropy in noncentrosymmetric polar media

TL;DR

This paper reveals that quantum geometry, specifically the quantum metric, underpins the electric magnetochiral anisotropy in noncentrosymmetric polar media, and demonstrates control of rectification effects via external parameters, verified through experiments on 2D tellurium.

Contribution

It establishes the role of quantum metric and large Born effective charges in the electric magnetochiral anisotropy and predicts a universal scaling law verified experimentally.

Findings

Quantum metric influences magnetochiral anisotropy.

Universal scaling law $ ightarrow \, ext{γ}^{ ext{±}}(V) \, ext{scales as} \, V^{-5/2}$.

Experimental verification on 2D tellurium films.

Abstract

The electric magnetochiral anisotropy is a nonreciprocal phenomenon accessible via second harmonic transport in noncentrosymmetric, time-reversal invariant materials, in which the rectification of current, ${\bf I}$, can be controlled by an external magnetic field, ${\bf B}$. Quantum geometry, which characterizes the topology of Bloch electrons in a Hilbert space, provides a powerful description of the nonlinear dynamics in topological materials. Here, we demonstrate that the electric magnetochiral anisotropy in noncentrosymmetric polar media owes its existence to the quantum metric, arising from the spin-orbit coupling, and to large Born effective charges. In this context, the reciprocal magnetoresistance $\beta{\bf B}^2$ is modified to $R( I,P,B)=R_0[1+\beta B^2 + \gamma^{\pm}{\bf I}\cdot({\bf P}\times{\bf B})]$, where the chirality dependent $\gamma^{\pm}$ is determined by the quantum metric dipole and the polarization ${\bf P}$. We predict a universal scaling $\gamma^{\pm}(V)\sim V^{-5/2}$ which we verified by phase sensitive, second harmonic transport measurements on hydrothermally grown 2D tellurium films under applied gate voltage, $V$. The control of rectification by varying ${\bf I}$, ${\bf P}$, ${\bf B}$, and $V$, demonstrated in this work, opens up new avenues for the building of ultra-scaled CMOS circuits.