Berry phase effects on the transverse conductivity of Fermi surfaces and their detection via spin qubit noise magnetometry

TL;DR

This paper investigates how Berry phases influence the transverse conductivity in 2D Dirac systems like graphene, revealing universal behavior at long wavelengths and distinctive wave-vector dependence near the Fermi surface, detectable via spin qubit noise magnetometry.

Contribution

It demonstrates that Berry phases do not affect the universal transverse conductivity at long wavelengths but cause notable deviations at wave-vectors near the Fermi radius in Dirac systems.

Findings

Universal transverse conductivity determined by Fermi surface curvature

Distinct wave-vector dependence in Dirac systems including divergences and oscillations

Proposed detection method using spin qubit relaxation times

Abstract

The quasi-static transverse conductivity of clean Fermi liquids at long wavelengths displays a remarkably universal behaviour: it is determined solely by the radius of curvature of the Fermi surface and does not depend on details such as the quasi-particle mass or their interactions. Here we demonstrate that Berry phases do not alter such universality by directly computing the transverse conductivity of two-dimensional electronic systems with Dirac dispersions, such as those appearing in graphene and its chiral multilayer variants. Interestingly, however, such universality ceases to hold at wave-vectors comparable to the Fermi radius, where Dirac fermions display a vividly distict transverse conductivity relative to parabolic Fermions, with a rich wave-vector dependence that includes divergences, oscillations and zeroes. We discuss how this can be probed by measuring the $T_1$ relaxation time of spin qubits, such as NV centers or nuclear spins, placed near such 2D systems.