Breakdown of weak-field magnetotransport at a metallic quantum critical point

TL;DR

This paper investigates how quantum criticality in metals causes breakdowns in traditional weak-field magnetotransport calculations, revealing discontinuities and the limits of existing theoretical approaches.

Contribution

It demonstrates the failure of the weak-field Jones-Zener expansion at a metallic quantum critical point with a density-wave transition, highlighting new physics beyond standard assumptions.

Findings

Discontinuities in transport coefficients at zero temperature near the critical point.

Breakdown of the weak field approximation due to quantum critical fluctuations.

Discontinuities are rounded by potential scattering and magnetic breakdown within a specific window.

Abstract

We show how the collapse of an energy scale in a quantum critical metal can lead to physics beyond the weak-field limit usually used to compute transport quantities. For a density-wave transition we show that the presence of a finite magnetic field at the critical point leads to discontinuities in the transport coefficients as temperature tends to zero. The origin of these discontinuities lies in the breakdown of the weak field Jones-Zener expansion which has previously been used to argue that magneto-transport coefficients are continuous at simple quantum critical points. The presence of potential scattering and magnetic breakdown rounds the discontinuities over a window determined by tau Delta < 1 where Delta is the order parameter and tau is the quasiparticle elastic lifetime.