Quantum critical magneto-transport at a continuous metal-insulator transition

TL;DR

This paper investigates quantum-critical scaling of magneto-transport properties near a continuous metal-insulator transition in disordered systems using cluster-dynamical mean field theory, revealing unconventional critical behavior.

Contribution

It demonstrates the existence of quantum-critical scaling in Hall constant and transverse conductivity, supporting a strong localization perspective near the MIT.

Findings

Logarithmic gamma-function scaling over the MIT

Strong temperature dependence of R_H at the transition

Agreement with experimental NbN signatures

Abstract

In contrast to the seminal weak localization prediction of a non-critical Hall constant ($R_{H}$) at the Anderson metal-insulator transition (MIT), $R_{H}$ in quite a few real disordered systems exhibits both, a strong $T$-dependence and critical scaling near their MIT. Here, we investigate these issues in detail within a non-perturbative "strong localization" regime using cluster-dynamical mean field theory (CDMFT). We uncover $(i)$ clear and unconventional quantum-critical scaling of the $\gamma$-function, finding that $\gamma(g_{xy})\simeq$ log$(g_{xy})$ over a wide range spanning the continuous MIT, very similar to that seen for the longitudinal conductivity, $(ii)$ strongly $T$-dependent and clear quantum critical scaling in both transverse conductivity and $R_{H}$ at the MIT. We find that these surprising results are in comprehensive and very good accord with signatures of a novel kind of localization in disordered NbN near the MIT, providing substantial support for our "strong" localization view.