Quantum-critical relativistic magnetotransport in graphene

TL;DR

This paper investigates the thermal and electrical transport properties of interacting Dirac fermions in graphene under magnetic fields, revealing deviations from Fermi liquid behavior and providing a comprehensive analysis across different regimes.

Contribution

It offers a detailed Boltzmann approach to quantum-critical magnetotransport in graphene, extending beyond hydrodynamics to include disorder, high fields, and frequency dependence.

Findings

Discovery of a collective cyclotron resonance with collision broadening.

Significant enhancement of Mott and Wiedemann-Franz ratios in the quantum-critical regime.

Quantitative description of the universal conductivity sigma_Q across various regimes.

Abstract

We study the thermal and electric transport of a fluid of interacting Dirac fermions using a Boltzmann approach. We include Coulomb interactions, a dilute density of charged impurities and the presence of a magnetic field to describe both the static and the low frequency response as a function of temperature T and chemical potential mu. In the quantum-critical regime mu << T we find pronounced deviations from Fermi liquid behavior, such as a collective cyclotron resonance with an intrinsic, collision-broadened width, and significant enhancements of the Mott and Wiedemann-Franz ratio. Some of these results have been anticipated by a relativistic hydrodynamic theory, whose precise range of validity and failure at large fields and frequencies we determine. The Boltzmann approach allows us to go beyond the hydrodynamic regime, and to quantitatively describe the deviations from magnetohydrodynamics, the crossover to disorder dominated Fermi liquid behavior at large doping and low temperatures, as well as the crossover to the ballistic regime at high fields. Finally, we obtain the full frequency and doping dependence of the single universal conductivity sigma_Q which parametrizes the hydrodynamic response.