Historically, measurements of electronic transport have often given the first indication of new physical concepts arising from interaction effects in condensed matter systems. Famous examples range from metalinsulator transitions and superconductivity to the Kondo and fractional quantum Hall effects. When measurements of the electric conductivity are supplemented by thermal transport experiments, even more profound insights into the manybody effects may be gained. For example, a wellknown metric of the strength of interactions in a metal is given by the ratio of thermal and electric conductivities. When both electric and thermal currents are carried by noninteracting electrons, the WiedemannFranz law states that this ratio is given by a universal coefficient times temperature. Most conventional metals satisfy this law to a high accuracy despite the presence of electronelectron interactions; its violations indicate deviations from Landau’s Fermiliquid theory. Important examples of such WiedemannFranz law violations occur in diffusive, interacting electron fluids at low temperatures as well as in highTc cuprates above the superconducting transition or in heavyfermion systems.
Deviations from WiedemannFranz law behavior arise because thermal conductivity is affected more strongly by interactions than electric conductivity. Our group seeks to advance the understanding of how material properties like disorder, interactions, or nearlycritical fluctuations affect the electric and thermal transport coefficients. We apply these insights to search for new thermoelectric devices with improved efficiency.
Relevant Publications

D. Klein, K. Michaeli, Landauer formula for interacting systems: a consistent nonperturbative approximation, arXiv:2203.16572
 W.R. Lee, K. Michaeli, and G. Schwiete, Lorenz ratio of an impure compensated metal in the degenerate Fermi liquid regime, Phys. Rev. B 103, 115140 (2021).

W.R. Lee, A. M. Finkel'stein, K. Michaeli, and G. Schwiete, Role of electronelectron collisions for charge and heat transport at intermediate temperatures, Phys. Rev. Research 2, 013148 (2020).

K. Michaeli, and A. M. Finkel'stein, Quantum kinetic approach to the calculation of the Nernst effect, Phys. Rev. B 80, 214516 (2009).

K. Michaeli, and A. M. Finkel'stein, Quantum kinetic approach for studying thermal transport in the presence of electronelectron interactions and disorder", Phys. Rev. B 80, 115111 (2009).