Rise and Fall of Landau's Quasiparticles While Approaching the Mott Transition

TL;DR

This paper investigates how quasiparticles in correlated metals behave near the Mott transition, showing their persistence and eventual dissolution, which explains the emergence of bad metallic behavior.

Contribution

It provides experimental evidence and a theoretical model demonstrating the persistence and collapse of Landau quasiparticles approaching the Mott insulator transition.

Findings

Persistent Fermi-liquid behavior near the transition

Quadratic temperature and frequency dependence of scattering rate

Displaced Drude peak indicating dynamical localization

Abstract

Landau suggested that the low-temperature properties of metals can be understood in terms of long-lived quasiparticles with all complex interactions included in Fermi-liquid parameters, such as the effective mass $m^{\star}$. Despite its wide applicability, electronic transport in bad or strange metals and unconventional superconductors is controversially discussed towards a possible collapse of the quasiparticle concept. Here we explore the electrodynamic response of correlated metals at half filling for varying correlation strength upon approaching a Mott insulator. We reveal persistent Fermi-liquid behavior with pronounced quadratic dependences of the optical scattering rate on temperature and frequency, along with a puzzling elastic contribution to relaxation. The strong increase of the resistivity beyond the Ioffe-Regel-Mott limit is accompanied by a `displaced Drude peak' in the optical conductivity. Our results, supported by a theoretical model for the optical response, demonstrate the emergence of a bad metal from resilient quasiparticles that are subject to dynamical localization and dissolve near the Mott transition.