How bad metals turn good: spectroscopic signatures of resilient quasiparticles

TL;DR

This paper studies the transport properties of strongly correlated metals, revealing that resilient quasiparticles persist above the Fermi liquid temperature and dominate transport until they vanish in the bad-metal regime, with implications for spectroscopic signatures.

Contribution

It demonstrates the existence of resilient quasiparticles above the Fermi liquid temperature in doped Mott insulators and links their disappearance to bad-metal behavior and spectroscopic signatures.

Findings

Resilient quasiparticles remain well-defined above T_FL

Particle-hole asymmetry affects thermopower

Optical spectroscopy signals quasiparticle disappearance

Abstract

We investigate transport in strongly correlated metals. Within dynamical mean-field theory, we calculate the resistivity, thermopower, optical conductivity and thermodynamic properties of a hole-doped Mott insulator. Two well-separated temperature scales are identified: T_FL below which Landau Fermi liquid behavior applies, and T_MIR above which the resistivity exceeds the Mott-Ioffe-Regel value and `bad-metal' behavior is found. We show that quasiparticle excitations remain well-defined above T_FL and dominate transport throughout the intermediate regime T_FL < T_MIR. The lifetime of these `resilient quasiparticles' is longer for electron-like excitations, and this pronounced particle-hole asymmetry has important consequences for the thermopower. The crossover into the bad-metal regime corresponds to the disappearance of these excitations, and has clear signatures in optical spectroscopy.