Time-domain pumping a quantum-critical charge-density-wave-ordered material

TL;DR

This study uses time-resolved photoemission spectroscopy to investigate the ultrafast dynamics of a quantum-critical charge-density-wave system, revealing unique relaxation channels and spectral changes during pump-probe experiments.

Contribution

It provides an exact theoretical analysis of nonequilibrium electron dynamics in a charge-density-wave material at quantum criticality using dynamical mean-field theory.

Findings

Quantum critical charge density wave exhibits ultra-efficient relaxation channels.

Spectral features such as band narrowing and gap reduction occur during pumping.

Spectral properties rapidly recover after the pump pulse ends.

Abstract

We determine the exact time-resolved photoemission spectroscopy for a nesting driven charge-density-wave (described by the spinless Falicov-Kimball model within dynamical mean-field theory). The pump-probe experiment involves two light pulses: the first is an ultrashort intense pump pulse that excites the system into nonequilibrium, and the second is a lower amplitude higher frequency probe pulse that photoexcites electrons. We examine three different cases: the strongly correlated metal, the quantum-critical charge density wave and the critical Mott insulator. Our results show that the quantum critical charge density wave has an ultra efficient relaxation channel that allows electrons to be de-excited during the pump pulse, resulting in little net excitation. In contrast, the metal and the Mott insulator show excitations that are closer to what one expects from these systems. In addition, the pump field produces spectral band narrowing, peak sharpening, and a spectral gap reduction, all of which rapidly return to their field free values after the pump is over.