Nonequilibrium "melting" of a charge density wave insulator via an ultrafast laser pulse

TL;DR

This paper uses an exact model to show how ultrafast laser pulses can temporarily close the energy gap in charge density wave insulators like TaS2 and TbTe3, revealing universal nonequilibrium dynamics.

Contribution

It provides a simple, exact theoretical framework to understand the ultrafast melting and reformation of charge density wave gaps in nonequilibrium conditions.

Findings

Gap disappears during pulse but charge modulation remains

Gap reforms after pulse passage

Qualitative agreement with experimental short-time dynamics

Abstract

We employ an exact solution of the simplest model for pump-probe time-resolved photoemission spectroscopy in charge-density-wave systems to show how, in nonequilibrium the gap in the density of states disappears while the charge density remains modulated, and then the gap reforms after the pulse has passed. This nonequilibrium scenario qualitatively describes the common short-time experimental features in TaS2 and TbTe3 indicating a quasiuniversality for nonequilibrium "melting" with qualitative features that can be easily understood within a simple picture.