Nonthermal switching of charge order: dynamical slowing down and optimal control

TL;DR

This paper explores how ultrafast laser pulses can induce nonthermal switching of charge order in materials, revealing multiple dynamical phases and demonstrating control over these states through pulse shaping.

Contribution

It provides a comprehensive mean-field analysis of nonthermal charge order switching, introduces a pseudospin model for understanding the dynamics, and applies optimal control to stabilize nonthermal phases.

Findings

Ultrafast switching and melting of charge order via nonthermal pathways.

Multiple dynamical phase transitions with increasing laser field strength.

Nonthermal states with slow relaxation can be stabilized by pulse shaping.

Abstract

We investigate the laser-induced dynamics of electronically driven charge-density-wave order. A comprehensive mean-field analysis of the attractive Hubbard model in the weak-coupling regime reveals ultrafast switching and ultrafast melting of the order via a nonthermal pathway. The resulting nonequilibrium phase diagram exhibits multiple dynamical phase transitions with increasing field strength. Using an intuitive pseudospin picture, we show that the laser can be regarded as a external (pseudo) magnetic field, and that the distinct dynamical regimes can be connected to the spin precession angle. We furthermore study the effects of electron-electron interactions beyond mean-field to show that the main features of the phase diagram are robust against scattering or thermalization processes. For example, the nonthermal state with switched order is characterized by a particularly slow relaxation. We also demonstrate how these nonthermal phases can be stabilized by tailoring the pulse shape with optimal control theory.