Quantum nonlinear phononics route towards nonequilibrium materials engineering: Melting dynamics of a ferrielectric charge density wave

TL;DR

This paper explores how ultrashort laser pulses can induce and control phase transitions in quantum materials by leveraging nonlinear electron-phonon interactions, specifically focusing on ferrielectric charge density waves and their melting dynamics.

Contribution

It provides a microscopic analysis of quantum nonlinear phononics and demonstrates how laser-driven dynamics can manipulate ferrielectric and charge density wave states.

Findings

Observation of coherent phonon oscillations softening near phase transition

Identification of laser-induced melting dynamics of FE-CDW

First microscopic study of quantum nonlinear phononics in nonequilibrium

Abstract

Negative nonlinear electron-phonon coupling involving an infrared-active phonon mode can lead to an instability towards the formation of a polar lattice distortion with ferrielectric (FE) moments accompanied by an electronic charge-density wave (CDW). Analyzing a small model system in and out of thermal equilibrium, we investigate the FE-CDW and its melting dynamics following an ultrashort laser pulse that drives the ionic dipoles. We observe nonequilibrium coherent phonon amplitude mode oscillations that soften towards the transition to the normal phase. Our case study serves as a first step towards a microscopic understanding of quantum nonlinear phononics as a basis for nonequilibrium control in quantum materials.