Ultrafast Mott transition driven by nonlinear electron-phonon interaction

TL;DR

This paper demonstrates that ultrashort pulse excitation of nonlinear phonons can induce a Mott insulator-to-metal transition, emphasizing the importance of phononic fluctuations and dynamic effects in quantum materials.

Contribution

It introduces an exact diagonalization approach within nonequilibrium dynamical mean-field theory to study nonlinear electron-phonon interactions and their role in phase transitions.

Findings

Ultrashort phonon excitation can trigger a Mott transition.

Phononic fluctuations significantly influence quasiparticle formation.

Mean-field approaches underestimate the transition onset.

Abstract

Nonlinear phononics holds the promise for controlling properties of quantum materials on the ultrashort timescale. Using nonequilibrium dynamical mean-field theory, we solve a model for the description of organic solids, where correlated electrons couple nonlinearly to a quantum phonon mode. Unlike previous works, we exactly diagonalize the local phonon mode within the noncrossing approximation to include the full phononic fluctuations. By exciting the local phonon in a broad range of frequencies near resonance with an ultrashort pulse, we show it is possible to induce a Mott insulator-to-metal phase transition. Conventional semiclassical and mean-field calculations, where the electron-phonon interaction decouples, underestimate the onset of the quasiparticle peak. This fact, together with the nonthermal character of the photoinduced metal, suggests a leading role of the phononic fluctuations and of the dynamic nature of the state in the vibrationally induced quasiparticle coherence.