Phonon-induced disorder in dynamics of optically pumped metals from nonlinear electron-phonon coupling

John Sous,David R Reichman,Benedikt Kloss,Andrew J Millis,Dante M Kennes

doi:10.1038/s41467-021-26030-3

Abstract

The non-equilibrium dynamics of matter excited by light may produce electronic phases, such as laser-induced high-transition-temperature superconductivity, that do not exist in equilibrium. Here we simulate the dynamics of a metal driven at initial time by a spatially uniform pump that excites dipole-active vibrational modes which couple nonlinearly to electrons. We provide evidence for rapid loss of spatial coherence, leading to emergent effective disorder in the dynamics, which arises in a system unitarily evolving under a translation-invariant Hamiltonian, and dominates the electronic behavior as the system evolves towards a correlated electron-phonon long-time state, possibly explaining why transient superconductivity is not observed. Our framework provides a basis within which to understand correlation dynamics in current pump-probe experiments of vibrationally coupled electrons, highlight the importance of the evolution of phase coherence, and demonstrate that pumped electron-phonon systems provide a means of realizing dynamically induced disorder in translation-invariant systems.

Highlights

The non-equilibrium dynamics of matter excited by light may produce electronic phases, such as laser-induced high-transition-temperature superconductivity, that do not exist in equilibrium
Prior studies of nonlinear electron–phonon dynamics have relied on approximate low-energy treatments
We explicitly describe the flow towards a correlated electron–phonon steady state at long times, the indication of which already manifests on short timescales

Summary

Introduction

The non-equilibrium dynamics of matter excited by light may produce electronic phases, such as laser-induced high-transition-temperature superconductivity, that do not exist in equilibrium. The presence of quasi-conserved phonon constants of motion implies that electronic observables self-average over the different disordered phonon configurations of the initial state and possess no off-diagonal coherence between different phonon sectors This provides a realization of disorder-free localization[24,25,26], recently discussed in the context of lattice gauge theories[27,28,29,30,31]. The early-time dynamics that follow the pump already indicate rapid growth of local, negative correlations between the electron density n^ and the oscillator quadratic displacement X^2 at a given site and between the linear displacement X^ at adjacent sites, which signals a tendency towards charge flow between neighboring sites, resulting in enhanced double occupancy. We find an overall increase in the magnitude of the expectation value of the electron–phonon interaction term, implying evolution towards a strongly correlated long-time electron–phonon state

Methods

Results

Conclusion