Dissociation of a Hubbard--Holstein bipolaron driven away from equilibrium by a constant electric field

TL;DR

This study uses a variational numerical approach to analyze how a Holstein-Hubbard bipolaron responds to a constant electric field, revealing its dissociation and current behavior under different regimes.

Contribution

It introduces a full quantum time-evolution method to study bipolaron dynamics under electric fields, highlighting the dissociation process and steady-state current formation.

Findings

Bipolaron remains bound with zero current at low fields.

Finite steady-state current causes bipolaron dissociation at higher fields.

System exhibits Bloch oscillations in the adiabatic regime.

Abstract

Using a variational numerical method we compute the time-evolution of the Holstein-Hubbard bipolaron from its ground state when at t=0 the constant electric field is switched on. The system is evolved taking into account full quantum effects until it reaches a quasi-stationary state. In the zero-field limit the current shows Bloch oscillations characteristic for the adiabatic regime where the electric field causes the bipolaron to evolve along the quasiparticle band. Bipolaron remains bound and the net current remains zero in this regime. At larger electric fields the system enters the dissipative regime with a finite steady-state current. Concomitantly, the bipolaron dissociates into two separate polarons. By examining different parameter regimes we show that the appearance of a finite steady-state current is inevitably followed by the dissociation of the bipolaron.