Exact two-body quantum dynamics of an electron-hole pair in semiconductor coupled quantum wells: a time-dependent approach

TL;DR

This paper presents a time-dependent quantum simulation of an electron-hole pair in coupled quantum wells, capturing full two-particle dynamics and revealing transient phenomena that are not well-described by mean-field models.

Contribution

It introduces a comprehensive wave-packet propagation method for simulating two-dimensional electron-hole dynamics in coupled quantum wells, including Coulomb interactions and complex potentials.

Findings

Transient phenomena occur on picosecond timescales.

Exact simulations differ significantly from mean-field approaches.

Potential profiles influence transmission and reflection properties.

Abstract

We simulate the time-dependent coherent dynamics of a spatially indirect exciton (an electron-hole pair with the two particles confined in different layers) in a GaAs coupled quantum well system. We use a unitary wave-packet propagation method taking into account in full the four degrees of freedom of the two particles in a two-dimensional system, including both the long-range Coulomb attraction and arbitrary two-dimensional electrostatic potentials affecting the electron and/or the hole separately. The method has been implemented for massively parallel architectures to cope with the huge numerical problem, showing good scaling properties and allowing evolution for tens of picoseconds. We have investigated both transient time phenomena and asymptotic time transmission and reflection coefficients for potential profiles consisting of i) extended barriers and wells and ii) a single-slit geometry. We found clear signatures of the internal two-body dynamics, with transient phenomena in the picosecond time-scale which might be revealed by optical spectroscopy. Exact results have been compared with mean-field approaches which, neglecting dynamical correlations by construction, turn out to be inadequate to describe the electron-hole pair evolution in realistic experimental conditions.