Component exchange theory of trions

TL;DR

This paper introduces a component exchange mechanism as the core process behind trion formation, modeled through a Bethe-Salpeter Equation that predicts binding energies consistent with three-body numerical methods.

Contribution

It develops a Bethe-Salpeter Equation framework for trions emphasizing component exchange, providing a parameter-efficient approach aligned with existing three-body calculations.

Findings

Component exchange explains trion formation.

Bethe-Salpeter Equation predicts binding energies accurately.

Distinguishable particles are essential for bound trion states.

Abstract

Treating the trion problem as an effective two-body system with exciton and electron components, we identify component exchange as the reason leading to trion formation. This mechanism can be visualized as a hole that toggles back and forth between two electrons. The coined term component exchange is meant to inform that the repeated change of the electron component of the exciton originates from the exchange interaction. We develop a Bethe-Salpeter Equation for trions, showing that a bound trion state emerges if the electron and electron of the exciton are distinguishable particles (e.g., having opposite spins or residing in different valleys of the Brillouin zone). Similar to numerical techniques that treat the trion as a three-body problem, the trion Bethe-Salpeter Equation yields similar binding energy without using parameters beyond effective masses and dielectric constants.