Linear response theory for electron-hole pair kinetics: exciton formation

TL;DR

This paper develops a linear response theory to analyze electron-hole pair dynamics and exciton formation from first principles, revealing transient excitons and their evolution with electron density.

Contribution

A novel linear response framework for electron-hole pairs that defines exciton density and examines its time evolution from first principles.

Findings

Existence of transient excitons demonstrated

Crossover from transient to stable excitons observed

Exciton formation mechanism elucidated

Abstract

A linear response theory for electron-hole pair density is developed, which constitutes a new theoretical method, and a definition of exciton density in a first-principles context is derived by considering both the electron-hole attractive interaction and the screening effect. This allows the exciton time evolution to be examined. This formulation is applied to a jellium model in order to prove the existence of a transient exciton, and to observe crossover from a transient to a stable exciton in response to decreased electron density. The exciton formation mechanism is also revealed.