Free induction signal from biexcitons and bound excitons

TL;DR

This paper develops a theoretical model for the free induction signals from biexcitons and bound excitons, revealing unique time-dependent behaviors including oscillations and rapid radiative decay, with potential applications in ultrafast optics.

Contribution

It introduces a new formalism describing the free induction signals from biexcitons and bound excitons, accounting for their simultaneous existence and resulting in novel time dependence features.

Findings

Signal increases over time and oscillates with growing amplitude.

Radiative decay can be extremely fast, producing picosecond pulses.

The formalism applies to various biexciton transient phenomena.

Abstract

A theory of the free induction signal from biexcitons and bound excitons is presented. The simultaneous existence of the exciton continuum and a bound state is shown to result in a new type of time dependence of the free induction. The optically detected signal increases in time and oscillates with increasing amplitude until damped by radiative or dephasing processes. Radiative decay is anomalously fast and can result in strong picosecond pulses. The expanding area of a coherent exciton polarization (inflating antenna), produced by the exciting pulse, is the underlying physical mechanism. The developed formalism can be applied to different biexciton transients.