Exciton many-body effects through infinite series of composite-exciton operators

TL;DR

This paper revisits a composite-exciton many-body theory, explicitly deriving all terms of infinite series of operators, providing a detailed framework for exciton interactions beyond previous approximations.

Contribution

It explicitly derives all terms of the infinite series of composite-exciton operators, enhancing the understanding of exciton many-body effects with a physically relevant operator basis.

Findings

All terms of the infinite series are explicitly obtained.

First terms match previous electron-hole pair results.

The approach connects to Pauli and interaction scatterings in exciton theory.

Abstract

We revisit the approach proposed by Mukamel and coworkers to describe interacting excitons through infinite series of composite-boson operators for both, the system Hamiltonian and the exciton commutator -- which, in this approach, is properly kept different from its elementary boson value. Instead of free electron-hole operators, as used by Mukamel's group, we here work with composite-exciton operators which are physically relevant operators for excited semiconductors. This allows us to get \emph{all} terms of these infinite series explicitly, the first terms of each series agreeing with the ones obtained by Mukamel's group when written with electron-hole pairs. All these terms nicely read in terms of Pauli and interaction scatterings of the composite-exciton many-body theory we have recently proposed. However, even if knowledge of these infinite series now allows to tackle $N$-body problems, not just 2-body problems like third order nonlinear susceptibility $\chi^{(3)}$, the necessary handling of these two infinite series makes this approach far more complicated than the one we have developed and which barely relies on just four commutators.