Many-body correlations brought to light in absorption spectra of diluted magnetic semiconductors

TL;DR

This paper demonstrates that exciton-magnetic impurity interactions in diluted magnetic semiconductors cause notable spectral features and shifts, revealing strong many-body correlations that can be quantified directly from absorption spectra.

Contribution

It shows that exciton-impurity correlations significantly alter absorption spectra, providing a method to extract correlation energies and generalizing to other strongly correlated systems.

Findings

Additional spectral feature near exciton resonance

Shift of exciton line by a few meV

Correlation energy can be extracted from spectra

Abstract

Diluted magnetic semiconductors are materials well known to exhibit strong correlations which typically manifest in carrier-mediated magnetic ordering. In this Rapid Communication, we show that the interaction between excitons and magnetic impurities in these materials is even strong enough to cause a significant deviation from the bare exciton picture in linear absorption spectra of quantum well nanostructures. It is found that exciton-impurity correlations induce a characteristic fingerprint in the form of an additional feature close to the exciton resonance in combination with a shift of the main exciton line of up to a few meV. We trace back these features to the form of the self-energy and demonstrate that reliable values of the average correlation energy per exciton can be extracted directly from the spectra. Since the only requirement for our findings is sufficiently strong correlations, the results can be generalized to other strongly correlated systems.