Absorption and Emission in quantum dots: Fermi surface effects of Anderson excitons

TL;DR

This paper investigates how many-body correlations from a Fermi sea influence the optical absorption and emission spectra in quantum dots, revealing power-law divergences and threshold shifts linked to Kondo physics and exciton binding energy.

Contribution

It extends the Anderson model to include valence levels and uses numerical renormalization group to analyze Fermi sea effects on quantum dot spectra, highlighting novel many-body phenomena.

Findings

Spectra exhibit power law divergence near threshold.

Threshold energy shifts monotonically with exciton binding energy.

Fermi sea hybridization affects optical properties of quantum dots.

Abstract

Recent experiments measuring the emission of exciton recombination in a self-organized single quantum dot (QD) have revealed that novel effects occur when the wetting layer surrounding the QD becomes filled with electrons, because the resulting Fermi sea can hybridize with the local electron levels on the dot. Motivated by these experiments, we study an extended Anderson model, which describes a local conduction band level coupled to a Fermi sea, but also includes a local valence band level. We are interested, in particular, on how many-body correlations resulting from the presence of the Fermi sea affect the absorption and emission spectra. Using Wilson's numerical renormalization group method, we calculate the zero-temperature absorption (emission) spectrum of a QD which starts from (ends up in) a strongly correlated Kondo ground state. We predict two features: Firstly, we find that the spectrum shows a power law divergence close to the threshold, with an exponent that can be understood by analogy to the well-known X-ray edge absorption problem. Secondly, the threshold energy $\omega_0$ - below which no photon is absorbed (above which no photon is emitted) - shows a marked, monotonic shift as a function of the exciton binding energy $U_{\rm exc}$