Femtosecond Coherent Dynamics of the Fermi Edge Singularity and Exciton Hybrid

TL;DR

This paper theoretically investigates the nonlinear optical response of doped semiconductors, revealing a dynamic interplay between Fermi-edge singularity and exciton resonances driven by many-body correlations.

Contribution

It introduces a novel theoretical framework combining coupled cluster and Schrieffer-Wolff methods to analyze the coherent nonlinear optical dynamics in doped semiconductors.

Findings

Double-peak absorption spectrum from Fermi-edge singularity and exciton interference

Time-dependent exchange of oscillator strength in pump/probe spectra

Identification of many-body correlations as key to the dynamical response

Abstract

We study theoretically the coherent nonlinear optical response of doped semiconductors with partially occupied subbands. When the Fermi energy of an occupied subband approaches the exciton level of an upper subband, the absorption spectrum acquires a characteristic double-peak shape originating from the interference between the Fermi-edge singularity and the exciton resonance. We demonstrate that, for the off-resonant pump excitation, the pump/probe spectrum undergoes a dramatic transformation in the coherent regime, with a strong time-dependent exchange of oscillator strength between Fermi edge singularity and exciton peaks. We show that this effect originates from the many-body electron-hole correlations which determine the dynamical response of the Fermi see. To calculate the nonlinear absorption spectrum, we use the coupled cluster method combined with time-dependent Schrieffer-Wolff transformation. Possible experimental applications are discussed.