Propagating Coherent Acoustic Phonon Wavepackets in InMnAs/GaSb

TL;DR

This paper demonstrates that oscillations in differential reflectivity of an InMnAs/GaSb heterostructure are caused by coherent acoustic phonons, with experimental and theoretical analysis confirming their origin and properties.

Contribution

The study reveals that observed oscillations are due to coherent acoustic phonons, challenging previous assumptions linking them to ferromagnetism, and provides a predictive theoretical model.

Findings

Oscillations are caused by coherent acoustic phonons.

Theoretical predictions match experimental measurements.

Oscillation period and decay depend on probe wavelength.

Abstract

We observe pronounced oscillations in the differential reflectivity of a ferromagnetic InMnAs/GaSb heterostructure using two-color pump-probe spectroscopy. Although originally thought to be associated with the ferromagnetism, our studies show that the oscillations instead result from changes in the position and frequency-dependent dielectric function due to the generation of coherent acoustic phonons in the ferromagnetic InMnAs layer and their subsequent propagation into the GaSb. Our theory accurately predicts the experimentally measured oscillation period and decay time as a function of probe wavelength.