High sensitivity phonon spectroscopy of Bose-Einstein condensates using matter-wave interference

TL;DR

This paper introduces a highly sensitive matter-wave interference technique to study low-momentum phonon excitations in Bose-Einstein condensates, enabling access to the quantized quasiparticle regime with strong experimental-theoretical agreement.

Contribution

The work presents a novel interference-based spectroscopic method for probing phonons in BECs, validated by simulations, revealing new insights into quasiparticle regimes.

Findings

Strong matter-wave fringe patterns observed in time-of-flight images

Fringe contrast serves as a sensitive probe of in-trap phonons

Agreement between experimental data and Gross-Pitaevskii simulations

Abstract

We study low momentum excitations of a Bose-Einstein condensate using a novel matter-wave interference technique. In time-of-flight expansion images we observe strong matter-wave fringe patterns. The fringe contrast is a sensitive spectroscopic probe of in-trap phonons and is explained by use of a Bogoliubov excitation projection method applied to the rescaled order parameter of the expanding condensate. Gross-Pitaevskii simulations agree with the experimental data and confirm the validity of the theoretical interpretation. We show that the high sensitivity of this detection scheme gives access to the quantized quasiparticle regime.