Absence of damping of low energy excitations in a quasi-2D dipolar Bose gas

TL;DR

This paper develops a theory for the damping of low energy collective excitations in a quasi-2D dipolar Bose gas, revealing a critical momentum threshold for decay processes and how it shifts with interaction strength, with experimental implications.

Contribution

It introduces a novel theoretical framework for understanding excitation damping in quasi-2D dipolar Bose gases, highlighting a critical momentum threshold for decay processes.

Findings

Decay processes only occur above a critical momentum k_{crit}

Increasing dipolar interaction shifts k_{crit} to larger momenta

Predictions are testable with current Bragg spectroscopy experiments

Abstract

We develop a theory of damping of low energy, collective excitations in a quasi-2D, homogenous, dipolar Bose gas at zero temperature, via processes whereby an excitation decays into two excitations with lower energy. We find that owing to the nature of the low energy spectrum of a quasi-2D dipolar gas, such processes cannot occur unless the momentum of the incoming quasi-particle exceeds a critical value k_{crit}. We find that as the dipolar interaction strength is increased, this critical value shifts to larger momenta. Our predictions can be directly verified in current experiments on dipolar Bose condensates using Bragg spectroscopy, and provide valuable insight into the quantum many-body physics of dipolar gases.