Damping of bulk excitations over an elongated BEC - the role of radial modes

TL;DR

This study investigates Beliaev damping in elongated Bose-Einstein condensates, revealing how damping rates depend on excitation energy and momentum, with a model aligning well with experimental data.

Contribution

It provides a detailed measurement and modeling of Beliaev damping in cigar-shaped BECs, highlighting the role of radial modes and quantum interference effects.

Findings

Damping depends on initial excitation energy and momentum.

The model accurately predicts damping rates for different radial modes.

Quantum interference influences damping pathways significantly.

Abstract

We report the measurement of Beliaev damping of bulk excitations in cigar shaped Bose Einstein condensates of atomic vapor. By using post selection, excitation line shapes of the total population are compared with those of the undamped excitations. We find that the damping depends on the initial excitation energy of the decaying quasi particle, as well as on the excitation momentum. We model the condensate as an infinite cylinder and calculate the damping rates of the different radial modes. The derived damping rates are in good agreement with the experimentally measured ones. The damping rates strongly depend on the destructive interference between pathways for damping, due to the quantum many-body nature of both excitation and damping products.