Exciting Collective Oscillations in a Trapped 1D Gas

TL;DR

This paper demonstrates the experimental realization and characterization of a one-dimensional Bose gas, analyzing its collective oscillations to explore quantum and thermal regimes, including the transition to strong interactions.

Contribution

It provides the first detailed measurement of collective excitations in a trapped 1D Bose gas, confirming theoretical predictions and exploring the transition between quantum and thermal regimes.

Findings

Measured the ratio of collective mode frequencies in quantum and thermal regimes.

Confirmed theoretical predictions for frequency ratios in a 1D Bose gas.

Explored the transition to the strongly interacting regime at low particle numbers.

Abstract

We report on the realization of a trapped one dimensional Bose gas and its characterization by means of measuring its lowest lying collective excitations. The quantum degenerate Bose gas is prepared in a 2D optical lattice and we find the ratio of the frequencies of the lowest compressional (breathing) mode and the dipole mode to be $(\omega_B/\omega_D)^2\simeq3.1$, in accordance with the Lieb-Liniger and mean-field theory. For a thermal gas we measure $(\omega_B/\omega_D)^2\simeq4$. By heating the quantum degenerate gas we have studied the transition between the two regimes. For the lowest number of particles attainable in the experiment the kinetic energy of the system is similar to the interaction energy and we enter the strongly interacting regime.