Professor Christopher Foot

Abstract:

We relate the frequency of the scissors mode to the moment of inertia of a trapped Bose gas at finite temperature in a semi-classical approximation. We apply these theoretical results to the data obtained in our previous study of the properties of the scissors mode of a trapped Bose-Einstein condensate of 87Rb atoms as a function of the temperature. The frequency shifts that we measured show quenching of the moment of inertia of the Bose gas at temperatures below the transition temperature - the system has a lower moment of inertia than that of a rigid body with the same mass distribution, because of superfluidity.

Abstract:

A simple model describing the nonlinear coupling of quasiparticle amplitudes of two modes is derived. The model, in particular, can be used to study squeezing effects that are directly related to the matrix element governing the coupling process. This paper demonstrates how to calculate this matrix element analytically and focuses on the quadrupole excitations.