Alternate Oscillation between Scissors and Quadrupole Modes in Sodium Bose–Einstein Condensates

Abstract

Using an additional off-axis Helmholtz coil, we modulated the strength of a magnetic field at the center of a cloverleaf trap for sodium Bose–Einstein condensates so that it passed through zero for a few milliseconds. At a modulation time of 1 ms, a scissors mode and a high-lying quadrupole mode were generated independently, which had the same Landau damping rates of 39(10) 1/s. However, at 2 ms, alternate oscillation between the scissors mode and the high-lying quadrupole mode, whose frequency was twice that of the scissors mode, was observed with the frequency of the low-lying quadrupole mode.