Dynamics of Quantized Vortices in Bose-Einstein Condensates Trapped in Precessing Potential

We study numerically and analytically dynamics of Bose-Einstein condensates trapped in precessing potential. The precessing potential has two frequencies because the trapping potential rotates around one axis with one frequency, and this axis rotates around the other axis with the other frequency. In this paper, we treat a situation in which the second frequency is much smaller than the first. The vortex lattice formed by the first rotation rotates around the second axis, following the rotating axis. We find numerically an interesting steady state in which the vortex lattice lags by a finite angle behind the rotating axis. We discuss analytically the origin of this steady state.