Z_(2) SYMMETRY BREAKING IN MULTI-BAND BOSONIC ATOMS CONFINED BY A TWO-DIMENSIONAL HARMONIC POTENTIAL

摘要

When a two-dimensional harmonic potential is applied to bosonic cold atoms, the atoms become a cigar shape and the radial energy level is discretized. If the strength of the potential or the total number of atoms is tuned, the atoms can occupy not only the lowest radial band but also higher bands. This paper shows that when both the lowest band and the second lowest doubly-degenerate bands are filled, the repulsive interaction among atoms induces a ground state circulating along the trap axis, in which the Z_(2) reflection symmetry is spontaneously broken.