Symmetry Breaking and Enhanced Condensate Fraction of an Attractive Bose-Einstein Condensate.

Yvan Castin, Christopher P. Herzog

Masahito Ueda

Rina Kanamoto, Hiroki Saito, Masahito Ueda

An exact diagonalization study reveals that a matter-wave bright soliton and the Goldstone mode are simultaneously created in a quasi-one-dimensional attractive Bose-Einstein condensate by superpositions of quasidegenerate low-lying many-body states. Upon formation of the soliton the maximum eigenvalue of the single-particle density matrix increases dramatically, indicating that a fragmented condensate converts into a single condensate as a consequence of the breaking of translation symmetry.

J Hang

Masahito Ueda, Yuki Kawaguchi, Hiroki Saito +2 more

A gaseous Bose‐Einstein condensate (BEC) offers an ideal testing ground for studying symmetry breaking, because a trapped BEC system is in a mesoscopic regime, and situations exist under which symmetry breaking may or may not occur. Investigating this problem can explain why mean‐field theories have been so successful in elucidating gaseous BEC systems and when many‐body effects play a significant role. We substantiate these ideas in four distinct situations: namely, soliton formation in attractive BECs, vortex nucleation in rotating BECs, spontaneous magnetization in spinor BECs, and spin texture formation in dipolar BECs.

Roger A. Hegstrom