Collective excitations of unconventional two-species Bose-Einstein condensation in the p-orbital bands of two-dimensional hybrid optical lattices

Unconventional Bose-Einstein condensation (BEC) arising in the metastable high orbital states of a quantum many-body system has been a topical subject in the recent years [1-4]. Based on a modified imaginary-time propagation method in momentum space, we had previously investigated the unconventional BEC in the two-species mixture with p-wave symmetry in the second band of a bipartite optical lattice [1-3,5], and shown that such a system undergoes a phase transition from a complex staggered-orbital state to a real checkerboard-like spin-density state when the strength of inter-species interaction overtakes its intra-species counterpart. In this presentation, we follow up to study the stability of such unconventional BEC state in the bipartite square lattice and a hybrid square lattice [6] by looking into the properties of its collective excitations which are obtained by numerically solving the Bogoliubov-de-Genne equation.

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