Semiclassical analysis of frustrated Bose gases in optical kagome lattices

Frustration, which causes extensive degeneracy near the ground state of a many-body system, has received considerable interest because it is an essential component for understanding the various emergent phenomena in many-body systems [1]. Specifically, in the case of non-interacting particles on a kagome lattice, a flat band appears as a clear feature of the frustration.
In this talk, we consider spinless bosons with sign-inverted hopping on the kagome lattice within the regime of weak quantum fluctuations. Since the single particle energies are degenerate in the flat band, the interaction plays a dominant role in determining various properties of the kagome-lattice system. In addition, the previous work [2] suggested that quantum fluctuations resolve the degeneracy and there exist three different phases depending on the temperature. Here we focus on a weak-interaction and high-density regime where quantum fluctuations are weak. We investigate whether these quantum states can be realized and identified in ultracold-gas experiments by calculating non-equilibrium dynamics within the truncated Wigner approximation.

[1] H. Diep, Frustrated Spin Systems (World Scientific, Singapore, 2004).
[2] Y.-Z. You, Z. Chen, X.-Q. Sun, and H. Zhai, Physical Review Letters 109, 265302 (2012).