Emergence of an unconventional Bose-Einstein condensate in higher orbitals of a hexagonal lattice

Atoms in higher lattice orbitals provide new possibilities for realizing exotic quantum many-body states without an analogue in traditional condensed matter systems. In our experiment, we drive a bosonic ensemble of cold atoms in a bipartite hexagonal lattice into a non-equilibrium state by a rapid quench of the sublattice energy offset. The subsequent dynamics reveal the emergence of coherence and long-range order in higher orbital states and the evolution to an unconventional Bose-Einstein condensate in the two degenerate minima Κ and Κ′ of the second Bloch band. Numerical simulations indicate that atoms remaining in the first Bloch band support the condensation by acting as an efficient heat sink. Final temperature and interactions critically influence the nature of the resulting superfluid, which can be either fragmented or in a coherent superposition at Κ and Κ′.