We report the condensation of microcavity exciton-polaritons at Γ points located on the boundary between the third and higher Brillouin zones in hexagonal lattices: triangular and honeycomb geometries. We collect experimental evidence that supports the finite momentum condensation: (1) the coherent Bragg peaks formed at nonzero Γ points; (2) the nonlinear intensity increase in the exciton-polariton emission at quantum degeneracy threshold; (3) the spectral linewidth behavior: narrowing near threshold and broadening above threshold; and (4) the equivalent 4fy3-3x2y-like orbital symmetry in real space. The f-orbital state at Γ points appears as a metastable momentum valley to trap exciton-polaritons, which is explained by single-particle band-structure calculations.
|Number of pages
|Physical Review. B, Condensed matter and materials physics
|Published - 12 Feb 2014