Dynamical d-wave condensation of exciton-polaritons in a two-dimensional square-lattice potential

Abstract

Macroscopic order appears as the collective behaviour of many interacting particles. Prime examples are superfluidity in helium, atomic Bose-Einstein condensation, s-wave and d-wave superconductivity and metal-insulator transitions. Such physical properties are tightly linked to spin and charge degrees of freedom and are greatly enriched by orbital structures. Moreover, high-orbital states of bosons exhibit exotic orders distinct from the orders with real-valued bosonic ground states. Recently, a wide range of related phenomena have been studied using atom condensates in optical lattices, but the experimental observation of high-orbital orders has been limited to momentum space. Here we establish microcavity exciton-polariton condensates as a promising alternative for exploring high-orbital orders. We observe the formation of d-orbital condensates on a square lattice and characterize their coherence properties in terms of population distributions both in real and momentum space. © 2011 Macmillan Publishers Limited. All rights reserved.