Abstract

Bose-Einstein condensates (BECs) are a macroscopic state of quantum matter at temperatures nine orders of magnitude colder than outer space. BECs can be trapped in crystals of light: when the crystal takes the form of a honeycomb optical lattice, Dirac physics arises at the Brillouin zone edges, just like in graphene. The weakly interacting quantum gas comprising the BEC generates an effective nonlinearity, giving rise to the nonlinear Dirac equation (NLDE) [1], as we will show. This equation, together with the relativistic linear stability equations (RLSE) [2], comprise a relativistic generalization of the famous nonlinear Schrodinger equation and Boguliubov-de Gennes equations familiar from, for example, propagation of light in Kerr nonlinear media. We present a zoo of exotic vortex [3], skyrmion, and soliton [4,5] solutions to the NLDE+RLSE system, and explain the practical realization of these concepts in present experiments on BECs in the optical equivalent of 2D graphene and 1D armchair and zigzag graphene nanoribbons.

© 2014 Optical Society of America