Excitation-induced defects in photonic band gaps in a lattice Bose-Einstein condensate

Abstract

Summary form only given. Recent research is rapidly moving toward all-optical confinement of Bose-Einstein condensate (BEC) in optical traps. The optical trap provides an effective tool to manipulate the dynamics of BEC for practical purposes. In particular it opens the possibilities to study BEC in an optical lattice. In this work, we focus on studying the properties of propagation of a weak probe light through a BEC confined in an optical lattice. The key point in the topic is that the ground state of the lattice BEC acts as a periodic dielectric medium for the probe light propagating through it. We show that photonic, or rather polaritonic band gaps are created for probe light due to the spatial periodicity of the ground state of the lattice BEC. However being different from the ordinary periodic dielectric, the lattice BEC can experience elementary excitations which lead to a perturbative distortion of the periodicity of the lattice BEC. Such non-periodic perturbations are similar to lattice defects in solid state physics. Here they will produce defect states inside the photonic band gaps. By analyzing the elementary excitations of the lattice BEC, we study the frequency spectrum of photonic band gaps and defect states induced by such excitations in the lattice BEC. These photonic defect states may technically have the potential to be employed to acquire knowledge about the quantum degeneracy in an optical lattice.