Eur. Phys. J. D (2014) 68: 232
https://doi.org/10.1140/epjd/e2014-50340-y

Regular Article

Signatures of Bose-Einstein condensation in an optical lattice

¹ Department of Physics, Renmin University of China, Beijing 100872, P.R. China
² Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, Anhui 230026, P.R. China
³ Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, P.R. China
⁴ Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, P.R. China

^a e-mail: wyiz@ustc.edu.cn
^b e-mail: wzhangl@ruc.edu.cn

Received: 30 April 2014
Received in final form: 3 June 2014
Published online: 14 August 2014

Abstract

We discuss typical experimental signatures for the Bose-Einstein condensation (BEC) of an ultracold Bose gas in an inhomogeneous optical lattice at finite temperature. Applying the Hartree-Fock-Bogoliubov-Popov formalism, we calculate quantities such as the momentum-space density distribution, visibility and peak width as the system is tuned through the superfluid to normal phase transition. Different from previous studies, we consider systems with fixed total particle number, which is of direct experimental relevance. We show that the onset of BEC is accompanied by sharp features in all these signatures, which can be probed via typical time-of-flight imaging techniques. In particular, we find a two-platform structure in the peak width across the phase transition. We show that the onset of condensation is related to the emergence of the higher platform, which can be used as an effective experimental signature.