Sayak Ray — Page 2 | Searcharxiv

arXiv2015

Localization of weakly interacting Bose gas in quasiperiodic potential

We study the localization properties of weakly interacting Bose gas in a quasiperiodic potential commonly known as Aubry-André model. Effect of interaction on localization is investigated by computing the `superfluid fraction' and `inverse participation ratio'. For interacting Bosons the inverse participation ratio increases very slowly after the localization transition due to `multisite localization' of the wave function. We also study the localization in Aubry-André model using an alternative approach of classical dynamical map, where the localization is manifested by chaotic classical dynamics. For weakly interacting Bose gas, Bogoliubov quasiparticle spectrum and condensate fraction are calculated in order to study the loss of coherence with increasing disorder strength. Finally we discuss the effect of trapping potential on localization of matter wave.

cond-mat.quant-gas↗

arXiv2014

Effect of spin-orbit interaction on the critical temperature of an ideal Bose gas

We consider Bose-Einstein condensation of an ideal bose gas with an equal mixture of `Rashba' and `Dresselhaus' spin-orbit interactions and study its effect on the critical temperature. In uniform bose gas a `cusp' and a sharp drop in the critical temperature occurs due to the change in the density of states at a critical Raman coupling where the degeneracy of the ground states is lifted. Relative drop in the critical temperature depends on the diluteness of the gas as well as on the spin-orbit coupling strength. In the presence of a harmonic trap, the cusp in the critical temperature smoothened out and a minimum appears. Both the drop in the critical temperature and lifting of `quasi-degeneracy' of the ground states exhibit crossover phenomena which is controlled by the trap frequency. By considering a 'Dicke' like model we extend our calculation to bosons with large spin and observe a similar minimum in the critical temperature near the critical Raman frequency, which becomes deeper for larger spin. Finally in the limit of infinite spin, the critical temperature vanishes at the critical frequency, which is a manifestation of Dicke type quantum phase transition.

cond-mat.quant-gas↗