Superfluid fraction of an ultracold interacting boson atoms trapped in a combined harmonic-deep optical potential

In this letter the superfluid fraction of rotating Bose-Einstein condensates trapped in a combined harmonic-deep optical potential at finite temperature is calculated. Two scenarios are considered, including rotating condensate boson atoms in a combined harmonic-1D axial optical potential and rotation in a combined harmonic-2D radial deep optical potential. Based on the Hellman-Feynman theorem, the thermal average angular momentum and square radius (in situ size) are derived in terms of the thermodynamic potential. The obtained results shows that the superfluid fraction has a monotonically decreasing nature due to the increase of the normalized temperature T. The superfluid fraction shows significant dependence on the interatomic interaction and optical potential depth. The out come results furnish useful qualitative theoretical results for the future BEC experiments in such traps. •Superfluidity nature of ultracold boson atoms in a deep optical lattice is investigated.•The temperature dependence of the angular momentum is calculated.•The effects of the interatomic interaction and optical potential depth are investigated.