Statistical fluctuations and quasi phase transition of mesoscopic Bose–Einstein condensation in anharmonic trap

The possibility of quasi phase transition of interacting Bose gas in mesoscopic regime and in the anharmonic trap is studied by a correlated two-body basis function approach. Our methodology accurately describes all measures of statistical fluctuations in anharmonic trap with different anharmonicity. The results addressed here go beyond the mean-field theory, correctly describe finite-sized effect and one unique formalism is valid for entire temperature region. Our main discovery : the lambda-structure in all fluctuation measures near the transition temperature remains same qualitatively in all traps. We also define three characteristic temperatures calculated from the point of inflexion of the lambda-structure of standard deviation, third and fourth central moment. All the three characteristic temperatures smoothly increase with increase in anharmonicity which jointly confirm that the achievement of condensation is more favourable in anharmonic trap. The possibility of true phase transition is ruled out for all traps for the mesoscopic Bose–Einstein condensate. However the additional calculation of transition exponent for the specific heat capacity nicely exhibits that quasi phase transition is more prominent in harmonic trap in comparison with anharmonic traps.