Scaling behaviour in the Bose gas

Elka Korutcheva, Dimo I. Uzunov

Rémi Desbuquois, Lauriane Chomaz, Tarik Yefsah +4 more

Carol K. Hall

W. Rohringer, D. Fischer, F. Steiner +3 more

We present experimental evidence for scale invariant behaviour of the excitation spectrum in phase-fluctuating quasi-1d Bose gases after a rapid change of the external trapping potential. Probing density correlations in free expansion, we find that the temperature of an initial thermal state scales with the spatial extension of the cloud as predicted by a model based on adiabatic rescaling of initial eigenmodes with conserved quasiparticle occupation numbers. Based on this result, we demonstrate that shortcuts to adiabaticity for the rapid expansion or compression of the gas do not induce additional heating.

Jeff Maki

Jian-hui Wang, Yong-li Ma

Within a canonical ensemble treatment, we study the finite-size scaling behaviour of the specific heat near the critical region for the weakly interacting Bose gases, and obtain the specific heat exponent α and correlation length exponent ν which agree well with experimental data and previous theoretical predictions. For the small and fixed interaction parameter an 1/3 with a being the scattering length and n the particle number density, we report for the first time that the dimensionless specific heats per particle c ( t , N ) for various system sizes ( L = ( N / n ) 1/3 in a square box potential) and reduced temperatures ( t = T / T c − 1) collapse onto a single form, and the borders of universality validity are obtained numerically. From scaling arguments, we study the interaction-induced shift of the transition temperature (Δ T c = T c − T 0 c ) and find that Δ T c / T 0 c = ban 1/3 with b = 0.42 ± 0.05, where T 0 c is the ideal-gas thermodynamic critical temperature. We also compare our findings with experimental and theoretical results for in cubic lattices, showing the very different behaviours for the two systems.