Speaker
Description
We investigate the thermodynamics of the two-dimensional Bose gas within the framework of the non-perturbative functional renormalization group (NP-FRG) and quantum phase transitions. The existence of a quantum critical point in the vacuum-superfluid transition implies that thermodynamic functions can be expressed as universal scaling functions [1]. Furthermore, using the flow equations of the NP-FRG derived from the second-order derivative expansion, we demonstrate how to determine these universal quantities and characterize the low-temperature phase, which exhibits algebraic order and Berezinskii-Kosterlitz-Thouless (BKT) physics [2]. From the NP-FRG flow equations, we show how to calculate the gas's equation of state and its superfluid density, thereby fully characterizing its thermodynamics : from Tan's contact to sound velocities. Our calculations exhibit remarkable agreement with experimental observations. To illustrate this, we compare our results to recent cold atoms experiments [3,4]. We also demonstrate that the method is robust by comparing different approximation.
[1] A. Rançon and N. Dupuis, Phys. Rev. A 85, 063607 (2012).
[2] P. Jakubczyk, N. Dupuis and B. Delamotte, Phys. Rev. E 90, 062105 (2014).
[3] T. Yefsah, R. Desbuquois, L. Chomaz, K. J. Gunter and J. Dalibard, Phys. Rev. Lett. 107, 130401 (2011).
[4] P. Christodoulou, M. Gałka, N. Dogra, R. Lopes, J. Schmitt and Z. Hadzibabic Nature 594, 191–194 (2021).
| Affiliation | PhLam Laboratory, University of Lille |
|---|---|
| Career status | PhD student |