Superfluidity at Finite Temperatures and Hydrodynamics

Elaine A. Chandler, Gordon Baym

Kurt Alfred Georg Mendelssohn

Yosuke Ono, Ryohei Sakamoto, 弘之 森 +1 more

We study the sound modes of a Bose–Fermi mixture superfluid at finite temperatures in the collisional hydrodynamic regime. We extend Landau’s hydrodynamic theory to deal with a Bose–Fermi mixture superfluid and show the existence of three sound modes. We calculate the hydrodynamic sound velocities numerically using the Nozières and Schmitt-Rink theory at unitarity. The three-sound-modes hybrid in Bose–Fermi mixture superfluids contrasts with the two sound modes exhibited by 3He and 4He superfluids.

Yosuke Ono, Rei Hatsuda, Kenta Shiina +2 more

We study sound propagation in a Bose–Fermi superfluid mixture at finite temperatures. Sound modes in the mixture are described by the extended Landau's hydrodynamic theory. Our extended Landau's hydrodynamic theory shows that three sound modes exist. We calculate the hydrodynamic sound velocities and weights in the density response function based on the approach of Noziéres and Schmitt-Rink for the BCS to Bose–Einstein condensation crossover. In a Bose–Fermi superfluid mixture, the three sound mode pulses can be excited with an appreciable amplitude by density perturbations.

Satoru Konabe, Tetsuro Nikuni

Starting from an effective action for the order parameter field, we derive a coupled set of generalized hydrodynamic equations for a Bose condensate in an optical lattice at finite temperatures. Using the linearized hydrodynamic equations, we study the microscopic mechanism of the Landau instability due to the collisional damping process between condensate and noncondensate atoms. It is shown that the Landau criterion of the superfluidity for the uniform system is modified due to the presence of the periodic optical lattice potential. 1.