Spinor condensate of 87Rb as a dipolar gas

Tomasz Świsłocki, Mirosław Brewczyk, Mariusz Gajda, Kazimierz Rzążewski

We consider a spinor condensate of 87Rb atoms in F=1 hyperfine state confined in an optical dipole trap. Putting initially all atoms in m_F=0 component we find that the system evolves towards a state of thermal equilibrium with kinetic energy equally distributed among all magnetic components. We show that this process is dominated by the dipolar interaction of magnetic spins rather than spin mixing contact potential. Our results show that because of a dynamical separation of magnetic components the spin mixing dynamics in 87Rb condensate is governed by dipolar interaction which plays no role in a single component rubidium system in a magnetic trap.

arxiv.org 0901.1763

Elementary excitations of a two-component Fermi system using the atomic-orbital approach

Tomasz Świsłocki, Tomasz Karpiuk, and Miroslaw Brewczyk

We investigate the ground state properties of normal and superfluid phases of a mixture of Fermi atoms at zero temperature in a quasi-one-dimensional harmonic trap. Assuming pairing occurs in the Hartree-Fock single-particle states (obtained using atomic orbitals approach) we calculate the spectrum of elementary excitations of the system. We find that for strong enough attraction between different kinds of fermions the state consisting of Cooper pairs becomes energetically favorable. For even stronger attraction a discontinuity located at the Fermi surface appears in the spectrum of elementary excitations. At the same time the chemical potential changes its sign and the system goes from the gas of Cooper pairs to the condensed phase of molecular dimers realizing the BCS to Bose-Einstein condensate crossover in one-dimensional space.

Phys. Rev. A 77, 033603 (2008)