The finite temperature Green's function technique is used to calculate the energies and damping rates of the elementary excitations of homogeneous, dilute, spin-1 Bose gases below the Bose-Einstein condensation temperature in both the density and spin channels. For this purpose a self-consistent dynamical Hartree-Fock model is formulated, which takes into account the direct and exchange processes on equal footing by summing up certain classes of Feynman diagrams. The model is shown to satisfy the Goldstone theorem and to exhibit the hybridization of one-particle and collective excitations correctly. The results are applied to gases of ${}^{23}\mathrm{Na}$ and ${}^{87}\mathrm{Rb}$ atoms.The finite temperature Green's function technique is used to calculate the energies and damping rates of the elementary excitations of homogeneous, dilute, spin-1 Bose gases below the Bose-Einstein condensation temperature in both the density and spin channels. For this purpose a self-consistent dynamical Hartree-Fock model is formulated, which takes into account the direct and exchange processes on equal footing by summing up certain classes of Feynman diagrams. The model is shown to satisfy the Goldstone theorem and to exhibit the hybridization of one-particle and collective excitations correctly. The results are applied to gases of ${}^{23}\mathrm{Na}$ and ${}^{87}\mathrm{Rb}$ atoms.

arXiv:cond-mat/0303424Physical Review AAug 29, 20037 citations

Excitations in a Dilute Condensed Bose Gas.

Pierre C. Hohenberg

Jan 1, 19620 citations

Lifetime of Single-Particle Excitations in a Dilute Bose–Einstein Condensate at Zero Temperature

Kazumasa Tsutsui, Takafumi Kita

We study the lifetime of single-particle excitations in a dilute homogeneous Bose-Einstein condensate at zero temperature based on a self-consistent perturbation expansion of satisfying Goldstone's theorem and conservation laws simultaneously.It is shown that every excitation for each momentum ${\bf p}$ should have a finite lifetime proportional to the inverse $a^{-1}$ of the $s$ -wave scattering length $a$ , instead of $a^{-2}$ for the normal state, due to a new class of Feynman diagrams for the self-energy that emerges upon condensation. We calculate the lifetime as a function of $|{\bf p}|$ approximately.We study the lifetime of single-particle excitations in a dilute homogeneous Bose-Einstein condensate at zero temperature based on a self-consistent perturbation expansion of satisfying Goldstone's theorem and conservation laws simultaneously.It is shown that every excitation for each momentum ${\bf p}$ should have a finite lifetime proportional to the inverse $a^{-1}$ of the $s$-wave scattering length $a$, instead of $a^{-2}$ for the normal state, due to a new class of Feynman diagrams for the self-energy that emerges upon condensation. We calculate the lifetime as a function of $|{\bf p}|$ approximately.

arXiv:1402.1196Journal of the Physical Society of JapanFeb 3, 20144 citations

Surface modes and vortex formation in dilute Bose-Einstein condensates at finite temperatures

Tapio Simula, Suvi Mirjami Virtanen, M.M. Salomaa

The surface mode spectrum is computed self-consistently for dilute Bose-Einstein condensates, providing the temperature dependence of the surface-mode-induced vortex nucleation frequency. Both the thermodynamic critical frequency for vortex stability and the nucleation frequency implied by the surface excitations increase as the critical condensation temperature is approached from below. The multipolarity of the destabilizing surface excitation decreases with increasing temperature. The computed finite-temperature critical frequencies support the experimental observations and the zero-temperature calculations for vortex nucleation.The surface mode spectrum is computed self-consistently for dilute Bose-Einstein condensates, providing the temperature dependence of the surface-mode-induced vortex nucleation frequency. Both the thermodynamic critical frequency for vortex stability and the nucleation frequency implied by the surface excitations increase as the critical condensation temperature is approached from below. The multipolarity of the destabilizing surface excitation decreases with increasing temperature. The computed finite-temperature critical frequencies support the experimental observations and the zero-temperature calculations for vortex nucleation.

arXiv:cond-mat/0204177Physical Review ASep 19, 200227 citations

{}^{23}\mathrm{Na}

and

{}^{87}\mathrm{Rb}

atoms.

{\bf p}

should have a finite lifetime proportional to the inverse

a^{-1}

of the

s

-wave scattering length

a

, instead of

a^{-2}

for the normal state, due to a new class of Feynman diagrams for the self-energy that emerges upon condensation. We calculate the lifetime as a function of

|{\bf p}|

approximately.