Resonant dynamics of chromium condensates

Abstract

We numerically study the dynamics of a spinor chromium condensate in low magnetic fields. We show that the condensate evolution has a resonant character revealing rich structure of resonances similar to that already discussed in the case of alkali-atoms condensates. This indicates that dipolar resonances occur commonly in the systems of cold atoms. In fact, they have been already observed experimentally. We further simulate two recent experiments with chromium condensates, in which the threshold in spin relaxation and the spontaneous demagnetization phenomena were observed. We demonstrate that both these effects originate in resonant dynamics of chromium condensate.Comment: 8 pages, 9 figure

Spin distillation cooling of ultracold Bose gases

“…Higher spin states are reached through , with . At ultracold temperatures Bose enhancement favors processes that involve the condensate, but all-condensate transitions like those seen in 18 , 43 are ruled out by the Zeeman energy threshold. No condensates appear in components .…”

“…In the classical-field model the cloud is described by the seven-component spinor wave function with one component for each value of the spin projection along the direction of the applied magnetic field . It evolves according to the multicomponent Gross-Pitaevskii equation 43 : where the energy functional consists of three parts. The first one represents the single-particle term which includes the kinetic, potential , as well as Zeeman energies, in which .…”

“…( 1 ) describes the dipolar interactions. Since the spin projection of a pair of atoms colliding via dipolar forces can change at most by 2 and the spin projection of a single atom changes maximally by 1, the matrix becomes tridiagonal 43 . On the main diagonal one has .…”

“…Dipolar collisions allow for a change of the magnetization of the system 45 , 53 – 56 . In fact, transfer of atoms to components is possible only due to dipolar interactions 43 . Energies available in the cloud can surmount the Zeeman energy difference when the magnetic field magnitude is sufficiently low, making possible the population of higher Zeeman states.…”

Improving observability of the Einstein–de Haas effect in a rubidium condensate

“…In gaseous rubidium, the Einstein-de Haas effect becomes possible only because there exist resonances that amplify the transfer of atoms between dif-ferent Zeeman components [9,17]. It has been recently shown that dipolar resonances occur in chromium condensates [18] as well.…”