Observation of a persistent non-equilibrium state in cold atoms

Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap

“…[29] it was shown that anharmonic corrections to the trap geometry were likely responsible for the anomalous exponential damping of the monopole mode observed above the critical temperature [26]. As shown in Ref.…”

“…As shown in Ref. [26], this damping is < 0.2 s −1 for clouds with a full width at half maximum (FWHM) of < 125 μm. In this work, the FWHM of the cloud below the critical temperature satisfies this criterion; thus, we neglect anharmonic corrections to the trap geometry as the observed damping rate is approximately an order of magnitude larger.…”

“…In earlier measurements described in Ref. [26], data were also taken along the xy plane, but technical difficulties were encountered with the imaging system along this axis during the course of the experiments discussed here. However, the limited data available from the xy plane suggests that the cloud was highly symmetric [27].…”

“…The experimental procedure parallels that of Ref. [26]-beginning from a system at equilibrium, the trap frequency is sinusoidally modulated at a driving frequency ω D ≈ 2π × 18-19 Hz for four periods with an amplitude ≈ 0.1:…”

“…The end result is an isotropic harmonic trap with ω 0 ≡ ω r = ω z = 2π × [9.03(2) Hz] with a residual asphericity of less than 0.2%. This system was used in previous work to study the monopole mode of a Bose gas above the BEC critical temperature [26], and a detailed description of the apparatus can be found in Ref. [27].…”