Why measured cold-atom mobility edges in 3D speckle disagree with numerics · revision history
Revision 1
Accepted · first revision · record
- Title
- Why measured cold-atom mobility edges in 3D speckle disagree with numerics
- Plain
- Atoms released into a random pattern of laser light (speckle) can be trapped by disorder if their energy is below a threshold, the mobility edge. The measured thresholds lie well above the values computed for the same disorder.
- Precise
- Noninteracting atoms (spin-polarized K-40 fermions, K-39 at zero scattering length, dilute Rb-87 BEC) in a 3D laser speckle potential of strength $V_R$ and correlation length $\sigma$, with correlation energy $E_\sigma = \hbar^2/(m \sigma^2)$. Measured mobility edges $E_c(V_R)$ (Kondov 2011, Jendrzejewski 2012, Semeghini 2015) disagree with transfer-matrix and scaling numerics (Delande and Orso 2014), the measured values lying higher by large factors. An answer is either an energy-resolved measurement (narrow energy distribution, calibrated energy shift from loading) agreeing with numerics, or the identified missing physics (energy distribution after loading, residual interactions, finite observation time).
- Settled by
- A measurement of $E_{c}$ with atoms prepared in a narrow, independently calibrated energy band in the speckle, compared with numerics for the exact speckle geometry.
- Kind
- phenomenon
- Answer type
- mechanism
- References
- (empty)
- Literature status
- open
- Status note
- Pasek, Orso and Delande (PRL 2017) showed that speckle anisotropy cannot explain the gap and that $E_{c}$ obeys universal scaling; no later measurement closing the gap is known to this compilation.
- Posed since
- 2014