Engineering momentum profiles of cold-atom beams

Abstract

We describe a procedure for engineering beams of cold atoms by selectively draining particles from a trapped gas based on momenta. Atoms escape through a filter potential that only transmits atoms with the desired momenta. We outline an algorithm that outputs a filter potential that produces a pre-specified beam momentum profile. We illustrate this procedure for the case of a narrow band-pass (NBP) quantum filter. Lastly, we discuss the application of the NBP filter for probing the self-energy and effective mass of Bose polarons, as well as the corresponding Landau criterion. arXiv:1903.11462v2 [cond-mat.quant-gas]

Impurity in a three-dimensional unitary Bose gas

“…[37] to the problem of impurity in a threedimensional unitary Bose gas at absolute zero. Such a mean-field-like treatments [38,39], regardless of their simplicity, were recently demonstrated [40][41][42][43] to be quite efficient for the description, in reasonable agreement with the Monte Carlo simulations [44,45] of Bose polarons in one dimension. In contrast to one-dimensional systems, where the effects of quantum fluctuations are strongly exhausted [46] a behavior of impurities in higher dimensions is known to be much influenced by the few-body physics.…”

Imaginary spin-orbital coupling in parity-time symmetric systems with momentum-dependent gain and loss

“…We consider a system of one-dimensional spin-1/2 cold atomic gas with the two spin components coupled by a laser field with Rabi frequency Ω. The momentum-dependent gain in the spin-↑ component can be realized by injecting spin-↑ atoms into the system using an atom laser with appropriate momentum distribution [72,74,75]. Especially, ref.…”

“…Especially, ref. [75] proposed a procedure to produce cold-atom beams with the Lorentzian profile of momentum distribution. And according to ref.…”

“…In cold atomic gas systems, the gain can be realized by injecting atoms into the condensate using an atom laser [72], while the loss can be realized by exciting atoms firstly to an excited state with a laser beam and then ejecting them out from the condensate via photon recoil [73]. Due to the momentum-distribution of the atom laser [74,75], and the Doppler effect in atom-light interaction [76], gain and loss realized in these ways have a distinct momentum-dependence. In the optical medium, spatially nonlocal gain and loss after a Fourier transformation are wavevector-dependent (or equivalently "momentum"-dependent) [77,78], and this feature has been proposed to explore the topological physics in photonic systems [79].…”

Mean-field study of repulsive 2D and 3D Bose polarons

“…Besides of explicit accounting for the external trapping potential and description of topologically non-trivial objects in dilute Bose condensates in low dimensions or restricted geometries, the MF was shown [4] to be useful in the Bose polaron problem. Being able to describe both the self-localization phenomenon [5][6][7][8][9][10] and translationinvariant [11] states of impurity by an appropriate choice of the wave function, the MF approximation was demonstrated [12][13][14] to be quite accurate analytical tool in the problem of one dimension (1D) Bose polaron. In recent years a single impurity atom immersed in Bose condensates have attracted much attention not least because of the experimental realization of 3D [15,16] Bose polarons.…”