Confinement-Induced Resonances in Low-Dimensional Quantum Systems

Abstract

We report on the observation of confinement-induced resonances in strongly interacting quantum-gas systems with tunable interactions for one- and two-dimensional geometry. Atom-atom scattering is substantially modified when the s-wave scattering length approaches the length scale associated with the tight transversal confinement, leading to characteristic loss and heating signatures. Upon introducing an anisotropy for the transversal confinement we observe a splitting of the confinement-induced resonance. With increasing anisotropy additional resonances appear. In the limit of a two-dimensional system we find that one resonance persists.

Confinement-induced resonances in anharmonic waveguides

“…If there is no rotational symmetry, this degeneracy is broken, leading to the possibility of multiple resonances. Experimentally there is more than one resonance in the recent Innsbruck exper-iment [23]. Due to the similarity with the HCIR predictions [15], these were initially identified as conventional harmonic CIR resonances, corresponding to excitations of internal degrees of freedom.…”

“…In recent bosonic experiments on ultracold 137 Cs at Innsbruck [23], a strong, transversely anisotropic quasi-1D confinement is used to create an initially strongly repulsive (a 3D > 0) Tonks gas. This is followed by a sudden change in B-field to a new value, resulting in a molecular loss signature for a resonance which is confinement dependent.…”

“…In the recent Innsbruck Cs experiment with a quasi-1D geometry [23], two or more resonances were observed as the transverse confinement became more and more anisotropic. For a quasi-2D geometry, some experiments have observed 2D resonances on the attractive side with a 3D < 0 [24], while others have resonances on the repulsive side with a 3D > 0 [23,25]. Both the observation of multiple resonances and 2D resonances with repulsive interactions are in disagreement with standard HCIR predictions [20][21][22].…”

Engineering p-wave interactions in ultracold atoms using nanoplasmonic traps

“…For a value of ho z /e ¼ 10 3 , it produces a resonant behaviour for values of the transverse confinement l z B0.4|a 3D |. Such confinement-induced resonance behaviour has been observed in experiments with optical traps by increasing the scattering length by means of Feshbach resonances [29][30][31] . This procedure, in particular if an optical Feshbach resonance is involved, suffers from severe loss processes.…”

“…28. This contribution can be enhanced, thanks to the resonant behaviour of the atom-atom scattering length in strongly confined 2D settings 9,10 as demonstrated recently in ultracold atomic systems [29][30][31] . This not only allows to strengthen the interaction but also to explore both attractive and repulsive p-wave interactions, that is, going from the physics of p-wave pairing to fractional quantum Hall physics.…”