Department of Physics, QSO-Centre for Quantum Science, and Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, 730 Cumberland Street, Dunedin, 9016, New Zealand.
Joint Quantum Institute and Centre for Quantum Information and Computer Science, National Institute of Standards and Technology and University of Maryland, Gaithersburg, MD, 20899, USA.
Nat Commun. 2017 Sep 6;8(1):452. doi: 10.1038/s41467-017-00458-y.
Ultracold atomic gases have realized numerous paradigms of condensed matter physics, where control over interactions has crucially been afforded by tunable Feshbach resonances. So far, the characterization of these Feshbach resonances has almost exclusively relied on experiments in the threshold regime near zero energy. Here, we use a laser-based collider to probe a narrow magnetic Feshbach resonance of rubidium above threshold. By measuring the overall atomic loss from colliding clouds as a function of magnetic field, we track the energy-dependent resonance position. At higher energy, our collider scheme broadens the loss feature, making the identification of the narrow resonance challenging. However, we observe that the collisions give rise to shifts in the center-of-mass positions of outgoing clouds. The shifts cross zero at the resonance and this allows us to accurately determine its location well above threshold. Our inferred resonance positions are in excellent agreement with theory.Studies on energy-dependent scattering of ultracold atoms were previously carried out near zero collision energies. Here, the authors observe a magnetic Feshbach resonance in ultracold Rb collisions for above-threshold energies and their method can also be used to detect higher partial wave resonances.
超冷原子气体实现了许多凝聚态物理的范例，其中相互作用的控制主要得益于可调谐的费希巴赫共振。到目前为止，这些费希巴赫共振的特性几乎完全依赖于近零能量阈附近的实验来确定。在这里，我们使用基于激光的碰撞器在阈上探测铷的窄磁费希巴赫共振。通过测量碰撞云团的整体原子损耗作为磁场的函数，我们跟踪了能量相关的共振位置。在更高的能量下，我们的碰撞器方案会使损耗特征变宽，从而使得窄共振的识别变得具有挑战性。然而，我们观察到碰撞导致了出射云团质心位置的偏移。偏移量在共振处穿过零，这使得我们能够在阈上很好地准确确定其位置。我们推断的共振位置与理论非常吻合。先前在近零碰撞能量下进行了超冷原子能量相关散射的研究。在这里，作者观察到超冷 Rb 碰撞中的磁费希巴赫共振在阈上能量，并提出的方法也可用于探测更高的部分波共振。
