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 Center for Quantum Information and Computer Science, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20899, USA.
Nat Commun. 2016 Jul 11;7:12069. doi: 10.1038/ncomms12069.
The wavefunction for indistinguishable fermions is anti-symmetric under particle exchange, which directly leads to the Pauli exclusion principle, and hence underlies the structure of atoms and the properties of almost all materials. In the dynamics of collisions between two indistinguishable fermions, this requirement strictly prohibits scattering into 90° angles. Here we experimentally investigate the collisions of ultracold clouds fermionic (40)K atoms by directly measuring scattering distributions. With increasing collision energy we identify the Wigner threshold for p-wave scattering with its tell-tale dumb-bell shape and no 90° yield. Above this threshold, effects of multiple scattering become manifest as deviations from the underlying binary p-wave shape, adding particles either isotropically or axially. A shape resonance for (40)K facilitates the separate observation of these two processes. The isotropically enhanced multiple scattering mode is a generic p-wave threshold phenomenon, whereas the axially enhanced mode should occur in any colliding particle system with an elastic scattering resonance.
在粒子交换下，不可分辨费米子的波函数是反对称的，这直接导致了泡利不相容原理，从而构成了原子的结构和几乎所有材料的性质。在两个不可分辨费米子之间的碰撞动力学中，这一要求严格禁止散射成 90°角。在这里，我们通过直接测量散射分布来实验研究超冷费米子（40）K 原子的碰撞。随着碰撞能量的增加，我们用其明显的哑铃形状和没有 90°出射的特征来识别 p 波散射的维格纳阈值。在此阈值之上，多重散射的影响表现为偏离基本的二元 p 波形状，无论是各向同性地还是轴向地添加粒子。（40）K 的形状共振有助于分别观察这两个过程。各向同性增强的多重散射模式是一种通用的 p 波阈值现象，而轴向增强的模式应该出现在任何具有弹性散射共振的碰撞粒子系统中。
