Kanász-Nagy M, Glazman L, Esslinger T, Demler E A
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
Phys Rev Lett. 2016 Dec 16;117(25):255302. doi: 10.1103/PhysRevLett.117.255302.
We analyze the recently measured anomalous transport properties of an ultracold gas through a ballistic constriction [S. Krinner et al., Proc. Natl. Acad. Sci. U.S.A. 113, 8144 (2016)]. The quantized conductance observed at weak interactions increases severalfold as the gas is made strongly interacting, which cannot be explained by the Landauer theory of single-channel transport. We show that this phenomenon is due to the multichannel Andreev reflections at the edges of the constriction, where the interaction and confinement result in a superconducting state. Andreev processes convert atoms of otherwise reflecting channels into the condensate propagating through the constriction, leading to a significant excess conductance. Furthermore, we find the spin conductance being suppressed by superconductivity; the agreement with experiment provides an additional support for our model.
我们分析了最近测量的超冷气体通过弹道收缩区时的反常输运特性 [S. 克里纳等人，《美国国家科学院院刊》113, 8144 (2016)]。在弱相互作用下观察到的量子化电导，随着气体变为强相互作用而增加了几倍，这无法用单通道输运的朗道尔理论来解释。我们表明，这种现象是由于收缩区边缘的多通道安德烈夫反射，在那里相互作用和限制导致了超导态。安德烈夫过程将原本反射通道的原子转化为通过收缩区传播的凝聚态，从而导致显著的额外电导。此外，我们发现自旋电导被超导性抑制；与实验的吻合为我们的模型提供了额外的支持。
