Autti S, Ahlstrom S L, Haley R P, Jennings A, Pickett G R, Poole M, Schanen R, Soldatov A A, Tsepelin V, Vonka J, Wilcox T, Woods A J, Zmeev D E
Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK.
P.L. Kapitza Institute for Physical Problems of RAS, Moscow, 119334, Russia.
Nat Commun. 2020 Sep 21;11(1):4742. doi: 10.1038/s41467-020-18499-1.
The ground state of a fermionic condensate is well protected against perturbations in the presence of an isotropic gap. Regions of gap suppression, surfaces and vortex cores which host Andreev-bound states, seemingly lift that strict protection. Here we show that in superfluid He the role of bound states is more subtle: when a macroscopic object moves in the superfluid at velocities exceeding the Landau critical velocity, little to no bulk pair breaking takes place, while the damping observed originates from the bound states covering the moving object. We identify two separate timescales that govern the bound state dynamics, one of them much longer than theoretically anticipated, and show that the bound states do not interact with bulk excitations.
在存在各向同性能隙的情况下，费米子凝聚体的基态能很好地抵御微扰。能隙被抑制的区域、存在安德烈夫束缚态的表面和涡旋核心，似乎打破了这种严格的保护。在此我们表明，在超流氦中，束缚态的作用更为微妙：当一个宏观物体在超流中以超过朗道临界速度的速度移动时，几乎不会发生体对破坏，而观察到的阻尼源于覆盖在移动物体上的束缚态。我们确定了两个独立的时间尺度来支配束缚态动力学，其中一个比理论预期长得多，并表明束缚态不与体激发相互作用。
