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 ³He 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.

在存在各向同性间隙的情况下，费米子凝聚物的基态可以很好地防止扰动。承载安德列夫束缚态的间隙抑制区域、表面和涡核，似乎解除了这种严格的保护。在这里，我们表明，在超流体³ He 中，束缚态的作用更为微妙：当宏观物体在超流体中以超过朗道临界速度的速度运动时，几乎没有发生体积对断裂，而观察到的阻尼源自束缚覆盖移动物体的状态。我们确定了两个独立的时间尺度来控制束缚态动力学，其中之一比理论上预期的要长得多，并表明束缚态不与体激发相互作用。