Heikkinen P J, Casey A, Levitin L V, Rojas X, Vorontsov A, Sharma P, Zhelev N, Parpia J M, Saunders J
Department of Physics, Royal Holloway University of London, Surrey, UK.
Department of Physics, Montana State University, Bozeman, MT, USA.
Nat Commun. 2021 Mar 10;12(1):1574. doi: 10.1038/s41467-021-21831-y.
Superfluid He, with unconventional spin-triplet p-wave pairing, provides a model system for topological superconductors, which have attracted significant interest through potential applications in topologically protected quantum computing. In topological insulators and quantum Hall systems, the surface/edge states, arising from bulk-surface correspondence and the momentum space topology of the band structure, are robust. Here we demonstrate that in topological superfluids and superconductors the surface Andreev bound states, which depend on the momentum space topology of the emergent order parameter, are fragile with respect to the details of surface scattering. We confine superfluid He within a cavity of height D comparable to the Cooper pair diameter ξ. We precisely determine the superfluid transition temperature T and the suppression of the superfluid energy gap, for different scattering conditions tuned in situ, and compare to the predictions of quasiclassical theory. We discover that surface magnetic scattering leads to unexpectedly large suppression of T, corresponding to an increased density of low energy bound states.
具有非常规自旋三重态p波配对的超流氦为拓扑超导体提供了一个模型系统，拓扑超导体因其在拓扑保护量子计算中的潜在应用而引起了广泛关注。在拓扑绝缘体和量子霍尔系统中，由体态-表面对应和能带结构的动量空间拓扑产生的表面/边缘态是稳健的。在此，我们证明，在拓扑超流体和超导体中，依赖于涌现序参量的动量空间拓扑的表面安德列夫束缚态相对于表面散射的细节是脆弱的。我们将超流氦限制在高度D与库珀对直径ξ相当的腔内。对于原位调节的不同散射条件，我们精确测定了超流转变温度T和超流能隙的抑制情况，并与准经典理论的预测进行了比较。我们发现，表面磁散射导致T出现意外的大幅抑制，这对应于低能束缚态密度的增加。
