Mays R, Nikolić P
Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030, United States of America.
Institute for Quantum Matter at Johns Hopkins University, Baltimore, MD 21218, United States of America.
J Phys Condens Matter. 2023 Apr 3;35(24). doi: 10.1088/1361-648X/acc6b0.
Cooper pairing in ultrathin films of topological insulators, induced intrinsically or by proximity effect, can produce an energetically favorable spin-triplet superconducting state. The spin-orbit coupling acts as an SU(2) gauge field and stimulates the formation of a spin-current vortex lattice in this superconducting state. Here we study the Bogoliubov quasiparticles in such a state and find that the quasiparticle spectrum consists of a number of Dirac nodes pinned to zero energy by the particle-hole symmetry. Some nodes are 'accidental' and move through the first Brillouin zone along high-symmetry directions as the order parameter magnitude or the strength of the spin-orbit coupling are varied. At special parameter values, nodes forming neutral quadruplets merge and become gapped out, temporarily producing a quadratic band-touching spectrum. All these features are tunable by controlling the order parameter magnitude via a gate voltage in a heterostructure device. In addition to analyzing the spectrum at the mean-field level, we briefly discuss a few experimental signatures of this spectrum.
拓扑绝缘体超薄膜中由本征或近邻效应诱导的库珀对，可产生能量上有利的自旋三重态超导态。自旋轨道耦合起着SU(2)规范场的作用，并在这种超导态中刺激自旋流涡旋晶格的形成。在此，我们研究处于这种状态的博戈留波夫准粒子，发现准粒子能谱由一些通过粒子 - 空穴对称性固定在零能量的狄拉克节点组成。一些节点是“偶然的”，随着序参量大小或自旋轨道耦合强度的变化，它们沿着高对称方向穿过第一布里渊区。在特殊参数值下，形成中性四重态的节点合并并出现能隙，暂时产生二次能带接触能谱。所有这些特征都可通过在异质结构器件中通过栅极电压控制序参量大小来调节。除了在平均场水平分析能谱外，我们还简要讨论了该能谱的一些实验特征。
