Vasenko A S, Golubov A A, Silkin V M, Chulkov E V
National Research University Higher School of Economics, 101000 Moscow, Russia.
J Phys Condens Matter. 2017 Jul 26;29(29):295502. doi: 10.1088/1361-648X/aa75c3. Epub 2017 May 30.
We study the effect of the Fermi surface anisotropy on the odd-frequency spin-triplet pairing component of the induced pair potential. We consider a superconductor/ ferromagnetic insulator (S/FI) hybrid structure formed on the 3D topological insulator (TI) surface. In this case three ingredients ensure the possibility of the odd-frequency pairing: (1) the topological surface states, (2) the induced pair potential, and (3) the magnetic moment of a nearby ferromagnetic insulator. We take into account the strong anisotropy of the Dirac point in topological insulators when the chemical potential lies well above the Dirac cone and its constant energy contour has a snowflake shape. Within this model, we propose that the S/FI boundary should be properly aligned with respect to the snowflake constant energy contour to have an odd-frequency symmetry of the corresponding pairing component and to insure the Majorana bound state at the S/FI boundary. For arbitrary orientation of the boundary, the Majorana bound state is absent. This provides a selection rule to the realization of Majorana modes in S/FI hybrid structures, formed on the topological insulator surface.
我们研究了费米面各向异性对诱导配对势奇数频率自旋三重态配对分量的影响。我们考虑在三维拓扑绝缘体（TI）表面形成的超导体/铁磁绝缘体（S/FI）混合结构。在这种情况下，有三个因素确保了奇数频率配对的可能性：（1）拓扑表面态，（2）诱导配对势，以及（3）附近铁磁绝缘体的磁矩。当化学势远高于狄拉克锥且其等能轮廓呈雪花形状时，我们考虑了拓扑绝缘体中狄拉克点的强各向异性。在该模型中，我们提出S/FI边界应相对于雪花等能轮廓适当对齐，以具有相应配对分量的奇数频率对称性，并确保在S/FI边界处存在马约拉纳束缚态。对于边界的任意取向，马约拉纳束缚态不存在。这为在拓扑绝缘体表面形成的S/FI混合结构中实现马约拉纳模式提供了一个选择规则。
