Interplay of Superconductivity and Topological Order in HgTe Quantum Wells
Using the microscopic tight-binding equations we derive the effective Hamiltonian for the double-layer comprised of the two-dimensional topological insulator (TI) coupled to the s-wave isotropic superconductor (SC), and show that it contains terms describing mixing of the TI subband branches by the superconducting correlations induced by the proximity effect. We find that the proximity effect breaks down the rotational symmetry of the TI spectrum. We show that the edge states not only acquire the gap, as follows from the standard theory, but can also become localized by the Andreev-backscattering mechanism in a small coupling regime. In a strong coupling regime the edge states merge with the bulk states, and the TI transforms into an anisotropic narrow-gap semiconductor.
KeywordsTopological insulators Superconductivity
- 2.Qi, X., Zhang, S.-C.: arXiv:1008.2026v1