Rotational symmetry breaking and partial Majorana corner states in a high-Tc superconductor based heterostructure

TL;DR

This paper theoretically investigates how proximity to a high-Tc superconductor induces symmetry-breaking and Majorana corner states in a 2D topological insulator, revealing unique edge and corner quasiparticle phenomena.

Contribution

It introduces a microscopic model showing how mixed singlet and triplet pairing induce rotational symmetry breaking and Majorana corner states in TI-superconductor heterostructures.

Findings

C4 rotational symmetry breaking of energy bands and spectra.

Zero energy edge states localized at the upper boundary in cylindrical geometry.

Emergence of Majorana bound states at lower corners in finite systems.

Abstract

Applying a microscopic model, we study theoretically the quasiparticle excitation of a twodimensional topological insulator (TI) being in proximity to a high-Tc superconductor. In the momentum space, the proximity induced pairing term in the TI layer includes both the singlet channel and triplet channel, leading to the C4 rotational symmetry breaking of the energy bands and the quasiparticle spectra. For a cylinder geometry, the zero energy edge states may appear but they are localized at the upper boundary. For the finite-size system with open boundaries, the zero energy states at the upper boundary disappear and the Majorana bound states emerge at the two lower corners. All of the results can be understood well through exploring the pairing order parameter and the anomalous Green's function.