Topological transitions in a model for proximity-induced superconductivity

Abstract

Using a prototype model for proximity induced superconductivity on a bilayer square lattice, we show that interlayer tunneling can drive change in topology of the Bogoliubov quasiparticle bands. Starting with topologically trivial superconductors, transitions to a non-trivial px + ipy state and back to another trivial state are discovered. We characterize these phases in terms of edge-state spectra and Chern indices. We show that these transitions can also be controlled by experimentally viable control parameters, the bandwidth of the metallic layer and the gate potential. Insights from our results on a simple model for proximity induced superconductivity may open up a new route to discover topological superconductors.

Pairing symmetries in the Zeeman-coupled extended attractive Hubbard model

“…So far we have classified these superconducting states in terms of opposite spin pairing (OSP) and equal spin pairing (ESP) states, leading to a description of minimum energy solutions in terms of pure singlet, pure triplet, and mixed-parity superconducting states. While, the main classification is done based on the nature of the spin state of the system we do mention different pairing symmetries, such as s -wave, -wave, -wave and -wave to define the nature of the orbital part of the gap function 51 , 52 . In the case of pure singlet, or pure triplet phase the nature of the orbital part can be easily understood, while for mixed-parity states such a separation does not exist.…”

Superconducting Kondo phase in an orbitally separated bilayer

“…Indeed, such strategy has proved fruitful, for instance, in the case of Ce-based superlattices [26], and more recently in the twisted bilayer graphene [27,28], which revealed a wealth of interesting magnetic and superconducting phenomena. We should mention that proximity effects have been studied in the context of the Hubbard model in a layered geometry [29,30], resulting in an induced pairing in the adjacent layers; electron-phonon coupling could also provide the appearance of superconductivity in Kondo insulators, by combining the Holstein model with the PAM [31][32][33].…”