Theoretical study of large proximity-induced s -wave-like pairing from a d -wave superconductor

We use the proximity effect to generate effective topological superconductors by placing metals with strong spin-orbit coupling in contact with a superconductor, aiming to produce Majorana zero modes useful for topologically protected quantum computation. In recent experiments, several quintuple layers of ${\text{Bi}}_{2}{\text{Se}}_{3}$ were epitaxially grown on the high-${T}_{c}$ material ${\text{Bi}}_{2}{\text{Sr}}_{2}{\text{CaCu}}_{2}{\text{O}}_{8+\ensuremath{\delta}}$, and conflicting experimental results were reported. We use the standard mean-field approach to study this heterostructure and find it is unlikely to have a large proximity-induced superconducting gap. Despite the seemingly correct temperature dependence, the $s$-wave gap claimed to be observed may not be purely superconducting in origin. Future work on the proximity-induced bulk superconducting gap and the interfacial band structure should shed light on this issue.