Abstract: Topological superconductors are of high current interest due to their exceptional properties and potential for applications in quantum information technologies. As opposed to topological insulators, topological superconductors are by their very nature strongly interacting and are, at the same time, susceptible to disorder. To accurately account for the effects of disorder and interactions has, however, remained challenging, both in the theoretical descriptions and when interpreting the experimental data. To resolve these challenges, we introduce a new theoretical tool that combines functional renormalization group with a real-space mean-field analysis [1], capturing the essential features of topology, disorder, and interactions. In this talk, I will show how our approach uncovers the conditions under which topological superconductivity emerges in the simultaneous presence of electronic correlations, spin-orbit coupling, and singular density of states at van Hove singularities in two dimensions. Specifically, we find a cascade of different topological superconducting states, including the p-wave and d-wave states with first-order topology, and a p+id pairing exhibiting second-order topology. I will further show that while both the helical Majorana edge states in the p-wave superconductor and corner states in the p+id superconductor are robust to residual interactions and disorder, the flat-band Majorana states in the d-wave superconductor are unstable towards the formation of a phase crystal [2]. I will also discuss how van Hove singularities can act as generic platforms in the search for new topological quantum matter.

References:
[1] P. M. Bonetti*, D. Chakraborty*, X. Wu, A. P. Schnyder, arXiv:2304.07100 (2023). *=equal contribution.
[2] D. Chakraborty, T. Löfwander, M. Fogelström & A. M. Black-Schaffer, npj Quantum Materials 7, 44 (2022).

Meeting ID: 942 0086 9428
Passcode: 264064