The Joint Condensed Matter Seminar (JCMS) series is organised by KTH Royal Insitute of Technology, Nordita, and Stockholm University.
On Monday, October 26th, 2026 from 10:15 to 10:15 we will host a seminar by Hennadii Yerzhakov from Nordita.
Topological superconductivity and induced triplet pairing in the high-field vortex states of Rashba spin-orbit-coupled and s-wave centrosymmetric superconductors
I will start my talk by revisiting the scenario of the appearance of non-trivial topological superconductivity in 2D and 3D Rashba spin-orbit-coupled s-wave superconductors in an applied magnetic field, in particular, in the context of 3D ferroelectric superconductors, e.g., SrTiO3. First, I will show that in 3D for a uniform Zeeman field, two or four Majorana-Weyl cones emerge when the field exceeds a critical value. These Weyl cones can be tilted by tuning the angle between the ferroelectric polarization and the Zeeman field and may even “over-tilt” converting type-I Weyl points to type-II with Bogoliubov Fermi surfaces. I will also show that tetragonal domain walls can, in some cases, become interfaces between domains characterized by opposite Majorana-Weyl cones’ chiralities. Such domain walls will then host Majorana zero modes inside the specimen. To account for the realistic scenario, I will then consider the orbital effect of the magnetic field and show that single superconducting vortices are surrounded by topological “halos” hosting Majorana states on their outer boundaries and in their centers. As the value of the magnetic field increases, the density of the vortices grows, which might lead to the overlapping of the topological ``halos’’ and, eventually, to the percolation of the topological phase throughout the system.
If time permits, I will switch to a discussion of centrosymmetric s-wave superconductors and show that, in the presence of spin–orbit coupling, the Ginzburg–Landau description of centrosymmetric superconductors admits a Lifshitz-like invariant that is linear in spatial derivatives and couples the dominant singlet and subdominant triplet order parameters (OPs), such as s-wave and p-wave OPs. I will then discuss some possible physical consequences of this coupling, in particular, the induction of a p-wave superconducting OP in the vortex state of an s-wave superconductor.