Cooper pair induced frustration and nematicity of two-dimensional magnetic adatom lattices

Abstract: Apart from their potential for quantum computing, topological superconductors have instigated renewed interest in the intricate interplay between superconductivity and magnetic degrees of freedom. This question dates back to the 1950’ies, but the recent advances in material growth and custom made hybrid materials provide an exciting new perspective on this venerable problem. In this seminar, I will discuss a possible platform for frustrated magnetism utilizing a Cooper pair mediated long-ranged indirect exchange interaction in two-dimensional (2D) magnetic adatom lattices on s-wave superconducting surfaces. The competition between singlet electron correlations and the RKKY coupling is shown to lead to a variety of hidden-order states that break the point-group symmetry of the 2D adatom lattice at finite temperature. The phase diagram is constructed using a newly developed effective bond theory [3], and exhibits broad regions of long-range vestigial nematic order.

[1] Self-Organized Topological Superconductivity in a Yu-Shiba-Rusinov Chain, M. Schecter, K. Flensberg, M. H. Christensen, B. M. Andersen, J. Paaske, Phys. Rev. B 93, 140503 (2016)
[2] Spiral magnetic order and topological superconductivity in a chain of magnetic adatoms on a two-dimensional superconductor, M. H. Christensen, M. Schecter, K. Flensberg, B. M. Andersen, J. Paaske, Phys. Rev. B 94, 144509 (2016)
[3] Nematic Bond Theory of Heisenberg Helimagnets, Michael Schecter, Olav. F. Syljuåsen, J. Paaske, Phys. Rev. Lett. 119, 157202 (2017)
[4] Cooper Pair Induced Frustration and Nematicity of Two-Dimensional Magnetic Adatom Lattices, Michael Schecter, Olav F. Syljuåsen, Jens Paaske, Phys. Rev. B 97, 174412 (2018)