Strongly parity-mixed superconductivity in the Rashba-Hubbard model

Recently, artificial superlattices containing strongly correlated electron systems, such as CeCoIn₅/YbCoIn_5, have been fabricated [1]. Rashba-type antisymmetric spin-orbit coupling (ASOC) arises from polar inversion symmetry breaking at the interface of heterostructures. Unique superconducting phases are expected to be realized there owing to the interplay of two-dimensional magnetic fluctuations and Rashba ASOC.
Motivated by these considerations, we study superconductivity in the Rashba-Hubbard model. We show that the Fermi surfaces (FSs) are robust against critical magnetic fluctuations in contrast to a previous theory [2]. Furthermore, we show that strongly parity-mixed superconductivity with dominant d-wave pairing is robust in contrast to the proposal in Ref. [3]. Interestingly, parity mixing is enhanced near the type-II van Hove singularity. We find signatures of the type-II van Hove singularity, such as strong instability to commensurate antiferromagnetic order, and the spin-triplet gap function changing from p-wave to f-wave [4].

[1] M. Shimozawa et al., Rep. Prog. Phys. 79, 074503 (2016).
[2] Y. Fujimoto et al., JPSJ 84, 043702 (2015).
[3] A. Greco and A. P. Schnyder, Phys. Rev. Lett. 120,177002 (2018).
[4] K. Nogaki and Y. Yanase, Phys. Rev. B 102, 165114(2020).