Quantum transport in noncentrosymmetric superconductors and thermodynamics of ferromagnetic superconductors

Abstract

We consider a general Hamiltonian describing coexistence of itinerant ferromagnetism, spin-orbit coupling and mixed spin-singlet/triplet superconducting pairing in the context of mean-field theory. The Hamiltonian is diagonalized and exact eigenvalues are obtained, thus allowing us to write down the coupled gap equations for the different order parameters. Our results may then be applied to any model describing coexistence of any combination of these three phenomena. As a specific application of our results, we consider tunneling between a normal metal and a noncentrosymmetric superconductor with mixed singlet and triplet gaps. The conductance spectrum reveals information about these gaps in addition to how the influence of spin-orbit coupling is manifested. We also consider the coexistence of itinerant ferromagnetism and triplet superconductivity as a model for recently discovered ferromagnetic superconductors. The coupled gap equations are solved self-consistently, and we study the conditions necessary to obtain the coexistent regime of ferromagnetism and superconductivity. Analytical expressions are presented for the order parameters, and we provide an analysis of the free energy to identify the preferred system state. Moreover, we make specific predictions concerning the heat capacity for a ferromagnetic superconductor. In particular, we report a nonuniversal relative jump in the specific heat, depending on the magnetization of the system, at the uppermost superconducting phase transition. [Shortened abstract due to arXiv submission.]

19 pages, 15 figures (high quality figures available in published version). Accepted for publication in Phys. Rev. B

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Cited by in corpus (7)

• Topological spin-current in non-centrosymmetric superconductors
• Surface bound states and spin currents in non-centrosymmetric superconductors
• Magnetic Properties in Non-centrosymmetric Superconductors with and without Antiferromagnetic Order
• Coexistence of itinerant ferromagnetism and a non-unitary superconducting state with line nodes: possible application to UGe${}_2$
• Nontrivial interplay between superconductivity and spin-orbit coupling in non-centrosymmetric ferromagnets
• Josephson Effect between Conventional and Rashba Superconductors
• Density of states near a vortex core in ferromagnetic superconductors: Application to STM measurements