Fulde-Ferrell-Larkin-Ovchinnikov pairing induced by a Weyl nodal line in an Ising superconductor with a high critical field
Xiaoming Zhang, Feng Liu
Abstract
Superconductivity and electron topology are two quantum phenomena that have attracted much interest, but no causal relationship between them has been reported because superconductivity is a many-body effect due to electron-electron interaction, while electron topology is a single-particle manifestation of electron states. Here, we demonstrate that electron topology can induce Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing in Ising Bardeen-Cooper-Schrieffer (IBCS) superconductors. Specifically, we predict that the nonmagnetic metals of the ${MA}_{2}{Z}_{4}$ family, including ${\ensuremath{\alpha}}_{1}\text{\ensuremath{-}}{\mathrm{TaSi}}_{2}{\mathrm{P}}_{4}, {\ensuremath{\alpha}}_{1}\text{\ensuremath{-}}{\mathrm{TaSi}}_{2}{\mathrm{N}}_{4}, {\ensuremath{\alpha}}_{2}\text{\ensuremath{-}}{\mathrm{TaGe}}_{2}{\mathrm{P}}_{4}, {\ensuremath{\alpha}}_{1}\text{\ensuremath{-}}{\mathrm{NbSi}}_{2}{\mathrm{P}}_{4}$, and ${\ensuremath{\alpha}}_{2}\text{\ensuremath{-}}{\mathrm{NbGe}}_{2}{\mathrm{P}}_{4}$ monolayers, are all IBCS superconductors with a transition temperature ranging from a few to tens of degrees Kelvin. The intrinsic IBCS pairing alone will enhance the in-plane critical field ${B}_{\mathrm{c}}$ to \ensuremath{\sim}20--60 times the Pauli limit ${B}_{\mathrm{p}}$, and the extrinsic FFLO pairing evoked by topological Weyl nodal lines under a magnetic field can further double the ${B}_{\mathrm{c}}/{B}_{\mathrm{p}}$ ratio. Our findings not only enrich the fundamental relationship between superconductivity and electron topology, but they also yield an effective approach to enhance the robustness of superconductivity.