Fulde–Ferrell–Larkin–Ovchinnikov State in Perpendicular Magnetic Fields in Strongly Pauli-Limited Quasi-Two-Dimensional Superconductors

We examine the Fermi-surface effect called nesting for Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state in strongly Pauli-limited quasi-two-dimensional superconductors, focusing on of three-dimensional factors, such as interlayer electron transfer, pairing, and off-plane magnetic fields including those perpendicular to most conductive layers (hereinafter fields). systems with a large Maki parameter so that orbital pair-breaking is negligible, except locking direction FFLO vector q magnetic-field direction. It known can be strong quasi-low-dimensional which suppressed by applying field parallel layers. Hence, it has sometimes been suggested may hardly enhance stability fields. illustrate that, contrary this view, stabilize well when tz small Fermi surfaces are open kz-direction, where denotes transfer energy. In particular, states. For example, cylindrical warped ≠ 0, states Δk ∝ sin kz exhibit μeHc ≈ 1.65Δα0 fields, much larger than typical values = Δs0 s-wave 1.28Δd0 d-wave 0. Here, μe Hc moment upper critical at T respectively, \(\Delta _{\alpha 0} \equiv 2\omega _{\text{c}}e^{ - 1/\lambda }}\). discuss possible relevance high-field superconducting phases observed compounds CeCoIn5 FeSe, candidates state. The present result could potentially provide physical reason fact areas phase diagrams occupied same order.