Orbital FFLO and layer-selective FFLO phases in trilayer NbSe$_2$

TL;DR

This paper investigates the phase diagram of trilayer NbSe$_2$ under in-plane magnetic fields, revealing the existence of orbital and layer-selective FFLO phases through large-scale numerical calculations.

Contribution

It introduces the concept of a layer-selective FFLO phase in trilayer NbSe$_2$, expanding understanding of finite-momentum superconductivity in layered materials.

Findings

Identification of orbital FFLO phase in NbSe$_2$

Discovery of a layer-selective FFLO phase

Numerical phase diagram mapping under magnetic fields

Abstract

Finite-momentum superconductivity has become an important research topic in condensed matter physics. In particular, the orbital Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, which is stabi lized in atomically thin films by the orbital effect of an external magnetic field, has been getting attention as a fascinating finite-momentum superconducting state recently. We study the phase diagram of the trilayer Ising superconductor NbSe$_2$ in the in-plane magnetic field, taking into ac count the orbital effect, the paramagnetic effect, and the spin-orbit coupling. The finite-momentum gap structure in the high-field region is shown by a large-scale numerical calculation based on the Bogoliubov-de Gennes equation. We find an exotic superconducting phase, a layer-selective FFLO phase, in which finite-momentum Cooper pairs coexist with zero-momentum Cooper pairs, separated from the orbital FFLO phase.