A “stripe” finite-momentum/FFLO phase in multi-layer Van der Waals superconductors*

Theoretical calculations using the Ginzburg Landau formalism have predicted that multi-layer systems produce, in the presence of an in plane magnetic field, superconducting states with finite momentum/FFLO pairing [1]. The presence of such states has been experimentally verified [2]. The Ginzburg-Landau theory, valid near T_c, assumes that the pairing momentum, q, is a constant. We have solved self-consistent gap equations to compute the pairing momentum and find that in general the pair momentum q varies in space. We compute the phase diagram to identify where these stripe-FFLO states occur as a function of inter-layer coupling, magnetic field, and temperature. We also discuss the experimental implications.

[1] Liu, C.-X. (2017). Unconventional Superconductivity in Bilayer Transition Metal Dichalcogenides. Physical Review Letters, 118(8), 087001. https://doi.org/10.1103/PhysRevLett.118.087001

[2] Wan, P., Zheliuk, O., Yuan, N. F. Q., Peng, X., Zhang, L., Liang, M., Zeitler, U., Wiedmann, S., Hussey, N. E., Palstra, T. T. M., & Ye, J. (2023). Orbital Fulde–Ferrell–Larkin–Ovchinnikov state in an Ising superconductor. Nature, 619(7968), 46–51. https://doi.org/10.1038/s41586-023-05967-z