Gate-Tunable Superconducting Spin Valve in a van der Waals Ferromagnet/Superconductor/Ferromagnet Trilayer

Abstract

We theoretically demonstrate a gate-tunable superconducting spin valve effect (SVE) in a van der Waals (vdW) heterostructure composed of a monolayer superconductor (S) sandwiched between two ferromagnetic (F) monolayers (F/S/F). By electrostatically gating the ferromagnetic layers to modulate their chemical potentials, the system can be continuously tuned between the standard, inverse and triplet (non-monotonic) SVE regimes within the same device. This tunability originates from the gate-controlled hybridization between the superconducting and ferromagnetic electronic spectra, which determines the effective exchange field induced in the S-layer. Furthermore, we reveal that gating enables exotic, non-BCS temperature dependencies of the superconducting order parameter, including reentrant superconductivity, bistable states, first-order phase transitions, and the emergence of superconductivity at finite temperatures. Our results establish vdW F/S/F trilayers as a versatile and highly controllable platform for superconducting spintronics, where external gate voltages can selectively activate different spin-valve functionalities and unconventional superconducting states.