Interplay between superconductivity and magnetism in a van-der-Waals NbSe2-CrSBr hybrid

Maya Klang, Shahar Simon, Yonathan Anahory, Oded Millo, and Hadar Steinberg
Racah Institute of Physics, Hebrew University Jerusalem, Israel

Recently, significant interest is attracted by the interplay between magnetic van-der-Waals (vdW) materials such as CrSBr and superconductors such as NbSe2. Here we study a 3-layer stack consisting of a WS2 tunnel barrier placed above a NbSe2 – CrSBr hybrid. NbSe2 is a transition metal dichalcogenide (TMD) superconductor which exhibits 2-band superconductivity in the bulk, and Ising spin-orbit protection at the thin limit, whereas CrSBr is a type-A layered antiferromagnet in which the magnetic coupling is ferromagnetic within each layer, and antiferromagnetic between adjacent layers. By tunnelling into the proximitized NbSe2, we measure the quasiparticle density of states while varying applied magnetic fields. Measuring at a base temperature of 20mK, we achieve fine spectral resolution, revealing an intricate structure in the NbSe2 spectrum. At zero applied magnetic field, the NbSe2 spectrum exhibits a single gap. We find that applied magnetic field has a surprising effect: a second gap appears as the field crosses zero, and is closed as the field scan is reversed. This is a hysteresis-like effect, exhibiting memory loss and a return to the zero-field state instead of magnetic memory. We suggest that the ferromagnet affects the two-band physics by either modifying inter-band coupling rates, or via intra-band depairing rates. In addition, it is likely that the 2nd gap is highly sensitive to the orbital fields emanating from the CrSBr flake and may also be more sensitive to magnetic proximity.

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