Giant anisotropic magnetoresistance in Ising superconductor-magnetic insulator tunnel junctions

Superconductivity and magnetism are generally incompatible because of the opposing requirement on electron spin alignment. When combined, they produce a multitude of fascinating phenomena, including unconventional superconductivity and topological superconductivity. The emergence of two-dimensional (2D)layered superconducting and magnetic materials that can form nanoscale junctions with atomically sharp interfaces presents an ideal laboratory to explore new phenomena from coexisting superconductivity and magnetic ordering. Here we report tunneling spectroscopy under an in-plane magnetic field of superconductor-ferromagnet-superconductor (S/F/S) tunnel junctions that are made of 2D Ising superconductor NbSe2 and ferromagnetic insulator CrBr3. We observe nearly 100% tunneling anisotropic magnetoresistance (AMR), that is, difference in tunnel resistance upon changing magnetization direction from out-of-plane to inplane. The giant tunneling AMR is induced by superconductivity, particularly, a result of interfacial magnetic exchange coupling and spin-dependent quasiparticle scattering. We also observe an intriguing magnetic hysteresis effect in superconducting gap energy and quasiparticle scattering rate with a critical temperature that is 2 K below the superconducting transition temperature. Our study paves the path for exploring superconducting spintronic and unconventional superconductivity in van der Waals heterostructures.