Magnetism-driven unconventional effects in Ising superconductors: Role of proximity, tunneling, and nematicity
Darshana Wickramaratne, Menashe Haim, Maxim Khodas, I. I. Mazin
Abstract
Hybrid Ising superconductor-ferromagnetic insulator heterostructures provide a unique opportunity to explore the interplay between proximity-induced magnetism, spin-orbit coupling, and superconductivity. Here we use a combination of first-principles calculations of ${\mathrm{NbSe}}_{2}/{\mathrm{CrBr}}_{3}$ heterostructures and an analytical theory of Ising superconductivity to analyze the existing experiments and provide a complete explanation of highly nontrivial and largely counterintuitive effects: an increase in the magnitude of the superconducting gap accompanied by the broadening of the tunneling peaks; hysteretic behavior of the tunneling conductance that sets in $\ensuremath{\approx}2$ K below ${T}_{c}$; and nematic symmetry breaking in the superconducting state. The microscopic reason in all three cases appears to be the interplay between the proximity-induced exchange splitting and intrinsic defects. Finally, we predict additional interesting effects that at the moment cannot be addressed experimentally: spin-filtering when tunneling across ${\mathrm{CrBr}}_{3}$ and tunneling ``hot spots'' in momentum space that are anticorrelated with regions where the spin-orbit splitting is maximum.