Magnetism-driven unconventional effects in Ising superconductors: role of proximity, tunneling, and nematicity

TL;DR

This paper investigates the complex effects of magnetism, proximity, and nematicity in Ising superconductors, combining first-principles calculations and analytical theory to explain experimental observations and predict new phenomena.

Contribution

It provides a comprehensive theoretical explanation for unconventional effects in Ising superconductors, highlighting the role of proximity-induced exchange and defects, and predicts novel spin-filtering and tunneling phenomena.

Findings

Superconducting gap increases with broadening of tunneling peaks.

Hysteretic tunneling conductance appears below 2 K below T_c.

Nematic symmetry breaking occurs in the superconducting state.

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 NbSe$_{2}$/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 $\approx 2$ 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 CrBr$_{3}$ and tunneling ``hot spots'' in momentum space that are anticorrelated with regions where the spin-orbit splitting is maximum.