Signature of long-ranged spin triplets across a two-dimensional superconductor/helimagnet van der Waals interface

TL;DR

This study demonstrates the generation of long-range spin-triplet Cooper pairs across a two-dimensional superconductor/helimagnet interface, using van der Waals heterostructures of NbS2 and Cr1/3NbS2, with magnetic inhomogeneity controllable by an external field.

Contribution

First experimental evidence of long-ranged spin-triplet pairing in 2D superconductor/helimagnet van der Waals heterostructures, highlighting the role of magnetic inhomogeneity.

Findings

Critical temperature depends on magnetic state.

Magnetic inhomogeneity can be tuned with magnetic field.

Evidence of spin-triplet pairing across the interface.

Abstract

The combination of a superconductor with a magnetically inhomogeneous material has been established as an efficient mechanism for the generation of long-ranged spin-polarized (spin-triplet) Cooper pairs. Evidence for this mechanism, however, has been established based on studies done on three-dimensional systems, where the strong bonds existing at the interface between the superconductor and the magnetic material should in principle enhance proximity effects and strengthen any electronic correlations. Here, we fabricate devices based on van der Waals stacks of flakes of the two-dimensional superconductor $NbS_2$ combined with flakes of $Cr_{1/3}NbS_2$, which has a built-in magnetic inhomogeneity due to its helimagnetic spin texture at low temperatures. We find that the critical temperature of these vdW bilayers is strongly dependent on the magnetic state of $Cr_{1/3}NbS_2$, whose degree of magnetic inhomogeneity can be controlled via an applied magnetic field. Our results demonstrate evidence for the generation of long-ranged spin-triplet pairs across the $Cr_{1/3}NbS_2$/$NbS_2$ vdW interface.