(a) Tc versus in-plane H of a Cr1/3NbS2/NbS2 device, Tc,bi(H), determined from R(T) curves in Fig. 2(b) for H upsweep (blue curve) and downsweep (red curve). The lower and upper sketches show the magnetic configuration of Cr1/3NbS2 for H < Hsat and H > Hsat, respectively. (b) Theoretical Tc,bi(H) for a S/F with a helimagnet becoming ferromagnetic at Hsat (blue curve) and for S/F with a homogeneous ferromagnet (red curve). The theoretical model used is shown in the lower panel, while the upper inset shows the decay of pairing amplitudes from the S/F interface in the F helimagnetic state: spin singlets (F0), long-ranged triplets (F2), and short-ranged triplets (F3).

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

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 demonstrated based on studies done on thin-film multilayers, 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 (vdW) stacks of flakes of the NbS2 combined with flakes of Cr1/3NbS2, 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 heterostructures is strongly dependent on the magnetic state of Cr1/3NbS2, 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 Cr1/3NbS2/NbS2 vdW interface.

A. Spuri, D. Nikolić, S. Chakraborty, M. Klang, H. Alpern, O. Millo, H. Steinberg, W. Belzig, E. Scheer, and A. Di Bernardo
Phys. Rev. Res. 6, 1 (2024)