Unveiling Intrinsic Triplet Superconductivity in Noncentrosymmetric NbRe through Inverse Spin-Valve Effects

Abstract

NbRe is a non-centrosymmetric superconductor that has been proposed as a candidate for intrinsic spin-triplet pairing. However, a conclusive demonstration of triplet pairing in NbRe is yet to be found. To probe the presence of equal-spin triplet Cooper pairs, we fabricated Py/NbRe/Py trilayers capped with an antiferromagnetic layer. Magnetic and electrical measurements reveal an inverse spin-valve effect, which could indicate equal-spin triplet superconductivity. The minimal sample structure and the lack of ad hoc engineered interfaces clearly associate our observation to intrinsic triplet correlations of NbRe. The availability of NbRe in thin-film form and the simplicity of the heterostructure highlight its potential as a scalable platform for superconducting spintronics.

Figures (4)

• Figure 1: Structure of the Py/NbRe/Py/$\alpha$-Fe$_2$O$_3$ (F/S/F/AF) SV device in both (a) P and (b) AP alignment of the two Py layer magnetizations. A representation of equal-spin triplet Cooper pairs and their propagation into the F layers is also depicted.
• Figure 2: Normalized magnetic moment $m/m_s$ of NbRe-based SV as a function of the magnetic field measured at $T=2.5$ and 9 K. The AP and P magnetic moments alignment of the two Py layers are schematically reported at the fields where the transport properties were performed. The colored arrows represent the orientation of magnetic field.
• Figure 3: Superconducting resistive transitions of NbRe-based SV measured in both P and AP magnetic configurations. The magnetic field values and the associated SV magnetic configuration (P or AP) are indicated in the legends. The difference between the averaged AP and P transitions is shown in the inset. See text for details.
• Figure 4: (a) Normalized magnetic moment $m/m_s$ of Nb-based SV as a function of the magnetic field measured at $T=4$ and 9 K. The AP and P magnetic moments alignment of the two Py layers can be observed in the curve performed at $T=4$ K. (b) Superconducting resistive transitions of Nb-based SV measured in both P and AP magnetic configurations. The magnetic field values and the associated P and AP configurations are reported in the legends. The difference between the averaged AP and P transitions is reported in the inset.