Anisotropic Josephson coupling of $d$ vectors in triplet superconductors arising from frustrated spin textures

TL;DR

This paper shows how noncollinear spin textures in frustrated magnetic systems can induce anisotropic Josephson couplings between triplet superconducting $d$ vectors, leading to novel phenomena like anomalous vortices and Josephson diode effects.

Contribution

It introduces a mechanism linking frustrated magnetism and triplet superconductivity, revealing how spatial spin textures influence superconducting pairing and transport properties.

Findings

Noncollinear spin textures generate spin triplet pairing correlations.

Anisotropic Josephson couplings can favor spatially varying superconducting order.

Predicted a Josephson diode effect proportional to spin chirality.

Abstract

We demonstrate that coupling itinerant electrons to a noncollinear classical exchange field can induce anisotropic Josephson coupling between superconducting $d$ vectors, analogous to the Dzyaloshinskii-Moriya and $\Gamma$-type interactions in magnetism. Using perturbative methods, we analyze an $s$-$d$ model on a geometrically frustrated lattice. Noncollinear local spin textures generate spin triplet pairing correlations and can favor spatially varying superconducting order due to anisotropic Josephson couplings between $d$ vectors, endowing a ``pliability'' to the pairing order that competes with the superfluid stiffness. For nonunitary pairing, this spatial texture of $d$ vectors can give rise to anomalous vortices in the absence of an external magnetic field. We further predict a Josephson diode effect with efficiency proportional to the spin chirality of the underlying magnetic texture. These results establish a link between frustrated magnetism and spatial textures of triplet superconducting pairing, with implications for a range of materials such as Mn$_3$Ge and $4H_b$-TaS$_2$, where superconductivity can be proximity-induced or intrinsic.