Superconducting junction with tri-component pairing gap functions

TL;DR

This paper investigates a superconducting hetero-junction with unconventional chiral p-wave and conventional s-wave gaps, revealing frustrated phase relationships and an anisotropic magnetoelectric effect at the interface.

Contribution

It introduces a Ginzburg-Landau free energy analysis of phase frustration and predicts an anisotropic spin magnetization along the junction edge.

Findings

Frustrated phase pattern characterized by complex gap functions.

Presence of anisotropic spin magnetization at the junction edge.

Analytical description of phase relationships in the hetero-junction.

Abstract

We study a superconducting hetro-junction with one side characterized by the unconventional chiral $p$-wave gap function $p_x\pm ip_y$ and the other side the conventional $s$-wave one. Though a relative phase of $\pm \frac{\pi}{2}$ between any two components of gap functions is favored in the junction region, mutual phase differences cannot achieve $\pm \frac{\pi}{2}$ simultaneously, which results in frustration. Based on a Ginzburg-Landau free energy analysis, the frustrated pattern is determined to be $s+ i\eta_1 (e^{ i\eta_2 \varphi/2}p_x +\eta_3 e^{- i\eta_2 \varphi/2}p_y)$ with $\eta_j=\pm 1$ ($j=1,2,3$), where $\varphi$ is the phase difference between the $p_x$- and $p_y$-wave gap functions. Furthermore, we find that the junction exhibits an anisotropic magnetoelectric effect, manifesting itself as an anisotropic spin magnetization along the edge of the junction.