Superconducting junction with tri-component pairing gap functions

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.