1210.2546 (A. Moor et al.)

Realization of the $π$-state in junctions formed by multi-band
superconductors with a spin-density-wave    [PDF]

A. Moor, A. F. Volkov, K. B. Efetov

Using a simple model for Fe\nobreakdash-based pnictides, we calculate the Josephson current $I_{\text{J}}$ in a tunnel junction composed by such superconductors. We employ the tunnel Hamiltonian method and quasiclassical Green's functions. We study both the case of coexistence of the superconducting ($\Delta $) and magnetic (SDW---spin density wave) order parameters and the case when only the superconducting order parameter exists. We analyze ideal and nonideal nesting and show that the current $I_{\text{J}}$ depends on the mutual orientation of magnetization of the SDW only in the case of nonideal nesting. It is found that the realization of the $\pi$\nobreakdash-junction is possible in both cases. We show also that in $\text{S}_{++}/\text{I}/\text{S}_{+-}$ tunnel junctions an anomalous term $\sim I_{\text{an}} \cos \varphi$ may arise in the Josephson current and this result remains valid in the absence of the SDW ($\text{S}_{++}$ and $\text{S}_{+-}$ are superconductors with $(\Delta, \Delta)$ respectively $(\Delta, -\Delta)$ order parameters in different bands and $\text{I}$ denotes an insulating layer).

View original: http://arxiv.org/abs/1210.2546