Transitions between "$\pi$" and "0" states in superconductor -- ferromagnet -- superconductor junctions

TL;DR

This paper investigates the phase transitions between 0 and π states in superconductor-ferromagnet-superconductor junctions, analyzing how parameters like ferromagnet length, exchange field, and temperature influence the ground state, with a focus on the impact of system geometry and disorder.

Contribution

It provides a detailed phase diagram of SFS junctions showing the conditions for 0 and π states, highlighting the sensitivity to geometry and disorder effects.

Findings

Ground state depends on ferromagnet length, exchange field, and temperature.

Phase diagram shows regions of 0 and π states in parameter space.

System geometry and disorder significantly influence the phase transitions.

Abstract

Experimental and theoretical study of superconductor (S) -- ferromagnet (F) -- superconductor junctions showed that in certain range of parameters (e.g., the length of the ferromagnet $d_F$, the exchange field, $E_{\rm ex}$) the ground state of a SFS junction corresponds to superconducting phase difference $\pi$ or 0. The phase diagram of a SFS junction with the respect to $\pi$ and 0 states is investigated in this letter in $E_{\rm ex}, d_{F}, T$ space. It is shown that the phase diagram is very sensitive to the geometry of the system, in particular, to the amount of disorder.