Coexistence and tuning of spin-singlet and triplet transport in spin-filter Josephson junctions

Realization of 0 - $π$ states in SFIS Josephson junctions. The role of spin-orbit interaction and lattice impurities

“…To overcome this issue, π-JJs with a nonmetallic barrier result to be well suited for these kinds of applications. As matter of fact, transport properties through ferromagnetic insulator based JJs (SFIS JJs) have been investigated both theoretically [26,27] and experimentally [28], displaying temperature induced 0 − π transitions together with unconventional I c (T ) behaviors [29,30]. Therefore, the possibility to arrange an equilibrium superconducting phase difference of π across JJ has been theoretically predicted also in this case [26,31].…”

“…In this intriguing scenario, one of the most challenging issues is to find an effective way of controlling the occurrence of 0 − π transitions in SFIS JJs, through a direct action on their I c (T ) behavior. It is well known that tuning the exchange field of the barrier is an available technique to manipulate the critical current [30], thus driving the switching between 0, 0 − π and π regimes. However, this approach does not provide an easy engineering of ferromagnetic JJs based devices.…”

“…In this article, we study the Josephson effect in SFIS JJs using a 2D Bogolioubov de Gennes (BdG) tight-binding model [30,[35][36][37], where we include additional relevant effects, namely the presence of spin-orbit coupling (SOC), on-site ex-change field inhomogeneities and lattice impurities.…”

“…Therefore, we identify SFIS JJs as sources of unconventional odd-frequency superconductivity and equal-spin triplet pairings when spin-mixing (SOC) and disorder effects are involved [6,35,[38][39][40][41][42][43][44], confirming the results in Refs. [29,30].…”

“…In Sec. II we introduce our BdG model hamiltonian [30,35,36] and describe the recursive Green's function approach [36,37] used to calculate currents and correlation functions.…”