Phase-Controlled Proximity-Effect in Ferromagnetic Josephson Junctions: Calculation of DOS and Electronic Specific Heat
Mohammad Alidoust, Jacob Linder, Gholamreza Rashedi, and Alse Sodbo
Phys. Rev. B 82, 014532 (2010). [PDF]We study the thermodynamic properties of a dirty ferromagnetic S∣F∣S Josephson junction with s-wave superconducting leads in the low-temperature regime. We employ a full numerical solution with a set of realistic parameters and boundary conditions, considering both a uniform and non-uniform exchange field in the form of a Bloch domain wall ferromagnetic layer. The influence of spin-active interfaces is incorporated via a microscopic approach. We mainly focus on how the electronic specific heat and density of states (DOS) of such a system is affected by the \textit{proximity effect}, which may be tuned via the superconducting phase difference. Our main result is that it is possible to \textit{strongly modify the electronic specific heat} of the system by changing the phase difference between the two superconducting leads from 0 up to nearly π at low temperatures. An enhancement of the specific heat will occur for small values h≃Δ of the exchange field, while for large values of h the specific heat is suppressed by increasing the phase difference between the superconducting leads. These results are all explained in terms of the proximity-altered DOS in the ferromagnetic region, and we discuss possible methods for experimental detection of the predicted effect.
