Current-voltage characteristics of the double tunnel junctions Co2CrAl–I–Pb/Sn–I–Pb under spin-polarized tunnel injection

Abstract

Current-voltage characteristics and existence features of a superconducting state under the action of tunneling injection of the spin-polarized current Iinj with a high spin polarization degree (p ≈ 0.97) were studied in double tunneling junctions ferromagnet-insulator-superconductor-insulator-superconductor Co2CrAl–I–Pb/Sn–I–Pb. An empirical formula was proposed for describing a dependence of the energy gap Δ on Iinj. A new spin-polarized inhomogeneous superconducting state consisting of superconducting and resistive regions was found. An existence of the proximity effect through a tunnel barrier between ferromagnetic and superconducting films was established. An effective recombination time of spin-polarized quasiparticles in the nonequilibrium superconductor Pb was estimated.

Current-voltage characteristics of low-resistance tunnel structures ferromagnet-insulator-superconductor Co2CrAl–I–Pb

“…In the low-resistance junctions Co 2 CrAl-I-Pb a proximity effect (PE) appears through a thin tunnel barrier between the ferromagnetic film Co 2 CrAl and the film of the superconductor Pb. 3 This leads to an additional mechanism for the destruction of the Cooper pairs in a near-barrier region, defined by the destruction parameter U, which changes in the energy range E D the density of states of elementary excitations of the superconductor N S (E) from that in the BCS, N T (E k ). 12 According to Ref.…”

“…1 it is seen that CVC of the junctions Co 2 CrAl-I-Pb and Sn-I-Pb are significantly different: in particular, the CVC of the F-I-S-junction are below those of the N-I-S-junction, the differential conductivity of the F-I-S-junction G FS < G NS at voltages V ( D/e (D % 1.34 meV is the energy gap of the superconductor Pb). 3,10 A variation of the differential conductance G NS and G FS3,10,11 can occur due to deviation of the electron density of elementary excitations in a superconductor, N S (E), in a near-barrier contact area from the density of states, according to the BCS theory N T (E k ), and due to change of the Fermi-Dirac distribution function f(E k ) of elementary excitations (see Eq. (1)).…”