Giant oscillations of the density of states and the conductance in a ferromagnetic conductor coupled to two superconductors

Kadigrobov, A.; Shekhter, R. I.; Jonson, M.

Giant oscillations of the density of states and the conductance in a ferromagnetic conductor coupled to two superconductors

Authors

Kadigrobov, A.

Shekhter, R. I.

Jonson, M.

Description

Giant oscillations of the density of electronic states and the differential conductance of a superconductor-ferromagnet-superconductor structure are predicted for the case when the exchange energy, $I_0$, due to the interaction between the electron spin and the spontaneous moment of the ferromagnet is smaller than the superconductor energy gap, $Δ$. The effect is due to the extremely large degeneration of the energy level $ε= I_0$ when the superconductor phase difference $ϕ$ is close to odd multiple of $π$ ($ε$ is the electron energy measured from the Fermi-energy). This quantum interference effect persists even in long ferromagnetic bridges whose length much exceeds the ''magnetic length'' ($\hbar v_{F}/I_{0}$ in the ballistic regime and $\sqrt{\hbar D/I_0}$ in the diffusive regime; $D$ is the electron diffusion constant). The predicted effect allows a direct spectroscopy of Andreev levels in the ferromagnet as well as a direct measurement of the exchange energy,$I_0$.
16 pages, 8 figures