Local density of states in superconductor–strong ferromagnet structures

F. S. Bergeret; A. F. Volkov; K. B. Efetov

doi:10.1103/PhysRevB.65.134505

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Local density of states in superconductor–strong ferromagnet structures

F. S. Bergeret, A. F. Volkov, K. B. Efetov

DOI 10.1103/PhysRevB.65.134505 · Physical Review B

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Abstract

We study the dependence of the local density of states (LDOS) on coordinates for a superconductor-ferromagnet (S/F) bilayer and a S/F/S structure assuming that the exchange energy h in the ferromagnet is sufficiently large: hτ≫1, where τ is the elastic relaxation time. This limit cannot be described by the Usadel equation and we solve the more general Eilenberger equation. We demonstrate that, in the main approximation in the parameter (hτ)−1, the proximity effect does not lead to a modification of the LDOS in the S/F system and a nontrivial dependence on coordinates shows up in next orders in (hτ)−1. In the S/F/S sandwich the correction to the LDOS is nonzero in the main approximation and depends on the phase difference between the superconductors. We also calculate the superconducting critical temperature Tc for the bilayered system and show that it does not depend on the exchange energy of the ferromagnet in the limit of large h and a thick F layer.