Giant oscillations of the density of states and the conductance in a ferromagnetic conductor coupled to two superconductors
msra(2005)
摘要
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, $\Delta$. The effect is due to the
extremely large degeneration of the energy level $\epsilon = I_0$ when the
superconductor phase difference $\phi$ is close to odd multiple of $\pi$
($\epsilon$ 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,$I_0$.
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关键词
density of state,superconductors,oscillations,energy levels,energy gap,quantum hall effect
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