Superconducting spin filter |
N. M. Chtchelkatchev
L. D. Landau Institute for Theoretical Physics RAS, 117940 Moscow, Russia Institute for High Pressure Physics, Russian Academy of Sciences 142092 Troitsk, Moscow Region, Russia
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PACS: 74.50.+r, 74.80.Fp, 75.75.+a
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Abstract
Consider two normal leads coupled to a superconductor;
the first lead is biased while the second one and the
superconductor are grounded. In general, a finite current
I2(V1,0) is induced in the grounded lead 2; its magnitude
depends on the competition between processes of Andreev and normal
quasiparticle transmission from the lead 1 to the lead 2. It is
known that in the tunneling limit, when normal leads are weakly
coupled to the superconductor, I2(V1,0)=0, if |V1|<Δ
and the system is in the clean limit. In other words, Andreev and
normal tunneling processes compensate each-other. We consider the
general case: the voltages are below the gap, the system is either
dirty or clean. It is shown that I2(V1,0)=0 for general
configuration of the normal leads; if the first lead injects spin
polarized current then I2=0, but spin current in the lead-2 is
finite. XISIN structure, where X is a source of the spin polarized
current could be applied as a filter separating spin current from
charge current. We do an analytical progress calculating
I1(V1,V2), I2(V1,V2).
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