Current-induced phase textures and pairbreaking in artificial ...

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15 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Current
-
induced phase textures and pairbreaking in artificial multilayeres and two
-
gap
superconductors
.


A. Gurevich
1

and V.M. Vinokur
2

1
University of Wisconsin, Madison, WI.

2
Argonne National Laboratory, Argonne, IL.



We discuss a new inhomogeneous state

in current
-
carrying superconducting multil
ayers or
superconductors with
multicomponent order parameter
s
.

Using the GL theory, we first show that
the current I flowing along a weakly coupled bilayer (with two different superconducting layers)
can result in

a two
-
stage pairbreaking process: 1. Current
-
induced interlayer decoupling, which
manifests itself in a transition from the phase
-
locked state at I < I
b

to a periodic chain of interlayer
2


phase slips for I > I
b
. Such phase texture re
-
distributes current
s between the layers, the period
of the texture L(I) decreases as I increases similar to the period of the vortex lattice L(H) in a long
Josephson junction. 2. The global pairbreaking at the depairing current I
d

>> I
u
. Next, we
consider current
-
induced pa
irbreaking in two
-
gap superconductors with two weakly coupled s
-
wave order parameters, as characteristic of MgB
2
. Using the Usadel equations we derive an
equation for the interband phase difference valid for all temperatures. This equation predicts the
beh
avior similar to that of a bilayer: At small currents, I < I
b

the


and


bands are phase
-
locked,
while for I > I
b
, the band decoupling transition occurs as a static interband phase slip structure
forms along the direction of current flow. Such interband
textures appear in an equilibrium
current
-
carrying state below the depairing limit, I
b
<< I
d
, similar to the phase textures caused by
nonequilibrium charge imbalance [1].




1. A. Gurevich and V.M. Vinokur, Phys. Rev. Lett.
90
, 047004 (2003).