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Journal of Current Science and Technology

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Rangsit Journal of Arts and Sciences. Vol.1 No.2 , July - December 2011.

Influence of pair breaking effects on the long-range odd triplet superconductivity in a ferromagnet/superconductor bilayer

Thanasit Rachataruangsit and Suthat Yoksan

Abstract

           The spin-dependent potential together with magnetic impurity and the spin-orbit scatterings were incorporated into the de Gennes-Takahashi-Tachiki theory of a diffusive superconductor-and-ferromagnetic metal to derive a formulation of the odd triplet superconductivity proximity effect.  It is found that when the spin exchange interaction is inhomogeneous, i.e., the Neel spiral magnetic order, a new type of triplet condensate is generated, due to the broken time-reversal invariance.  The triplet amplitude still contains the s-wave state, similar to the conventional singlet pairing, but the frequency symmetry must be odd to obey the Pauli's exclusion principle. As a result, the self-consistent order parameter contains only the singlet pair amplitude.  The superconducting critical temperature of the bilayer is obtained in the single mode approximation and takes the form of the Abrikosov-Gorkov formula.  The necessary condition for the occurrence of the induced long-range triplet component in the ferromagnet layer is characterized by the modulation of the pair amplitudes in the transverse direction.  The possibility of the cryptoferromagnetic state, corresponding to the finite value of the spiral wave vector, is demonstrated in favor of the superconductivity.  In addition, the influence of the magnetic impurity and the spin-orbit scattering is to decrease the decay length and to increase the oscillation period of the pair amplitudes which in turn enhances the critical temperature but in a less pronounced non-monotonicity manner.

Keywords: odd triplet superconductivity, ferromagnetism, proximity effect, transition temperature, impurity scattering, spin-orbit scattering

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DOI: 10.14456/rjas.2011.14