Influence of spin filtering and spin mixing on the subgap structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>I</mml:mi><mml:mtext>−</mml:mtext><mml:mi>V</mml:mi></mml:mrow></mml:math>characteristics in a superconducting quantum point contact

Bobkova, I. V.; Bobkov, A. M.

doi:10.1103/physrevb.76.094517

Cited by 6 publications

(4 citation statements)

References 32 publications

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“…In particular, the transmission properties of spin-↑ and spin-↓ electrons into a ferromagnetic metal are different, which gives rise to both spin-dependent conductivities (spin filtering) 27 and spin-dependent phase shifts (spin-DIPS) at the interface. 14,17,[28][29][30][31][32][33][34][35][36] A generalization of boundary conditions to spin-active interfaces was given in Refs. [35][36][37], that has been generalized to include systems with strong exchange splitting of the energy bands in Refs.…”

Section: Introductionmentioning

confidence: 99%

Signature of odd-frequency pairing correlations induced by a magnetic interface

et al. 2010

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We investigate the mutual proximity effect in a normal metal contacted to a superconductor through a magnetic interface. Analytical and self-consistent numerical results are presented, and we consider both the diffusive and ballistic regimes. We focus on the density of states in both the normal and superconducting region, and find that the presence of spin-dependent phase-shifts occurring at the interface qualitatively modifies the density of states. In particular, we find that the proximity-induced pairing amplitudes in the normal metal region undergo a conversion at the Fermi level from pure even-frequency to odd-frequency. Above a critical value of the interface spin-polarization (or, equivalently, for fixed interface spin-polarization, above a critical interface resistance), only odd frequency correlations remain. This is accompanied by the replacement of the familiar proximity minigap or pseudogap in the normal layer by an enhancement of the density of states above its normal state value for energies near the chemical potential. The robustness of this effect towards inelastic scattering, impurity scattering, and the depletion of the superconducting order parameter close to the interface is investigated. We also study the inverse proximity effect in the diffusive limit. We find that the above-mentioned conversion persists also for thin superconducting layers comparable in size to the superconducting coherence length ξS, as long as the inverse proximity effect is relatively weak. Concomitantly, we find a shift in the critical interface resistance where the pairing conversion occurs. Our findings suggest a robust and simple method for producing purely odd-frequency superconducting correlations, that can be tested experimentally.

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Section: Introductionmentioning

confidence: 99%

Signature of odd-frequency pairing correlations induced by a magnetic interface

et al. 2010

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“…53 The latter is called the spin-mixing effect and it has been shown to be of crucial importance for the creation of exotic pairing correlations. 3,19,[53][54][55][56][57] So far, estimates of the magnitude of this effect and its dependence on physical parameters including not only the structure of the interface but also the Fermi surface geometry of the adjacent materials and the FM exchange splitting are still lacking. Instead, phenomenological models have been adopted that introduce a free parameter to account for it.…”

Section: Introductionmentioning

confidence: 99%

Theory of superconductor-ferromagnet point-contact spectra: The case of strong spin polarization

et al. 2010

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We study the impact of spin-active scattering on Andreev spectra of point contacts between superconductors(SCs) and strongly spin-polarized ferromagnets(FMs) using recently derived boundary conditions for the Quasiclassical Theory of Superconductivity. We describe the interface region by a microscopic model for the interface scattering matrix. Our model includes both spin-filtering and spin-mixing and is non-perturbative in both transmission and spin polarization. We emphasize the importance of spin-mixing caused by interface scattering, which has been shown to be crucial for the creation of exotic pairing correlations in such structures. We provide estimates for the possible magnitude of this effect in different scenarios and discuss its dependence on various physical parameters. Our main finding is that the shape of the interface potential has a tremendous impact on the magnitude of the spin-mixing effect. Thus, all previous calculations, being based on delta-function or box-shaped interface potentials, underestimate this effect gravely. As a consequence, we find that with realistic interface potentials the spin-mixing effect can easily be large enough to cause spin-polarized sub-gap Andreev bound states in SC/sFM point contacts. In addition, we show that our theory generalizes earlier models based on the Blonder-Tinkham-Klapwijk approach.

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“…Our idea relies on the possibility of fabricating spin-active interfaces. [9][10][11][12][13][14][15][16][17][18][19][20] One can imagine such interface as a magnetic layer with spin-dependent transmission amplitude and phase (via Larmor precession around the intrinsic magnetic moment of the layer). A superconductor coated with a spin-active layer hosts a pair of interface bound Andreev states, whose properties are controlled by parameters of the interface.…”

Section: Introductionmentioning

confidence: 99%

Spin imbalance in hybrid superconducting structures with spin-active interfaces

Shevtsov

Löfwander

2014

Phys. Rev. B

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We consider a heterostructure consisting of a normal metal and a superconductor separated by a spin-active interface. At finite bias voltages, spin-filtering and spin-mixing effects at the interface allow for an induced magnetization (spin imbalance) on the superconducting side of the junction, which relaxes to zero in the bulk. Such interfaces are also known to host a pair of in-gap Andreev bound states which were recently observed experimentally. We show that these states are responsible for the dominant contribution to the induced spin imbalance close to the interface. Motivated by recent experiments on spin-charge density separation in superconducting aluminum wires, we propose an alternative way to observe spin imbalance without applying an external magnetic field. We also suggest that the peculiar dependence of the spin imbalance on the applied bias voltage permits an indirect bound state spectroscopy.

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Influence of spin filtering and spin mixing on the subgap structure ofI−Vcharacteristics in a superconducting quantum point contact

Cited by 6 publications

References 32 publications

Signature of odd-frequency pairing correlations induced by a magnetic interface

Signature of odd-frequency pairing correlations induced by a magnetic interface

Theory of superconductor-ferromagnet point-contact spectra: The case of strong spin polarization

Spin imbalance in hybrid superconducting structures with spin-active interfaces

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