scholarly journals Andreev bound states at spin-active interfaces

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150002
Author(s):  
D. Beckmann ◽  
F. Hübler ◽  
M. J. Wolf ◽  
H. v. Löhneysen
Keyword(s):  
Bound States ◽  
Hybrid Structures ◽  
Cooper Pairs ◽  
Important Ingredient ◽  
Theme Issue ◽  
Andreev Bound States ◽  
Interface Scattering ◽  
Spin Dependent Scattering ◽  
Parameter Symmetry ◽  
Order Parameter Symmetry

Andreev bound states are ubiquitous in superconducting hybrid structures. They are formed near impurities, in Josephson junctions, in vortex cores and at interfaces. At spin-active superconductor–ferromagnet interfaces, Andreev bound states are formed due to spin-dependent scattering phases. Spin-dependent phase shifts are an important ingredient for the generation of triplet Cooper pairs in superconductor–ferromagnet hybrid structures. Spectroscopy of Andreev bound states is a powerful probe of superconducting order parameter symmetry, as well as spin-dependent interface scattering and the triplet proximity effect. This article is part of the theme issue ‘Andreev bound states’.

scholarly journals Theory of Andreev bound states in S-F-S junctions and S-F proximity devices

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150149 ◽  
Author(s):  
M. Eschrig
Keyword(s):  
Quantum Coherence ◽  
General Framework ◽  
Bound States ◽  
Hybrid Structures ◽  
Theme Issue ◽  
Josephson Devices ◽  
Andreev Bound States ◽  
Non Local ◽  
Metallic Parts ◽  
Strong Spin

Andreev bound states are an expression of quantum coherence between particles and holes in hybrid structures composed of superconducting and non-superconducting metallic parts. Their spectrum carries important information on the nature of the pairing, and determines the current in Josephson devices. Here, I focus on Andreev bound states in systems involving superconductors and ferromagnets with strong spin-polarization. I provide a general framework for non-local Andreev phenomena in such structures in terms of coherence functions, and show how the latter link wave function and Green-function based theories. This article is part of the theme issue ‘Andreev bound states’.

scholarly journals Andreev bound states in superconducting films and confined superfluid 3 He

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150144 ◽  
Author(s):  
Anton B. Vorontsov
Keyword(s):  
Bound States ◽  
Surface States ◽  
Surface Region ◽  
Theme Issue ◽  
Confined Geometry ◽  
Andreev Bound States ◽  
Broken Symmetries ◽  
Parent State ◽  
Open Questions ◽  
Coherence Lengths

This paper reviews confinement-driven phase transitions in superconductors and Bardeen–Cooper–Schrieffer superfluids, and the appearance in thin films of new phases that break the time-reversal or translational symmetry. The origins of the new phases are closely tied to the Andreev scattering processes involving particle-hole conversions that create surface quasiparticle states with energies inside the superconducting gap. Restructuring of the low-energy spectrum in the surface region of several coherence lengths ξ 0 results in large spatial variations of the superconducting order parameter. In confined geometry, such as slabs, films, pores or nano-dots, with one or more physical dimensions D ∼10 ξ 0 , the Andreev bound states can dominate properties of a superconductor, leading to modified experimental signatures. They can significantly change the energy landscape, and drive transitions into new superconducting phases. The new phases are expected in a variety of materials, from singlet d -wave superconductors to multi-component triplet superfluid 3 He, but properties of the new phases will depend on the symmetry of the parent state. I will highlight the connection between the Andreev surface states and confinement-stabilized phases with additional broken symmetries, describe recent progress and open questions in the theoretical and experimental investigation of superfluids in confined geometry. This article is part of the theme issue ‘Andreev bound states’.

scholarly journals Andreev reflection spectroscopy in transition metal oxides

2018 ◽  
Vol 376 (2125) ◽  
pp. 20150001
Author(s):  
Karen A. Yates ◽  
Lesley F. Cohen
Keyword(s):  
Transition Metal ◽  
Transition Metal Oxides ◽  
Bound States ◽  
Andreev Reflection ◽  
Transport Current ◽  
Reflection Spectroscopy ◽  
Theme Issue ◽  
Andreev Bound States ◽  
Current Spin Polarization

Here we review the literature concerning measurement of the Andreev reflection between a superconductor (S) and ferromagnet (F), with particular attention to the case where the ferromagnet is a transition metal oxide. We discuss the practicality of utilization of the current models for determination of the transport current spin polarization and examine the evidence for Andreev bound states. This article is part of the theme issue ‘Andreev bound states’.

scholarly journals Andreev bound states in ferromagnet-superconductor nanostructures

2003 ◽  
Vol 387 (1-2) ◽  
pp. 7-12 ◽  
Author(s):  
M. Krawiec ◽  
B.L. Györffy ◽  
J.F. Annett
Keyword(s):  
Bound States ◽  
Andreev Bound States

Example of how an unconventional order parameter symmetry may open new perspectives in the design of HTS Josephson junctions

2002 ◽  
Author(s):  
Francesco Tafuri ◽  
Filomena Lombardi ◽  
F. M. Granozio ◽  
F. Carillo ◽  
Fabrizio Riccia ◽  
...  
Keyword(s):  
Josephson Junctions ◽  
Order Parameter ◽  
Parameter Symmetry ◽  
Order Parameter Symmetry
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