Nonlocal Andreev reflection at high transmissions

Kalenkov, Mikhail S.; Zaikin, Andrei D.

doi:10.1103/physrevb.75.172503

Cited by 69 publications

(107 citation statements)

References 24 publications

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“…Cooper pairs in superconducting nanostructures provide a potential source of entangled electrons [1,2,3,4,5], a possibility that has been recently explored in conventional superconductors both theoretically [6,7,8,9,10,11,12,13,14,15,16] and experimentally [17,18,19,20]. In a typical experimental device, a superconducting region is contacted by several metallic electrodes at nanoscale distances with the aim of analyzing the non-local transport properties at subgap voltages.…”

Section: Introductionmentioning

confidence: 99%

Long-range crossed Andreev reflections in high-temperature superconductors

2009

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We analyze the non-local transport properties of a d-wave superconductor coupled to metallic electrodes at nanoscale distances. We show that the non-local conductance exhibits an algebraical decay with distance rather than the exponential behavior which is found in conventional superconductors. Crossed Andreev processes, associated with electronic entanglement, are favored for certain orientations of the symmetry axes of the superconductor with respect to the leads. These properties would allow its experimental detection using present technologies.

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Section: Introductionmentioning

confidence: 99%

Long-range crossed Andreev reflections in high-temperature superconductors

2009

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“…This noncollinearity is particularly important for nonlocal transport processes where the wire length is typically comparable to the superconducting coherence length [10][11][12][13][14][15][16][17][18][19]. In general, when an electron is injected from one N lead to the S, it can either form a Cooper pair in the S and leave an out-going hole in the other N lead; or it can propagate through the S to the other lead.…”

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confidence: 99%

“…In general, when an electron is injected from one N lead to the S, it can either form a Cooper pair in the S and leave an out-going hole in the other N lead; or it can propagate through the S to the other lead. These two different processes respectively correspond to the cross Andreev reflection (CAR) [10,11] and the direct charge transfer [13], which can be differentiated and respectively blocked in a noncollinear nonlocal transport. A paradigm scenario here is by placing two HM leads in contact with the wire (see Fig.…”

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confidence: 99%

Noncollinear Andreev reflections in semiconductor nanowires

Cao

et al. 2014

Phys. Rev. B

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We show that noncollinear Andreev reflections can be induced at interfaces of semiconductor nanowires with spin-orbit coupling, Zeeman splitting and proximity-induced superconductivity. In a noncollinear local Andreev reflection, the spin polarizations of the injected and the retro-reflected carriers are typically at an angle which is tunable via system parameters. While in a nonlocal transport, this noncollinearity enables us to identify and block, at different voltage configurations, the noncollinear cross Andreev reflection and the direct charge transfer processes. We demonstrate that the intriguing noncollinearity originates from the spin-dependent coupling between carriers in the lead and the lowest discrete states in the wire, which, for a topological superconducting nanowire, are related to the overlap-induced hybridization of Majorana edge states in a finite system. These interesting phenomena can be observed in semiconductor nanowires of experimentally relevant lengths, and are potentially useful for spintronics.

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“…Elastic cotunneling (EC) is to lowest order in tunneling amplitude equal in magnitude and opposite in sign to CAR, resulting in a vanishing nonlocal conductance [8]. Including higher order terms, which become important in more transparent junctions, unfortunately provides EC to be the dominant process [9].Several proposals have been put forward to enhance the CAR current. Using ferromagnetic half-metals (F) as leads can result in dominant CAR in an antiparallel magnetization alignment [3], though spin entanglement is then questionable.…”

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confidence: 99%

mentioning

confidence: 99%

Chemically mediated diffusion of d-metals and B through Si and agglomeration at Si-on-Mo interfaces

Tsarfati

Zoethout

Kruijs

et al. 2009

Journal of Applied Physics

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Perfect Cooper pair splitting is proposed, based on crossed Andreev reflection (CAR) in a p-type semiconductor-superconductor-n-type semiconductor (pSn) junction. The ideal splitting is caused by the energy filtering that is enforced by the band structure of the electrodes. The pSn junction is modeled by the Bogoliubov-de Gennes equations and an extension of the Blonder-Tinkham-Klapwijk theory beyond the Andreev approximation. Despite a large momentum mismatch, the CAR current is predicted to be large. The proposed straightforward experimental design and the 100% degree of pureness of the nonlocal current open the way to pSn structures as high quality sources of entanglement. Spatially separated entangled electron pairs arise in hybrid normal-metal-superconductor structures. Andreev reflection (AR) is the conversion of an electron into a hole at the interface between a normal-metal or semiconductor and a superconductor [1]. This makes CAR a promising source of locally separated entangled electrons as building block for solid state Bell-inequality experiments, quantum computation and quantum teleportation [4,5].The Bell inequality can only be violated when the CAR fraction is larger than 1= ffiffiffi 2 p of the total current [6]. Despite the intensive investigation, the CAR fraction is usually small due to competing processes [7]. Aside from local AR, tunneling of a particle from one lead to another can occur. Elastic cotunneling (EC) is to lowest order in tunneling amplitude equal in magnitude and opposite in sign to CAR, resulting in a vanishing nonlocal conductance [8]. Including higher order terms, which become important in more transparent junctions, unfortunately provides EC to be the dominant process [9].Several proposals have been put forward to enhance the CAR current. Using ferromagnetic half-metals (F) as leads can result in dominant CAR in an antiparallel magnetization alignment [3], though spin entanglement is then questionable. Pure nonlocal Cooper pair splitting is predicted in a superconductor-topological insulator structure [10], but the fabrication will be challenging. Both the electromagnetic environment [11] and a change in the density of states (DOS) of a superconductor due to an ac bias [12] can result in dominant CAR, though the influences are expected to be small. A larger effect is predicted by Cayssol [13] in an n-type graphene superconductor-p-type graphene junction. However, full cancellation of EC and AR is only at precise biasing to the Dirac point and at a small range of the energy spectrum so that the current is not completely carried by CAR. Optimization of CAR may also be realized by using the Coulomb interaction [4]. Recent experiments indicated great potential of using the energy to discriminate CAR [15], although the splitting efficiency is yet small.Here, we propose a strategy for ideal 100% nonlocal Cooper pair splitting, with no contributions from AR and EC, in a relatively straightforward device. Making use of the energy difference between the incoming electron and the And...

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Nonlocal Andreev reflection at high transmissions

Cited by 69 publications

References 24 publications

Long-range crossed Andreev reflections in high-temperature superconductors

Long-range crossed Andreev reflections in high-temperature superconductors

Noncollinear Andreev reflections in semiconductor nanowires

Chemically mediated diffusion of d-metals and B through Si and agglomeration at Si-on-Mo interfaces

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