Detecting entangled states in graphene via crossed Andreev reflection

Benjamin, Colin; Pachos, Jiannis K.

doi:10.1103/physrevb.78.235403

Cited by 56 publications

(34 citation statements)

References 22 publications

(18 reference statements)

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“…Besides nearly ballistic conductance with huge mean free paths, spin-orbit coupling in graphene is expected to be weak, which implies long spin coherence times. According to theory, production of entangled electrons by CPS works well in graphene [13,14]. Because of the unique properties of graphene, it is also possible that a Majorana fermion, a fermion which is its own antiparticle, would be stabilized in the superconductor-graphene junction [15,16].…”

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confidence: 99%

Cooper Pair Splitting by Means of Graphene Quantum Dots

et al. 2015

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Split Cooper pair is a natural source for entangled electrons which is a basic ingredient for quantum information in solid state. We report an experiment on a superconductor-graphene double quantum dot (QD) system, in which we observe Cooper pair splitting (CPS) up to a CPS efficiency of ∼ 10%. With bias on both QDs, we are able to detect a positive conductance correlation across the two distinctly decoupled QDs. Furthermore, with bias only on one QD, CPS and elastic co-tunneling can be distinguished by tuning the energy levels of the QDs to be asymmetric or symmetric with respect to the Fermi level in the superconductor.

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confidence: 99%

Cooper Pair Splitting by Means of Graphene Quantum Dots

et al. 2015

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“…However, the CAR process could be often completely masked by a competing process known as elastic cotunneling (EC) that occurs in the same hybrid S junction, and these two processes have the same transmission coefficients in terms of the lowest-order perturbation approximation, 9 thus necessitating the usage of noise measurement to find fingerprints of the CAR process. [10][11][12][13] Recently, several proposals [14][15][16][17][18][19] were put forward to find an exclusive CAR by suppressing both the EC and local AR processes. Veldhorst et al 16 have predicted that a 100% fraction of the CAR is possible in a n-type semiconductor/S/p-type semiconductor hybrid junction by making use of the band structure imposed energy filtering; however, the optimal operation requires that the Fermi level is fixed at the bottom of the left conduction band and the vertex of the right valence band, E c = E v .…”

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confidence: 99%

Crossed Andreev reflection in a zigzag graphene nanoribbon-superconductor junction

Wang

Liu

2012

Phys. Rev. B

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We investigate the crossed Andreev reflection (CAR) in a zigzag graphene nanoribbon/superconductor/nanoribbon junction. It is shown that when the zigzag chain number of the ribbon is even and only the zero-energy mode is involved in transport, either the elastic cotunneling or the local Andreev reflection could be entirely suppressed by using a gate voltage whereas a sizeable CAR is achieved. When one of the ribbon leads is magnetized, not only the CAR is exclusive but also the spin state of the CAR transmission is nonlocally controllable. The physical origin is the peculiar valley selection rule in the even zigzag graphene nanoribbon. The ideal Cooper-pair splitting in the proposed device holds for all applied bias in the superconducting energy gap.

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“…6, is in sharp contrast to the conventional superconductor junction where G CAR always exhibits an exponential decay behavior as a function of l/ξ [36]. On the other hand, compared to the graphene case (the G CAR current is maximum around ξ ) [37], the novel aspect of the present junction is the resonant peaks maximum central around ξ/2. The novel behavior of G CAR may be understood as follows.…”

Section: B Numerical Results and Discussionmentioning

confidence: 58%

Pure valley- and spin-entangled states in aMoS2-based bipolar transistor

et al. 2014

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In this study, we show that the local Andreev reflection not only can be tuned largely by the type of the normal metal electrode, it also is related to the electrostatic potential in the superconductor region in a MoS 2 -based n(p)-type metal/superconductor junction. In a MoS 2 -based n-type metal/n(p)-type superconductor/p-type metal (nSp) transistor, nonlocal pure valley-and spin-entangled current can be tuned by the length and local gate voltage of a superconductor region. In particular, switching the quasiparticle type in both structures results in a series of intriguing features. Such an effect is not attainable in a graphene-based junction where the electron-hole symmetry enables the symmetry results to be observed. Besides, we have shown that the crossed Andreev reflection exhibits a maximum around ξ/2 instead of the exponential decay behavior in conventional superconductors and a maximum around ξ in the graphene material. The proposed straightforward experimental design and pure valley-and spin-entangled state can pave the way for a wider use in the entanglement based on material group-VI dichalcogenides.

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Detecting entangled states in graphene via crossed Andreev reflection

Cited by 56 publications

References 22 publications

Cooper Pair Splitting by Means of Graphene Quantum Dots

Cooper Pair Splitting by Means of Graphene Quantum Dots

Crossed Andreev reflection in a zigzag graphene nanoribbon-superconductor junction

Pure valley- and spin-entangled states in aMoS2-based bipolar transistor

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