Amplification of Cooper pair splitting current in a graphene based Cooper pair beam splitter geometry

摘要

Motivated by the recent experiments [Scientific reports 6, 23051 (2016),Phys. Rev. Lett. 114, 096602 (2015)], we theoretically investigate Cooper pairsplitting current in a graphene based Cooper pair beam splitter geometry. Byconsidering the graphene based superconductor as an entangler device, insteadof normal (2D) BCS superconductor, we show that the Cooper pair splittingcurrent mediated by Crossed Andreev process is amplified compared to its normalsuperconductor counterpart. This amplification is attributed to the strongsuppression of local normal Andreev reflection process (arising from the Cooperpair splitting) from the graphene based superconductor to lead via the samequantum dot, in comparison to the usual 2D superconductor. Due to the vanishingdensity of states at the Dirac point of undoped graphene, a doped graphenebased superconductor is considered here and it is observed that Cooper pairsplitting current is very insensitive to the doping level in comparison to theusual 2D superconductor. The transport process of non-local spin entangledelectrons also depends on the type of pairing i.e. whether the electron-holepairing is on-site, inter-sublattice or the combination of both. Theinter-sublattice pairing of graphene causes the maximum non-local Cooper pairsplitting current, whereas presence of both pairing reduces the Cooper pairsplitting current.