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Enhanced specular Andreev reflection in bilayer graphene

Soori, Abhiram and Sahu, Manas Ranjan and Das, Anindya and Mukerjee, Subroto (2018) Enhanced specular Andreev reflection in bilayer graphene. In: PHYSICAL REVIEW B, 98 (7).

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Official URL: https://dx.doi.org/10.1515/crelle-2015-0075


Andreev reflection in graphene is special since it can be of two types, retro or specular. Specular Andreev reflection (SAR) dominates when the position of the Fermi energy in graphene is comparable to or smaller than the superconducting gap. Bilayer graphene (BLG) is an ideal candidate to observe the crossover from retro to specular since the Fermi energy broadening near the Dirac point is much weaker compared to monolayer graphene. Recently, the observation of signatures of SAR in BLG have been reported experimentally by looking at the enhancement of conductance at finite bias near the Dirac point. However, the signatures were not very pronounced possibly due to the participation of normal quasiparticles at bias energies close to the superconducting gap. Here, we propose a scheme to observe the features of enhanced SAR even at zero bias at a normal metal (NM)-superconductor (SC) junction on BLG. Our scheme involves applying a Zeeman field to the NM side of the NM-SC junction on BLG (making the NM ferromagnetic), which energetically separates the Dirac points for up spin and down spin. We calculate the conductance as a function of chemical potential and bias within the superconducting gap and show that well-defined regions of specular- and retro-type Andreev reflection exist. We compare the results with and without superconductivity. We also investigate the possibility of the formation of a p-n junction at the interface between the NM and SC due to a work function mismatch.

Item Type: Journal Article
Additional Information: Copyright of this article belong to AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 16 Aug 2018 16:02
Last Modified: 16 Aug 2018 16:02
URI: http://eprints.iisc.ac.in/id/eprint/60441

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