Tight-binding study of bilayer graphene Josephson junctions

Muñoz, W. A.; Covaci, Lucian; Peeters, F. M.

doi:10.1103/physrevb.86.184505

Cited by 14 publications

(15 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous self-consistent calculations performed by us revealed a similar sub-lattice polarization in the pair correlation function along a bilayer graphene JJ 19 . It can be observed in Fig.…”

supporting

confidence: 65%

Superconducting current and proximity effect in ABA and ABC multilayer graphene Josephson junctions

2013

Self Cite

View full text Add to dashboard Cite

Using a numerical tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method we describe Josephson junctions made of multilayer graphene contacted by top superconducting gates. Both Bernal (ABA) and rhombohedral (ABC) stacking are considered and we find that the type of stacking has a strong effect on the proximity effect and the supercurrent flow. For both cases the pair amplitude shows a polarization between dimer and non-dimer atoms, being more pronounced for rhombohedral stacking. Even though the proximity effect in non-dimer sites is enhanced when compared to single layer graphene, we find that the supercurrent is suppressed. The spatial distribution of the supercurrent shows that for Bernal stacking the current flows only in the top-most layers while for rhombohedral stacking the current flows throughout the whole structure. The exceptional characteristics of carriers in a single graphene layer gives rise to unusual properties of superconductor-graphene junctions such as specular Andreev reflection 1 and finite superconducting current at the neutrality point 2 . Although there is still no clear evidence of the novel electron-hole conversion, a bipolar proximity-induced supercurrent has been detected in superconducting-graphene-superconducting Josephson junctions (JJ)3-6 opening a new perspective for Josephson field transistors. In these devices, carrier density modulations by the gate voltage playes an important role in controlling the strength of the proximity effect and therefore the dissipationless current flowing through the junction. It is also expected that other graphene structures show interesting properties when in contact with superconducting leads. In fact, Josephson junctions with non-superconducting fewlayer graphite films have been the focus of experimental investigations [7][8][9][10] . In most of the few preceding theoretical studies 11-13 the proximity-induced superconducting correlations in multilayer graphene were determined using analytical approximations where the electronic description was limited to parabolic energy bands near the Fermi energy. As a consequence the depth dependence of the order parameter was neglected and in some cases the superconducting pair diffusion was reduced to a 2-dimensional scenario, therefore ignoring any spread of the Cooper pairs among the different layers. Since all the experimental setups require top superconducting contacts, a calculation taking into account the depth dependence of the pair correlation is needed.In this Rapid Communication we describe the 3-dimensional diffusion of Cooper pairs through a nonsuperconducting multilayer graphene junction connected to two top superconducting electrodes. The Josephson superconducting current is also studied by setting a phase gradient between the superconducting leads. We find significant differences between the two possible stacking orders, Bernal and rhombohedral. For junctions with Bernal stacking the supercurrent flows mostly through the two top-most layers while for junctions with rhomb...

show abstract

supporting

confidence: 65%

Superconducting current and proximity effect in ABA and ABC multilayer graphene Josephson junctions

2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…Placed in contact with superconductors, graphene manifests unconventional superconducting properties [178]. The authors of [179] experimentally studied the Josephson effect [180] in mesoscopic junctions consisting of a short sample of graphene monolayer placed between two closely spaced superconducting electrodes.…”

Section: Superconductivity In An Idealized Graphene Monolayermentioning

confidence: 99%

Anomalous superconductivity and superfluidity in repulsive fermion systems

2015

View full text Add to dashboard Cite

We discuss the mechanisms of unconventional superconductivity and superfluidity in 3D and 2D fermionic systems with purely repulsive interaction at low densities. We construct phase diagrams of these systems and find the areas of the superconducting state in free space, as well as on the lattice in the framework of the Fermi-gas model with hard-core repulsion, the Hubbard model, the Shubin-Vonsovsky model, and the t − J model. We demonstrate that the critical superconducting temperature can be greatly increased in the spin-polarized case or in a two-band situation already at low densities. The proposed theory is based on the Kohn-Luttinger mechanism or its generalizations and explains or predicts anomalous p-, d-, and f -wave pairing in various materials, such as high-temperature superconductors, the idealized monolayer and bilayer of doped graphene, heavy-fermion systems, layered organic superconductors, superfluid 3 He, spin-polarized 3 He mixtures in 4 He, ultracold quantum gases in magnetic traps, and optical lattices.

show abstract

“…The elements of the matrix (1) are calculated within the approximation of the Gor'kov Green's functions by implementing the Chebyshev-Bogoliubov-de Gennes method [11,30,34]:…”

Section: A the Chebyshev-bogoliubov-de Gennes Methodsmentioning

confidence: 99%

“…1. Following closely the recipe implemented in previous works [29,30], we model the influence of the right and left superconducting contacts by assuming an on-site attractive pairing potential U = −2.0t 0 and high doping, μ = 0.6t 0 , where t 0 = 2.7 eV. In this way, we introduce a s-wave superconducting state over the outermost regions in the graphene sheet separated by a distance L = 12.8 nm.…”

Section: Modelmentioning

confidence: 99%

Disordered graphene Josephson junctions

2015

Self Cite

View full text Add to dashboard Cite

A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method is used to describe disordered single-layer graphene Josephson junctions. Scattering by vacancies, ripples or charged impurities is included. We compute the Josephson current and investigate the nature of multiple Andreev reflections, which induce bound states appearing as peaks in the density of states for energies below the superconducting gap. In the presence of single atom vacancies, we observe a strong suppression of the supercurrent that is a consequence of strong inter-valley scattering. Although lattice deformations should not induce inter-valley scattering, we find that the supercurrent is still suppressed, which is due to the presence of pseudo-magnetic barriers. For charged impurities, we consider two cases depending on whether the average doping is zero, i.e. existence of electron-hole puddles, or finite. In both cases, short range impurities strongly affect the supercurrent, similar to the vacancies scenario

show abstract

Tight-binding study of bilayer graphene Josephson junctions

Cited by 14 publications

References 21 publications

Superconducting current and proximity effect in ABA and ABC multilayer graphene Josephson junctions

Superconducting current and proximity effect in ABA and ABC multilayer graphene Josephson junctions

Anomalous superconductivity and superfluidity in repulsive fermion systems

Disordered graphene Josephson junctions

Contact Info

Product

Resources

About