2006/09/25 by M. Titov, A. Ossipov, Alexander Ossipov +1 · 5 citations
Materials Science · Physics and Astronomy · #Andreev reflection #Band gap #Condensed matter physics #Density of states #Electron #Excitation #Fermi energy #Graphene #Graphene research and applications #Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Quantum mechanics #Superconductivity #cond-mat.mes-hall
paper · pdf · doi:10.1103/physrevb.75.045417
published as Phys.Rev.B 75, 045417 (2007) · 8 pages, 10 figures
arxiv created 2006/09/25 · openalex publication_date 2007/01/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We calculate the density of states of electron-hole excitations in a superconductor--normal-metal--superconductor (SNS) junction in graphene, in the long-junction regime that the superconducting gap \ensuremathΔ0 is much larger than the Thouless energy ET=\ensuremathℏv∕d (with v the carrier velocity in graphene and d the separation of the NS boundaries). If the normal region is undoped, the excitation spectrum consists of neutral modes that propagate along the boundaries---transporting energy but no charge. These ``Andreev modes'' are a coherent superposition of electron states from the conduction band and hole states from the valence band, coupled by specular Andreev reflection at the superconductor. The lowest Andreev mode has an excitation gap of E0=(1)/(2)(\ensuremathπ\ensuremath-\ensuremath|\ensuremathφ\ensuremath|)ET, with \ensuremathφ∊(\ensuremath-\ensuremathπ,\ensuremathπ) the superconducting phase difference. At high doping (Fermi energy \ensuremathμ⪢ET) the excitation gap vanishes \ensuremath∝E0(ET∕\ensuremathμ)2, and the usual gapless density of states of Andreev levels is recovered. We use our results to calculate the \ensuremathφ dependence of the thermal conductance of the graphene channel.