Year: 2025
Type: article
Abstract: In this work, we consider superconductor/flat band material/superconductor (S/FB/S) Josephs on junctions (JJs) where the flat band material possesses isolated flat bands with exactly zero Fermi velocity. Contrary to conventional S/N/S JJs where the critical Josephson current vanishes when the Fermi velocity goes to zero, we show in this work that the critical current in the S/FB/S junction is controlled by the quantum metric length ξ QM of the flat bands. Microscopically, when ξ QM of the flat band is long enough, the interface bound states originally localized at the two S/FB, FB/S interfaces can penetrate deeply into the flat band material and hybridize to form Andreev bound states (ABSs). These ABSs are able to carry long range and sizable supercurrents. Importantly, ξ QM also controls how far the proximity effect can penetrate into the flat band material. This stands in sharp contrast to the de Gennes' theory for S/N junctions which predicts that the proximity effect is expected to be zero when the Fermi velocity of the normal metal is zero. We further suggest that the S/FB/S junctions would give rise to a new type of resonant Josephson transistor which can carry a sizable and highly gate-tunable supercurrent.
Source: Physical Review Research
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,625
Awards: G1106148883, G1281633919, G1676763655, Josephson diode effect and other novel superconducting phenomena in two-dimensional superconductors, Magnetoelectric effects of graphene and transition metal dichalcogenides based Moire superlattices, Superconductivity and Nonlinear Hall Effects in Transition Metal Dichalcogenides, G4315702481, G434337789, G487931150, The study of superconductor/correlated insulator junctions in moire materials, G741456967, G8646101894
OpenAlex ID: W4411370529