The possibility of measuring intrinsic electronic correlations in graphene using a d-wave contact Josephson junction

TL;DR

This paper proposes using d-wave contact graphene Josephson junctions to measure intrinsic electronic correlations, specifically spin-singlet bonds, which are theorized to be significant in graphene but lack quantitative estimates.

Contribution

It introduces a theoretical framework showing how intrinsic spin-singlet bond correlations in graphene can be enhanced and detected via Josephson junctions, providing a new experimental approach.

Findings

SB correlations are strongly enhanced in d-wave contact graphene Josephson junctions.

The superconducting decay length follows a 1/(T-T_c) dependence.

Proposes experimental measurement of intrinsic SB correlations in graphene.

Abstract

While not widely recognized, electronic correlations might play an important role in graphene. Indeed, Pauling's resonance valence bond (RVB) theory for the pp-bonded planar organic molecules, of which graphene is the infinite extension, already established the importance of the nearest neighbor spin-singlet bond (SB) state in these materials. However, despite the recent growth of interest in graphene, there is still no quantitative estimate of the effects of Coulomb repulsion in either undoped or doped graphene. Here we use a tight-binding Bogoliubov-de Gennes (TB BdG) formalism to show that in unconventional d-wave contact graphene Josephson junctions the intrinsic SB correlations are strongly enhanced. We show on a striking effect of the SB correlations in both proximity effect and Josephson current as well as establishing a 1/(T-T_c) functional dependence for the superconducting decay length. Here T_c is the superconducting transition temperature for the intrinsic SB correlations, which depends on both the effects of Coulomb repulsion and the doping level. We therefore propose that d-wave contact graphene Josephson junctions will provide a promising experimental system for the measurement of the effective strength of intrinsic SB correlations in graphene.