Tunneling conductance in a gapped graphene-based normal metal–insulator–d-wave superconductor junction: Case of massive Dirac electrons

Abstract

Using the extended Blonder–Tinkham–Klapwijk formalism, the normal conductance spectra in a normal/insulator/d-wave superconductor gapped graphene junction, considering effect of asymmetric pairing potential (anisotropic d-wave) is investigated in the limit of a thin barrier. The charged Dirac carriers in this structure are treated as massive relativistic particles. The exact solutions of Dirac–Bogoliubov–de Gennes Hamiltonain for three normal gapped graphene, insulator and superconductor region of junction and related normal and Andreev reflection coefficients are obtained. In this work, we focus to study in detail the effect of rotated angle α caused by d-wave order parameter of superconductor in tunneling conductance behavior in our system. In particular, the conductance spectra in terms of the bias voltage eV, the d-wave superconducting orientation angular α and also the electrostatic potentials U 0 and V 0 is plotted. It is shown that by increasing rotated angle α in that case of U 0 → ∞ and mv 2 F / E F =0.99, the maximum of resonant peak of normal conductance decreases and also the position of peak shifts from eV / Δ = 1 to progressively lower values. We also observe an oscillatory behavior of conductance versus insulator potential V 0.