Plane-wave many-body corrections to the conductance in bulk tunnel junctions

Abstract

The conductance of bulk metal-insulator-metal junctions is evaluated by the Landauer formula using an ab initio electronic structure calculated using a plane-waves basis set within density-functional theory (DFT) and beyond, i.e. including exact non-local exchange using hybrid functional (HSE) or many-body G0W0 and COHSEX quasiparticle (QP) schemes. We consider an Ag/MgO/Ag heterostructure model and we focus on the evolution of the zero-bias conductance as a function of the MgO film thickness. Our study shows that the correction of the electronic structure beyond semi-local density functionals goes in the right direction to improve the agreement with experiments, significantly reducing the zero-bias conductance. This effect becomes more evident at larger MgO thickness, that is in increasing tunneling regime. We also observe that the reduction of the conductance seems more related to the correction of wavefunctions rather than energies, and thus not directly related to the correction of the band-gap of bulk MgO. G0W0 and HSE both provide a correct band-gap in agreement with experiments, but only HSE gives a significant reduction of the conductance. COHSEX, while overestimating the band-gap, gives a reduction of the conductance very close to HSE. arXiv:1910.02761v1 [cond-mat.mes-hall]

Electronic and Thermal Properties of $\text{GeTe/Sb}_{2}\text{Te}_{3}$ Superlattices by ab-initio Approach: Impact of Van der Waals Gaps on Vertical Lattice Thermal Conductivity

“…Electronic structures are obtained using hybrid functional (HSE06) 20 with 12 × 12 × 4 Monkhorst-Pack(MP) mesh and 400 eV cut off energy. Electron transport in the vertical direction (perpendicular to VdW gap) is computed using the non-equilibrium Green's function (NEGF) formalism based on Wannier functions approach starting from HSE calculations 21 . The bias voltage is applied across the two electrodes, which are made of the same material.…”