Plane-wave many-body corrections to the conductance in bulk tunnel junctions
Résumé
The conductance of bulk metal-insulator-metal junctions is evaluated by the Landauer formula using an ab initio electronic structure calculated using a plane-wave basis set within density functional theory and beyond, i.e., including exact nonlocal exchange using hybrid functional (HSE) or many-body G 0 W 0 and Coulomb-hole screened exchange (COHSEX) quasiparticle 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 semilocal 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 wave functions rather than energies, and thus not directly related to the correction of the band gap of bulk MgO. G 0 W 0 and HSE both provide a 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.
Domaines
Physique [physics]
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