810 research outputs found
Wannier Function Approach to Realistic Coulomb Interactions in Layered Materials and Heterostructures
We introduce an approach to derive realistic Coulomb interaction terms in
free standing layered materials and vertical heterostructures from ab-initio
modelling of the corresponding bulk materials. To this end, we establish a
combination of calculations within the framework of the constrained random
phase approximation, Wannier function representation of Coulomb matrix elements
within some low energy Hilbert space and continuum medium electrostatics, which
we call Wannier function continuum electrostatics (WFCE). For monolayer and
bilayer graphene we reproduce full ab-initio calculations of the Coulomb matrix
elements within an accuracy of eV or better. We show that realistic
Coulomb interactions in bilayer graphene can be manipulated on the eV scale by
different dielectric and metallic environments. A comparison to electronic
phase diagrams derived in [M. M. Scherer et al., Phys. Rev. B 85, 235408
(2012)] suggests that the electronic ground state of bilayer graphene is a
layered antiferromagnet and remains surprisingly unaffected by these strong
changes in the Coulomb interaction.Comment: 12 pages, 8 figure
Bandwidth renormalization due to the intersite Coulomb interaction
The theory of correlated electrons is currently moving beyond the
paradigmatic Hubbard , towards the investigation of intersite Coulomb
interactions. Recent investigations have revealed that these interactions are
relevant for the quantitative description of realistic materials. Physically,
intersite interactions are responsible for two rather different effects:
screening and bandwidth renormalization. We use a variational principle to
disentangle the roles of these two processes and study how appropriate the
recently proposed Fock treatment of intersite interactions is in correlated
systems. The magnitude of this effect in graphene is calculated based on cRPA
values of the intersite interaction. We also observe that the most interesting
charge fluctuation phenomena actually occur at elevated temperatures,
substantially higher than studied in previous investigations.Comment: New appendix on benzen
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