247 research outputs found
Ab initio Evidence for Strong Correlation Associated with Mott Proximity in Iron-based Superconductors
We predict that iron-based superconductors discovered near d6 configuration
(5 Fe 3d orbitals filled by 6 electrons) is located on the foot of an
unexpectedly large dome of correlated electron matter centered at the Mott
insulator at d5 (namely, half filling). This is based on the many-variable
variational Monte-Carlo results for ab initio low-energy models derived by the
downfolding. The d5 Mott proximity extends to subsequent emergence of
incoherent metals, orbital differentiations due to the Mott physics and
Hund's-rule coupling, followed by antiferromagnetic quantum criticality, in
quantitative accordance with available experiments.Comment: 9 pages, 5 figure
Ab initio derivation of electronic low-energy models for C60 and aromatic compounds
We present a systematic study for understanding the relation between
electronic correlation and superconductivity in C60 and aromatic compounds. We
derived, from first principles, extended Hubbard models for twelve compounds;
fcc K3C60, Rb3C60, Cs3C60 (with three different lattice constants), A15 Cs3C60
(with four different lattice constants), doped solid picene, coronene, and
phenanthrene. We show that these compounds are strongly correlated and have a
similar energy scale of the bandwidth and interaction parameters. However, they
have a different trend in the relation between the strength of electronic
correlation and superconducting transition temperature; while the C60 compounds
have a positive correlation, the aromatic compounds exhibit negative
correlation.Comment: 13 pages, 7 figures, 7 table
Ab initio two-dimensional multiband low-energy models of EtMe_3Sb[Pd(dmit)_2]_2 and \kappa-(BEDT-TTF)_2Cu(NCS)_2 with comparisons to single-band models
We present ab initio two-dimensional extended Hubbard-type multiband models
for EtMe_3Sb[Pd(dmit)_2]_2 and \kappa-(BEDT-TTF)_2Cu(NCS)_2, after a
downfolding scheme based on the constrained random phase approximation (cRPA)
and maximally-localized Wannier orbitals, together with the dimensional
downfolding. In the Pd(dmit)_2 salt, the antibonding state of the highest
occupied molecular orbital (HOMO) and the bonding/antibonding states of the
lowest unoccupied molecular orbital (LUMO) are considered as the orbital
degrees of freedom, while, in the \kappa-BEDT-TTF salt, the
HOMO-antibonding/bonding states are considered. Accordingly, a three-band model
for the Pd(dmit)_2 salt and a two-band model for the \kappa-(BEDT-TTF) salt are
derived. We derive single band models for the HOMO-antibonding state for both
of the compounds as well.Comment: 10 pages, 9 figures, 3 tables; submitted to Physical Review
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