78 research outputs found
Many-body effects in iron pnictides and chalcogenides -- non-local vs dynamic origin of effective masses
We apply the quasi-particle self-consistent GW (QSGW) approximation to some
of the iron pnictide and chalcogenide superconductors. We compute Fermi
surfaces and density of states, and find excellent agreement with experiment,
substantially improving over standard band-structure methods. Analyzing the
QSGW self-energy we discuss non-local and dynamic contributions to effective
masses. We present evidence that the two contributions are mostly separable,
since the quasi-particle weight is found to be essentially independent of
momentum. The main effect of non locality is captured by the static but
non-local QSGW effective potential. Moreover, these non-local self-energy
corrections, absent in e.g. dynamical mean field theory (DMFT), can be
relatively large. We show, on the other hand, that QSGW only partially accounts
for dynamic renormalizations at low energies. These findings suggest that QSGW
combined with DMFT will capture most of the many-body physics in the iron
pnictides and chalcogenides.Comment: 4+ pages, 3 figure
Strain-induced tuning of the electronic Coulomb interaction in 3d transition metal oxide perovskites
Epitaxial strain offers an effective route to tune the physical parameters in
transition metal oxides. So far, most studies have focused on the effects of
strain on the bandwidths and crystal field splitting, but recent experimental
and theoretical works have shown that also the effective Coulomb interaction
changes upon structural modifications. This effect is expected to be of
paramount importance in current material engineering studies based on
epitaxy-based material synthesization. Here, we perform constrained random
phase approximation calculations for prototypical oxides with a different
occupation of the d shell, LaTiO3 (d1), LaVO3 (d2), and LaCrO3 (d3), and
systematically study the evolution of the effective Coulomb interactions
(Hubbard U and Hund's J) when applying epitaxial strain. Surprisingly, we find
that the response upon strain is strongly dependent on the material. For
LaTiO3, the interaction parameters are determined by the degree of localization
of the orbitals, and grow with increasing tensile strain. In contrast, LaCrO3
shows the opposite trends: the interactions parameters shrink upon tensile
strain. This is caused by the enhanced screening due to the larger electron
filling. LaVO3 shows an intermediate behavior
Combined GW and dynamical mean field theory: Dynamical screening effects in transition metal oxides
We present the first dynamical implementation of the combined GW and
dynamical mean field scheme ("GW+DMFT") for first principles calculations of
the electronic properties of correlated materials. The application to the
ternary transition metal oxide SrVO3 demonstrates that this schemes inherits
the virtues of its two parent theories: a good description of the local low
energy correlation physics encoded in a renormalized quasi-particle band
structure, spectral weight transfer to Hubbard bands, and the physics of
screening driven by long-range Coulomb interactions. Our data is in good
agreement with available photoemission and inverse photoemission spectra; our
analysis leads to a reinterpretation of the commonly accepted "three-peak
structure" as originating from orbital effects rather than from the electron
addition peak within the t2g manifold.Comment: replaced with published version (6 pages, 3 figures); first version
was submitted to PRL on June 19, 201
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