456 research outputs found
Topological Quantum Phase Transition in 5 Transition Metal Oxide NaIrO
We predict a quantum phase transition from normal to topological insulators
in the 5 transition metal oxide NaIrO, where the transition can be
driven by the change of the long-range hopping and trigonal crystal field
terms. From the first-principles-derived tight-binding Hamiltonian we determine
the phase boundary through the parity analysis. In addition, our
first-principles calculations for NaIrO model structures show that the
interlayer distance can be an important parameter for the existence of a
three-dimensional strong topological insulator phase. NaIrO is
suggested to be a candidate material which can have both a nontrivial topology
of bands and strong electron correlations
Interplay between spin-orbit coupling and van Hove singularity in the Hund's metallicity of SrRuO
We investigate the dynamical properties of SrRuO at zero and very low
temperature using density functional theory plus dynamical mean-field theory
with an exact diagonalization solver. By considering rotationally invariant
local interaction, we examine how Hund's coupling and spin-orbit coupling
affect the correlated nature of the system. In the absence of Hund's coupling,
the system shows a Fermi liquid behavior over the entire range of temperatures
we consider. We confirm that the Fermi liquid persists at zero temperature even
with nonzero Hund's coupling; however, at sufficient temperatures Hund's
coupling significantly reduces the Fermi liquid regime and the system evolves
into a typical Hund's metal. At the bare electronic occupancy of SrRuO
(), a stronger Hund's metallicity accompanies a larger long-time
correlator. Remarkably, electron doping further destabilizes the Fermi liquid
even though the long-time correlator and magnetic fluctuations decrease upon
doping. This suppression of the Fermi liquid is driven by the van Hove
singularity above the Fermi level in SrRuO, combined with an enhanced
Van Vleck susceptibility by spin-orbit coupling. Such findings point to the
important role that electronic structure plays in the behavior of Hund's
metals, in addition to magnetic fluctuations.Comment: 7 pages, 4 figure
Fundamental thickness limit of itinerant ferromagnetic SrRuO thin films
We report on a fundamental thickness limit of the itinerant ferromagnetic
oxide SrRuO that might arise from the orbital-selective quantum confinement
effects. Experimentally, SrRuO films remain metallic even for a thickness
of 2 unit cells (uc), but the Curie temperature, T, starts to decrease at 4
uc and becomes zero at 2 uc. Using the Stoner model, we attributed the T
decrease to a decrease in the density of states (N). Namely, in the thin
film geometry, the hybridized Ru-d orbitals are terminated by top and
bottom interfaces, resulting in quantum confinement and reduction of N.Comment: 20 pages, 4 figure
Orbital-selective confinement effect of Ru orbitals in SrRuO ultrathin film
The electronic structure of SrRuO thin film with thickness from 50 to 1
unit cell (u.c.) is investigated via the resonant inelastic x-ray scattering
(RIXS) technique at the O K-edge to unravel the intriguing interplay of orbital
and charge degrees of freedom. We found that orbital-selective quantum
confinement effect (QCE) induces the splitting of Ru orbitals. At the same
time, we observed a clear suppression of the electron-hole continuum across the
metal-to-insulator transition (MIT) occurring at the 4 u.c. sample. From these
two clear observations we conclude that QCE gives rise to a Mott insulating
phase in ultrathin SrRuO films. Our interpretation of the RIXS spectra is
supported by the configuration interaction calculations of RuO clusters.Comment: 7 pages, 7 figure
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