12,510 research outputs found
Supersolidity and phase diagram of softcore bosons in a triangular lattice
We study the softcore extended Bose Hubbard model in a two-dimensional
triangular lattice by using the quantum Monte Carlo methods. The ground state
phase diagram of the system exhibits a very fruitful structure. Except the Mott
insulating state, four kinds of solid states with respect to the commensurate
filling factors and are identified. Two of them (CDW II
and CDW III) are newly predicted. In incommensurate fillings, superfluid,
spuersolid as well as phase separation states are detected . As in the case for
the hardcore bosons, a supersolid phase exists in while it is
unstable towards the phase separation in . However, this instability
is refrained in due to the softening of the bosons and then a
supersolid phase survives.Comment: 4 pages, 5 figure
Temperature-resolution anomalies in the reconstruction of time dynamics from energy-loss experiments
Inelastic scattering techniques provide a powerful approach to studying
electron and nuclear dynamics, via reconstruction of a propagator that
quantifies the time evolution of a system. There is now growing interest in
applying such methods to very low energy excitations, such as lattice
vibrations, but in this limit the cross section is no longer proportional to a
propagator. Significant deviations occur due to the finite temperature Bose
statistics of the excitations. Here we consider this issue in the context of
high-resolution electron energy loss experiments on the copper-oxide
superconductor BiSrCaCuO. We find that simple division of a
Bose factor yields an accurate propagator on energy scales greater than the
resolution width. However, at low energy scales, the effects of resolution and
finite temperature conspire to create anomalies in the dynamics at long times.
We compare two practical ways for dealing with such anomalies, and discuss the
range of validity of the technique in light of this comparison.Comment: 19 pages, 2 figures, submitted to Journal of Physics
Quantum Renormalization of the Spin Hall Effect
By quantum Monte Carlo simulation of a realistic multiorbital Anderson
impurity model, we study the spin-orbit interaction (SOI) of an Fe impurity in
Au host metal. We show, for the first time, that the SOI is strongly
renormalized by the quantum spin fluctuation. Based on this mechanism, we can
explain why the gigantic spin Hall effect in Au with Fe impurities was observed
in recent experiment, while it is not visible in the anomalous Hall effect. In
addition, we show that the SOI is strongly renormalized by the Coulomb
correlation U. Based on this picture, we can explain past discrepancies in the
calculated orbital angular momenta for an Fe impurity in an Au host.Comment: 4 pages, 3 figure
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