7,520 research outputs found
Equation of State of the Fermionic 2D Hubbard Model
We present results for the equation of state of the two-dimensional Hubbard
model on an isotropic square lattice as obtained from a controlled and
numerically exact large-cluster dynamical mean field simulation. Our results
are obtained for large but finite systems and are extrapolated to infinite
system size using a known finite size scaling relation. We present the energy,
entropy, double occupancy and nearest-neighbour spin correlations extrapolated
to the thermodynamic limit and discuss the implications of these calculations
on pseudogap physics of the 2D-Hubbard model away from half filling. We find a
strong behavioural shift in energy below a temperature which becomes more
pronounced for larger clusters. Finally, we provide reference calculations and
tables for the equation of state for values of doping away from half filling
which are of interest to cold atom experiments.Comment: 8 pages 6 figures - See Source for Supplementary Material File
Dielectric screening of surface states in a topological insulator
Hexagonal warping provides an anisotropy to the dispersion curves of the
helical Dirac fermions that exist at the surface of a topological insulator. A
sub-dominant quadratic in momentum term leads to an asymmetry between
conduction and valence band. A gap can also be opened through magnetic doping.
We show how these various modifications to the Dirac spectrum change the
polarization function of the surface states and employ our results to discuss
their effect on the plasmons. In the long wavelength limit, the plasmon
dispersion retains its square root dependence on its momentum,
, but its slope is modified and it can acquire a weak
dependence on the direction of . Further, we find the existence
of several plasmon branches, one which is damped for all values of
, and extract the plasmon scattering rate for a representative
case.Comment: 11 pages, 8 figure
The new Toulouse-Geneva Stellar Evolution Code including radiative accelerations of heavy elements
Atomic diffusion has been recognized as an important process that has to be
considered in any computations of stellar models. In solar-type and cooler
stars, this process is dominated by gravitational settling, which is now
included in most stellar evolution codes. In hotter stars, radiative
accelerations compete with gravity and become the dominant ingredient in the
diffusion flux for most heavy elements. Introducing radiative accelerations
into the computations of stellar models modifies the internal element
distribution and may have major consequences on the stellar structure. Coupling
these processes with hydrodynamical stellar motions has important consequences
that need to be investigated in detail. We aim to include the computations of
radiative accelerations in a stellar evolution code (here the TGEC code) using
a simplified method (SVP) so that it may be coupled with sophisticated
macroscopic motions. We also compare the results with those of the Montreal
code in specific cases for validation and study the consequences of these
coupled processes on accurate models of A- and early-type stars. We implemented
radiative accelerations computations into the Toulouse-Geneva stellar evolution
code following the semi-analytical prescription proposed by Alecian and
LeBlanc. This allows more rapid computations than the full description used in
the Montreal code. We present results for A-type stellar models computed with
this updated version of TGEC and compare them with similar published models
obtained with the Montreal evolution code. We discuss the consequences for the
coupling with macroscopic motions, including thermohaline convection.Comment: 12 pages, 13 figures, published in A&
opendf - an implementation of the dual fermion method for strongly correlated systems
The dual fermion method is a multiscale approach for solving lattice problems
of interacting strongly correlated systems. In this paper, we present the
\texttt{opendf} code, an open-source implementation of the dual fermion method
applicable to fermionic single-orbital lattice models in dimensions
and . The method is built on a dynamical mean field starting point, which
neglects all local correlations, and perturbatively adds spatial correlations.
Our code is distributed as an open-source package under the GNU public license
version 2.Comment: 7 pages, 6 figures, 28th Annual CSP Workshop proceeding
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