6,650 research outputs found
Theory of Core-Level Photoemission and the X-ray Edge Singularity Across the Mott Transition
The zero temperature core-level photoemission spectrum is studied across the
metal to Mott insulator transition using dynamical mean-field theory and
Wilson's numerical renormalization group. An asymmetric power-law divergence is
obtained in the metallic phase with an exponent alpha(U,Q)-1 which depends on
the strength of both the Hubbard interaction U and the core-hole potential Q.
For Q <~ U_c/2 alpha decreases with increasing U and vanishes at the transition
(U -> U_c) leading to a symmetric peak in the insulating phase. For Q >~ U_c/2,
alpha remains finite close to the transition, but the integrated intensity of
the power-law vanishes and there is no associated peak in the insulator. The
weight and position of the remaining peaks in the spectra can be understood
within a molecular orbital approach.Comment: 5 pages, 6 figure
Development of a general time-dependent absorbing potential for the constrained adiabatic trajectory method
The Constrained Adiabatic Trajectory Method (CATM) allows us to compute
solutions of the time-dependent Schr\"odinger equation using the Floquet
formalism and Fourier decomposition, using matrix manipulation within a
non-orthogonal basis set, provided that suitable constraints can be applied to
the initial conditions for the Floquet eigenstate. A general form is derived
for the inherent absorbing potential, which can reproduce any dispersed
boundary conditions. This new artificial potential acting over an additional
time interval transforms any wavefunction into a desired state, with an error
involving exponentially decreasing factors. Thus a CATM propagation can be
separated into several steps to limit the size of the required Fourier basis.
This approach is illustrated by some calculations for the molecular ion
illuminated by a laser pulse.Comment: 8 pages, 7 figure
Origin of the high Neel temperature in SrTcO3
We investigate the origin of the high Neel temperature recently found in Tc
perovskites. The electronic structure in the magnetic state of SrTcO3 and its
3d analogue SrMnO3 is calculated within a framework combining band-structure
and many-body methods. In agreement with experiment, the Neel temperature of
SrTcO3 is found to be four times larger than that of SrMnO3. We show that this
is because the Tc-compound lies on the verge of the itinerant-to-localized
transition, and also has a larger bandwidth, while the Mn-compound lies deeper
into the localized side. For SrTcO3 we predict that the Neel temperature
depends weakly on applied pressure, in clear violation of Bloch's rule,
signaling the complete breakdown of the localized picture.Comment: 4+ pages, 3 figures, published versio
Universality and Critical Behavior at the Mott transition
We report conductivity measurements of Cr-doped V2O3 using a variable
pressure technique. The critical behavior of the conductivity near the
Mott-insulator to metal critical endpoint is investigated in detail as a
function of pressure and temperature. The critical exponents are determined, as
well as the scaling function associated with the equation of state. The
universal properties of a liquid-gas transition are found. This is potentially
a generic description of the Mott critical endpoint in correlated electron
materials.Comment: 3 figure
Global integration of the Schr\"odinger equation within the wave operator formalism: The role of the effective Hamiltonian in multidimensional active spaces
A global solution of the Schr\"odinger equation, obtained recently within the
wave operator formalism for explicitly time-dependent Hamiltonians [J. Phys. A:
Math. Theor. 48, 225205 (2015)], is generalized to take into account the case
of multidimensional active spaces. An iterative algorithm is derived to obtain
the Fourier series of the evolution operator issuing from a given
multidimensional active subspace and then the effective Hamiltonian
corresponding to the model space is computed and analysed as a measure of the
cyclic character of the dynamics. Studies of the laser controlled dynamics of
diatomic models clearly show that a multidimensional active space is required
if the wavefunction escapes too far from the initial subspace. A suitable
choice of the multidimensional active space, including the initial and target
states, increases the cyclic character and avoids divergences occuring when
one-dimensional active spaces are used. The method is also proven to be
efficient in describing dissipative processes such as photodissociation.Comment: 33 pages, 11 figure
Heavy-fermion and spin-liquid behavior in a Kondo lattice with magnetic frustration
We study the competition between the Kondo effect and frustrating exchange
interactions in a Kondo-lattice model within a large- dynamical
mean-field theory. We find a T=0 phase transition between a heavy Fermi-liquid
and a spin-liquid for a critical value of the exchange , the
single-impurity Kondo temperature. Close to the critical point, the Fermi
liquid coherence scale is strongly reduced and the effective mass
strongly enhanced. The regime is characterized by spin-liquid
magnetic correlations and non-Fermi-liquid properties. It is suggested that
magnetic frustration is a general mechanism which is essential to explain the
large effective mass of some metallic compounds such as LiVO.Comment: 7 pages, 1 figure. Late
An experimental study of wine consumers’ willingness to pay for environmental characteristics
The reduction of pesticides use is becoming a priority for the public authorities in many countries. We conducted an experiment with wine consumers to see whether end-consumers value the dissemination of information about environmentally-friendly production practices. The experiment was devised to (i) evaluate whether there is a premium for environmentally-friendly wines, (ii) determine whether or not consumers are sensitive to label owners who implement and guarantee the environmental actions, (iii) and assess the impact of public messages about the consequences of pesticide use. Some 139 participants were divided randomly into two groups. One group had no specific information about the current state of pesticide use in farming. The other group was given information about pesticide use in farming before making their valuations. Becker-DeGroot-Marshak mechanisms revealed that (i) the environmental signal is valued differently depending on who conveyed the information, and that (ii)dissemination of information about the environmental repercussions of farming methods does not significantly affect willingness-to-pay.Willingness to pay, Wine, Effect of information, Experimental economics, Environment, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,
Constrained Adiabatic Trajectory Method (CATM): a global integrator for explicitly time-dependent Hamiltonians
The Constrained Adiabatic Trajectory Method (CATM) is reexamined as an
integrator for the Schr\"odinger equation. An initial discussion places the
CATM in the context of the different integrators used in the literature for
time-independent or explicitly time-dependent Hamiltonians. The emphasis is put
on adiabatic processes and within this adiabatic framework the interdependence
between the CATM, the wave operator, the Floquet and the (t,t') theories is
presented in detail. Two points are then more particularly analysed and
illustrated by a numerical calculation describing the ion submitted to
a laser pulse. The first point is the ability of the CATM to dilate the
Hamiltonian spectrum and thus to make the perturbative treatment of the
equations defining the wave function possible, possibly by using a Krylov
subspace approach as a complement. The second point is the ability of the CATM
to handle extremely complex time-dependencies, such as those which appear when
interaction representations are used to integrate the system.Comment: 15 pages, 14 figure
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