1,987 research outputs found
Continuous-time Diffusion Monte Carlo and the Quantum Dimer Model
A continuous-time formulation of the Diffusion Monte Carlo method for lattice
models is presented. In its simplest version, without the explicit use of trial
wavefunctions for importance sampling, the method is an excellent tool for
investigating quantum lattice models in parameter regions close to generalized
Rokhsar-Kivelson points. This is illustrated by showing results for the quantum
dimer model on both triangular and square lattices. The potential energy of two
test monomers as a function of their separation is computed at zero
temperature. The existence of deconfined monomers in the triangular lattice is
confirmed. The method allows also the study of dynamic monomers. A finite
fraction of dynamic monomers is found to destroy the confined phase on the
square lattice when the hopping parameter increases beyond a finite critical
value. The phase boundary between the monomer confined and deconfined phases is
obtained.Comment: 4 pages, 4 figures, revtex; Added a figure showing the
confinement/deconfinement phase boundary for the doped quantum dimer mode
Field effect on surface states in a doped Mott-Insulator thin film
Surface effects of a doped thin film made of a strongly correlated material
are investigated both in the absence and presence of a perpendicular electric
field. We use an inhomogeneous Gutzwiller approximation for a single band
Hubbard model in order to describe correlation effects. For low doping, the
bulk value of the quasiparticle weight is recovered exponentially deep into the
slab, but with increasing doping, additional Friedel oscillations appear near
the surface. We show that the inverse correlation length has a power-law
dependence on the doping level. In the presence of an electrical field,
considerable changes in the quasiparticle weight can be realized throughout the
system. We observe a large difference (as large as five orders of magnitude) in
the quasiparticle weight near the opposite sides of the slab. This effect can
be significant in switching devices that use the surface states for transport
Orbital degeneracy as a source of frustration in LiNiO
Motivated by the absence of cooperative Jahn-Teller effect and of magnetic
ordering in LiNiO, a layered oxide with triangular planes, we study a
general spin-orbital model on the triangular lattice. A mean-field approach
reveals the presence of several singlet phases between the SU(4) symmetric
point and a ferromagnetic phase, a conclusion supported by exact
diagonalizations of finite clusters. We argue that one of the phases,
characterized by a large number of low-lying singlets associated to dimer
coverings of the triangular lattice, could explain the properties of LiNiO,
while a ferro-orbital phase that lies nearby in parameter space leads to a new
prediction for the magnetic properties of NaNiO.Comment: 18 pages, 17 figure
C Minor: a Semantic Publish/Subscribe Broker for the Internet of Musical Things
Semantic Web technologies are increasingly used in the Internet of Things due to their intrinsic propensity to foster interoperability among heterogenous devices and services. However, some of the IoT application domains have strict requirements in terms of timeliness of the exchanged messages, latency and support for constrained devices. An example of these domains is represented by the emerging area of the Internet of MusicalThings.InthispaperweproposeCMinor,aCoAP-based semantic publish/subscribe broker speci\ufb01cally designed to meet the requirements of Internet of Musical Things applications, but relevant for any IoT scenario. We assess its validity through a practical use case
Asymmetry between the electron- and hole-doped Mott transition in the periodic Anderson model
We study the doping driven Mott metal-insulator transition (MIT) in the
periodic Anderson model set in the Mott-Hubbard regime. A striking asymmetry
for electron or hole driven transitions is found. The electron doped MIT at
larger U is similar to the one found in the single band Hubbard model, with a
first order character due to coexistence of solutions. The hole doped MIT, in
contrast, is second order and can be described as the delocalization of
Zhang-Rice singlets.Comment: 18 pages, 19 figure
Quasiparticle spectral weights of Gutzwiller-projected high T_c superconductors
We analyze the electronic Green's functions in the superconducting ground
state of the t-J model using Gutzwiller-projected wave functions, and compare
them to the conventional BCS form. Some of the properties of the BCS state are
preserved by the projection: the total spectral weight is continuous around the
quasiparticle node and approximately constant along the Fermi surface. On the
other hand, the overall spectral weight is reduced by the projection with a
momentum-dependent renormalization, and the projection produces electron-hole
asymmetry in renormalization of the electron and hole spectral weights. The
latter asymmetry leads to the bending of the effective Fermi surface which we
define as the locus of equal electron and hole spectral weight.Comment: 6 pages, 5 figures; x-labels on Figs. 1 and 2 corrected, footnote on
particle number corrected, references adde
Electric field response of strongly correlated one-dimensional metals: a Bethe-Ansatz density functional theory study
We present a theoretical study on the response properties to an external
electric field of strongly correlated one-dimensional metals. Our investigation
is based on the recently developed Bethe-Ansatz local density approximation
(BALDA) to the density functional theory formulation of the Hubbard model. This
is capable of describing both Luttinger liquid and Mott-insulator correlations.
The BALDA calculated values for the static linear polarizability are compared
with those obtained by numerically accurate methods, such as exact (Lanczos)
diagonalization and the density matrix renormalization group, over a broad
range of parameters. In general BALDA linear polarizabilities are in good
agreement with the exact results. The response of the exact exchange and
correlation potential is found to point in the same direction of the perturbing
potential. This is well reproduced by the BALDA approach, although the fine
details depend on the specific parameterization for the local approximation.
Finally we provide a numerical proof for the non-locality of the exact exchange
and correlation functional.Comment: 8 pages and 8 figure
Evolution of the single-hole spectral function across a quantum phase transition in the anisotropic-triangular-lattice antiferromagnet
We study the evolution of the single-hole spectral function when the ground
state of the anisotropic-triangular-lattice antiferromagnet changes from the
incommensurate magnetically-ordered phase to the spin-liquid state. In order to
describe both of the ground states on equal footing, we use the large-N
approach where the transition between these two phases can be obtained by
controlling the quantum fluctuations via an 'effective' spin magnitude. Adding
a hole into these ground states is described by a t-J type model in the
slave-fermion representation. Implications of our results to possible future
ARPES experiments on insulating frustrated magnets, especially CsCuCl,
are discussed.Comment: 8 pages, 7 figure
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