43,311 research outputs found
Scaling Between Periodic Anderson and Kondo Lattice Models
Continuous-Time Quantum Monte Carlo (CT-QMC) method combined with Dynamical
Mean Field Theory (DMFT) is used to calculate both Periodic Anderson Model
(PAM) and Kondo Lattice Model (KLM). Different parameter sets of both models
are connected by the Schrieffer-Wolff transformation. For degeneracy N=2, a
special particle-hole symmetric case of PAM at half filling which always fixes
one electron per impurity site is compared with the results of the KLM. We find
a good mapping between PAM and KLM in the limit of large on-site Hubbard
interaction U for different properties like self-energy, quasiparticle residue
and susceptibility. This allows us to extract quasiparticle mass
renormalizations for the f electrons directly from KLM. The method is further
applied to higher degenerate case and to realsitic heavy fermion system CeRhIn5
in which the estimate of the Sommerfeld coefficient is proven to be close to
the experimental value
Modular Invariance for Twisted Modules over a Vertex Operator Superalgebra
The purpose of this paper is to generalize Zhu's theorem about characters of
modules over a vertex operator algebra graded by integer conformal weights, to
the setting of a vertex operator superalgebra graded by rational conformal
weights. To recover SL_2(Z)-invariance of the characters it turns out to be
necessary to consider twisted modules alongside ordinary ones. It also turns
out to be necessary, in describing the space of conformal blocks in the
supersymmetric case, to include certain `odd traces' on modules alongside
traces and supertraces. We prove that the set of supertrace functions, thus
supplemented, spans a finite dimensional SL_2(Z)-invariant space. We close the
paper with several examples.Comment: 42 pages. Published versio
Hexagonal Rare-Earth Manganites as Promising Photovoltaics and Light Polarizers
Ferroelectric materials possess a spontaneous electric polarization and may
be utilized in various technological applications ranging from non-volatile
memories to solar cells and light polarizers. Recently, hexagonal rare-earth
manganites, h-RMnO (R is a rare-earth ion) have attracted considerable
interest due to their intricate multiferroic properties and improper
ferroelectricity characterized by a sizable remnant polarization and high Curie
temperature. Here, we demonstrate that these compounds can serve as very
efficient photovoltaic materials and, in addition, possess remarkable optical
anisotropy properties. Using first-principles methods based on
density-functional theory and considering h-TbMnO as a representative
manganite, we predict a strong light absorption of this material in the solar
spectrum range, resulting in the maximum light-to-electricity energy conversion
efficiency up to 33%. We also predict an extraordinary optical linear dichroism
and linear birefringence properties of h-TbMnO in a broad range of optical
frequencies. These results uncover the unexplored potential of hexagonal
rare-earth manganites to serve as photovoltaics in solar cells and as
absorptive and birefringent light polarizers.Comment: 26 pages, 8 figure
Z-graded weak modules and regularity
It is proved that if any Z-graded weak module for vertex operator algebra V
is completely reducible, then V is rational and C_2-cofinite. That is, V is
regular. This gives a natural characterization of regular vertex operator
algebras.Comment: 9 page
Optical study of phase transitions in single-crystalline RuP
RuP single crystals of MnP-type orthorhombic structure were synthesized by
the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal
that the compound experiences two structural phase transitions, which are
further confirmed by enormous anomalies shown in temperature-dependent
resistivity and magnetic susceptibility. Particularly, the resistivity drops
monotonically upon temperature cooling below the second transition, indicating
that the material shows metallic behavior, in sharp contrast with the
insulating ground state of polycrystalline samples. Optical conductivity
measurements were also performed in order to unravel the mechanism of these two
transitions. The measurement revealed a sudden reconstruction of band structure
over a broad energy scale and a significant removal of conducting carriers
below the first phase transition, while a charge-density-wave-like energy gap
opens below the second phase transition.Comment: 5 pages, 6 figure
An approach for integrating multimodal omics data into sparse and interpretable models.
Using omics data, a common goal is to identify a concise set of variables that predict a clinical endpoint from an extensive pool. In a recent paper published in Nature Biotechnology, HĂ©dou et al. <sup>1</sup> introduced Stabl, a computational method crafted to identify sparse yet robust signatures linked to endpoints
Deuteron and proton NMR study of Dâ, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases
The solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric field gradient (FZZ) is obtained from the dideuterium spectrum. A double Maier-Saupe potential (MSMS) is used to rationalize the order parameters of pdcb. The liquid-crystal fields Gâ and Gâ are taken to be due to size and shape interactions and interactions between the solute molecular quadrupole and the mean FZZ of the medium. The FZZâs obtained from Dâ and Gâ (from pdcb) are compared and discussed
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