1,935 research outputs found
Strength of the d_{x^2-y^2} pairing in the two-leg Hubbard ladder
In the ground state of the doped two-leg Hubbard ladder there are power-law
decaying d_{x^2-y^2}-type pairing correlations. It is important to know the
strength and the temperature scale of these correlations. For this purpose, we
have performed determinantal Quantum Monte Carlo (QMC) calculations of the
reducible particle-particle interaction in the Hubbard ladder. In this paper,
we report on these calculations and show that, at sufficiently low
temperatures, resonant particle-particle scattering takes place in the
d_{x^2-y^2} pairing channel for certain values of the model parameters. The QMC
data presented here indicate that the d_{x^2-y^2} pairing correlations are
strong in the Hubbard ladder.Comment: 5 pages, 5 figure
Emergence of charge order in a staggered loop-current phase of cuprate high-temperature superconductors
We study the emergence of charge ordered phases within a pi-loop current
(piLC) model for the pseudogap based on a three-band model for underdoped
cuprate superconductors. Loop currents and charge ordering are driven by
distinct components of the short-range Coulomb interactions: loop currents
result from the repulsion between nearest-neighbor copper and oxygen orbitals,
while charge order results from repulsion between neighboring oxygen orbitals.
We find that the leading piLC phase has an antiferromagnetic pattern similar to
previously discovered staggered flux phases, and that it emerges abruptly at
hole dopings p below the van Hove filling. Subsequent charge ordering
tendencies in the piLC phase reveal that diagonal d-charge density waves (dCDW)
are suppressed by the loop currents while axial order competes more weakly. In
some cases we find a wide temperature range below the loop-current transition,
over which the susceptibility towards an axial dCDW is large. In these cases,
short-range axial charge order may be induced by doping-related disorder. A
unique feature of the coexisting dCDW and piLC phases is the emergence of an
incommensurate modulation of the loop currents. If the dCDW is biaxial
(checkerboard) then the resulting incommensurate current pattern breaks all
mirror and time-reversal symmetries, thereby allowing for a polar Kerr effect
Anomalous temperature dependence of the single-particle spectrum in the organic conductor TTF-TCNQ
The angle-resolved photoemission spectrum of the organic conductor TTF-TCNQ
exhibits an unusual transfer of spectral weight over a wide energy range for
temperatures 60K<T<260K. In order to investigate the origin of this finding,
here we report numerical results on the single-particle spectral weight
A(k,omega) for the one-dimensional (1D) Hubbard model and, in addition, for the
1D extended Hubbard and the 1D Hubbard-Holstein models. Comparisons with the
photoemission data suggest that the 1D Hubbard model is not sufficient for
explaining the unusual T dependence, and the long-range part of the Coulomb
repulsion also needs to be included.Comment: 4 pages, 4 figure
Temperature dependence of spinon and holon excitations in one-dimensional Mott insulators
Motivated by the recent angle-resolved photoemission spectroscopy (ARPES)
measurements on one-dimensional Mott insulators, SrCuO and
NaVO, we examine the single-particle spectral weight
of the one-dimensional (1D) Hubbard model at half-filling. We are particularly
interested in the temperature dependence of the spinon and holon excitations.
For this reason, we have performed the dynamical density matrix renormalization
group and determinantal quantum Monte Carlo (QMC) calculations for the
single-particle spectral weight of the 1D Hubbard model. In the QMC data, the
spinon and holon branches become observable at temperatures where the
short-range antiferromagnetic correlations develop. At these temperatures, the
spinon branch grows rapidly. In the light of the numerical results, we discuss
the spinon and holon branches observed by the ARPES experiments on
SrCuO. These numerical results are also in agreement with the
temperature dependence of the ARPES results on NaVO.Comment: 8 pages, 8 figure
Absolute Dimensions and Apsidal Motion of the Young Detached System LT Canis Majoris
New high resolution spectra of the short period (P~1.76 days) young detached
binary LT CMa are reported for the first time. By combining the results from
the analysis of new radial velocity curves and published light curves, we
determine values for the masses, radii and temperatures as follows: M_1= 5.59
(0.20) M_o, R_1=3.56 (0.07) R_o and T_eff1= 17000 (500) K for the primary and
M_2=3.36 (0.14) M_o, R_2= 2.04 (0.05) R_o and T_eff2= 13140 (800) K for the
secondary. Static absorbtion features apart from those coming from the close
binary components are detected in the several spectral regions. If these
absorbtion features are from a third star, as the light curve solutions
support, its radial velocity is measured to be RV_3=70(8) km s^-1. The orbit of
the binary system is proved to be eccentric (e=0.059) and thus the apsidal
motion exists. The estimated linear advance in longitude of periastron
corresponds to an apsidal motion of U=694+/-5 yr for the system. The average
internal structure constant log k_2,obs=-2.53 of LT CMa is found smaller than
its theoretical value of log k_2,theo=-2.22 suggesting the stars would have
more central concentration in mass. The photometric distance of LT CMa
(d=535+/-45 pc) is found to be much smaller than the distance of CMa OB1
association (1150 pc) which rules out membership. A comparison with current
stellar evolution models for solar metallicity indicates that LT CMa (35 Myr)
is much older than the CMa OB1 association (3 Myr), confirming that LT CMa is
not a member of CMa OB1. The kinematical and dynamical analysis indicate LT CMa
is orbiting the Galaxy in a circular orbit and belongs to the young thin-disk
population.Comment: 19 pages, 6 figures and 6 tables, accepted for publication in
Publication of the Astronomical Society of Japa
Why is there a gender segregation in choosing occupation?
Since the globe is developing century by century, the working environment also changes in every era. Currently, the working of women and also female occupations has reached great importance among society around the world. Women are enterprising, flexible and productive beings while working and in constructing new ideas and they want also be recognized by the community. From past to the present women worked in a variety of fields and some of them also did work in some village areas within carrying their small infants. But this area altered and everything turned to modernized and we see more women working in towns and cities. However, there are big differences, such as income and the working environment. Actually the reason why the occupations differ may have different factors. The considering reasons may due to social norms and cultural backgrounds. People want to make a career what social perception expects from them. The social values define whether you will work by your gender or by your skills or opposite of your gender such as women in male-dominated occupations. One of the significant points here is that professions differ according to gender. This paper aims to research about how gender segregation occurred in occupations. Additionally, the research will analyse the perceptions of gender roles in society and also the pay gaps and different factors which have an influence on women's condition at work
Theory of spin and charge fluctuations in the Hubbard model
A self-consistent theory of both spin and charge fluctuations in the Hubbard
model is presented. It is in quantitative agreement with Monte Carlo data at
least up to intermediate coupling . It includes both
short-wavelength quantum renormalization effects, and long-wavelength thermal
fluctuations which can destroy long-range order in two dimensions. This last
effect leads to a small energy scale, as often observed in high temperature
superconductors. The theory is conserving, satisfies the Pauli principle and
includes three-particle correlations necessary to account for the incipient
Mott transition.Comment: J1K 2R1 10 pages, Revtex 3.0, 4 uuencoded postscript figures, report#
CRPS-93-4
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