372 research outputs found
Numerical Study of Photo-Induced Dynamics in Double-Exchange Model
Photo-induced spin and charge dynamics in double-exchange model are
numerically studied. The Lanczos method and the density-matrix
renormalization-group method are applied to one-dimensional finite-size
clusters. By photon irradiation in a charge ordered (CO) insulator associated
with antiferromagnetic (AFM) correlation, both the CO and AFM correlations
collapse rapidly, and appearances of new peaks inside of an insulating gap are
observed in the optical spectra and the one-particle excitation spectra. Time
evolutions of the spin correlation and the in-gap state are correlated with
each other, and are governed by the transfer integral of conduction electrons.
Results are interpreted by the charge kink/anti-kink picture and their
effective motions which depend on the localized spin correlation. Pump-photon
density dependence of spin and charge dynamics are also studied. Roles of spin
degree of freedom are remarkable in a case of weak photon density. Implications
of the numerical results for the pump-probe experiments in perovskite
manganites are discussed.Comment: 16 pages, 16 figure
Relaxation Dynamics of Photocarriers in One-Dimensional Mott Insulators Coupled to Phonons
We examine recombination processes of photocarriers in one-dimensional Mott
insulators coupled to phonons. Performing density matrix renormalization group
calculations, we find that, even for small electron-phonon coupling, many
phonons are generated dynamically, which cause initial relaxation process after
the irradiation. At the same time, spin-charge coupling coming from mixing of
high- and low-energy states by the irradiation is suppressed. We discuss
differences between Mott and band insulators in terms of relaxation dynamics.Comment: 5 pages, 3 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
Electron-phonon coupling and spin-charge separation in one-dimensional Mott insulators
We examine the single-particle excitation spectrum in the one-dimensional
Hubbard-Holstein model at half-filling by performing the dynamical density
matrix renormalization group (DDMRG) calculation. The DDMRG results are
interpreted as superposition of spectra for a spinless carrier dressed with
phonons. The superposition is a consequence of robustness of the spin-charge
separation against electron-phonon coupling. The separation is in contrast to
the coupling between phonon and spin degrees of freedom in two-dimensional
systems. We discuss implication of the results of the recent angle-resolved
photoemission spectroscopy measurements on SrCuO.Comment: 5 pages, 4 figures. submitted to the Physical Review Letter
Liver Involvement with Acute Myeloid Leukemia
Liver involvement with acute myeloid leukemia (AML) is rarely reported. The majority of published cases suggest a cholestatic picture and obstructive jaundice at presentation. On the contrary, our patient presented with transaminitis without cholestasis. Elevated liver function tests persisted in our patient despite cholecystectomy; however, they normalized with chemotherapy administration, suggesting that AML was the causative effect of the hepatitis-like picture. Our review of the literature revealed that most reported cases of AML with liver involvement had short-lived remissions and an overall ominous prognosis. In our opinion, patients who have liver involvement with AML should be offered alternative investigational therapies with a low hepatic toxicity profile
The sensitivity of Euro-Atlantic regimes to model horizontal resolution
There is growing evidence that the atmospheric dynamics of the Euro-Atlantic sector during winter is driven in part by the presence of quasi-persistent regimes. However, general circulation models typically struggle to simulate these with, for example, an overly weakly persistent blocking regime. Previous studies have showed that increased horizontal resolution can improve the regime structure of a model but have so far only considered a single model with only one ensemble member at each resolution, leaving open the possibility that this may be either coincidental or model dependent. We show that the improvement in regime structure due to increased resolution is robust across multiple models with multiple ensemble members. However, while the high-resolution models have notably more tightly clustered data, other aspects of the regimes may not necessarily improve and are also subject to a large amount of sampling variability that typically requires at least three ensemble members to surmount
Photoinduced charge and spin dynamics in strongly correlated electron systems
Motivated by photoinduced phase transition in manganese oxides, charge and
spin dynamics induced by photoirradiation are examined. We calculate the
transient optical absorption spectra of the extended double-exchange model by
the density matrix renormalization group (DMRG) method. A charge-ordered
insulating (COI) state becomes metallic just after photoirradiation, and the
system tends to recover the initial COI state. The recovery is accompanied with
remarkable suppression of an antiferromagnetic correlation in the COI state.
The DMRG results are consistent with recent pump-probe spectroscopy data.Comment: 5 pages, 4 figure
Generation of maximum spin entanglement induced by cavity field in quantum-dot systems
Equivalent-neighbor interactions of the conduction-band electron spins of
quantum dots in the model of Imamoglu et al. [Phys. Rev. Lett. 83, 4204 (1999)]
are analyzed. Analytical solution and its Schmidt decomposition are found and
applied to evaluate how much the initially excited dots can be entangled to the
remaining dots if all of them are initially disentangled. It is demonstrated
that the perfect maximally entangled states (MES) can only be generated in the
systems of up to 6 dots with a single dot initially excited. It is also shown
that highly entangled states, approximating the MES with a good accuracy, can
still be generated in systems of odd number of dots with almost half of them
being excited. A sudden decrease of entanglement is observed by increasing the
total number of dots in a system with a fixed number of excitations.Comment: 6 pages, 7 figures, to appear in Phys. Rev.
Complete eigenstates of identical qubits arranged in regular polygons
We calculate the energy eigenvalues and eigenstates corresponding to coherent
single and multiple excitations of an array of N identical qubits or two-level
atoms (TLA's) arranged on the vertices of a regular polygon. We assume only
that the coupling occurs via an exchange interaction which depends on the
separation between the qubits. We include the interactions between all pairs of
qubits, and our results are valid for arbitrary distances relative to the
radiation wavelength. To illustrate the usefulness of these states, we plot the
distance dependence of the decay rates of the n=2 (biexciton) eigenstates of an
array of 4 qubits, and tabulate the biexciton eigenvalues and eigenstates, and
absorption frequencies, line widths, and relative intensities for polygons
consisting of N=2,...,9 qubits in the long-wavelength limit.Comment: Added a figure showing how these results can be used to compute
deviations from "equal collective decoherence" approximation
Effects of acotiamide on esophageal motor function and gastroesophageal reflux in healthy volunteers
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