12 research outputs found
Supersolid of Hardcore Bosons on the Face Centered Cubic Lattice
We investigate a supersolid state in hardcore boson models on the
face-centered-cubic (FCC) lattice. The supersolid state is characterized by a
coexistence of crystalline order and superfluidity. Using a quantum Monte Carlo
method based on the directed-loop algorithm, we calculate static structure
factors and superfluid density at finite temperature, from which we obtain the
phase diagram. The supersolid phase exists at intermediate fillings between a
three-quarter-filled solid phase and a half-filled solid phase. We also discuss
the mechanism of the supersolid state on the FCC lattice.Comment: 5pages, 6figure
Field-induced incommensurate order for the quasi-one-dimensional XXZ model in a magnetic field
We investigate phase transitions of the quasi-one-dimensional XXZ model in a
magnetic field, using the bosonization combined with the mean field treatment
of the inter-chain interaction. We then find that the field induced
incommensurate order is certainly realized in the low field region, while the
transverse staggered order appears in the high field region. On the basis of
the result, we discuss the field-induced phase transition recently observed for
BaCo2V2O8.Comment: 6 pages, 3 figures, to appear in PR
Magnetic properties of the spin-1/2 XXZ model on the Shastry-Sutherland lattice: Effect of long-range interactions
We study magnetic properties of the Ising-like XXZ model on the
Shastry-Sutherland lattices with long-range interactions, using the quantum
Monte Carlo method. This model shows magnetization plateau phases at one-half
and one-third of the saturation magnetization when additional couplings are
considered. We investigate the finite temperature transition to one-half and
one-third plateau phases. The obtained results suggest that the former case is
of the first order and the latter case is of the second order. We also find
that the system undergoes two successive transitions with the 2D Ising model
universality, although there is a single phase transition in the Ising limit
case. Finally, we estimate the coupling ratio to explain the magnetization
process observed in Comment: 5 pages, 6 figure
NMR relaxation of quantum spin chains in magnetic fields
We investigate NMR relaxation rates 1/T_1 of quantum spin chains in magnetic
fields. Universal properties for the divergence behavior of 1/T_1 are obtained
in the Tomonaga-Luttinger-liquid state. The results are discussed in comparison
with experimental results.Comment: 5 pages, 3 figure
Dynamical properties of S=1 bond-alternating Heisenberg chains in transverse magnetic fields
We calculate dynamical structure factors of the S=1 bond-alternating
Heisenberg chain with a single-ion anisotropy in transverse magnetic fields,
using a continued fraction method based on the Lanczos algorithm. In the
Haldane-gap phase and the dimer phase, dynamical structure factors show
characteristic field dependence. Possible interpretations are discussed. The
numerical results are in qualitative agreement with recent results for
inelastic neutron-scattering experiments on the S=1 bond-alternating
Heisenberg-chain compound and the
S=1 Haldane-gap compound in
transverse magnetic fields.Comment: 7 pages, 6 figure
Dynamical properties of S=1 bond-alternating Heisenberg chains at finite temperatures
Dynamical structure factors of the S=1 bond-alternating spin chains in the
dimer phase are calculated at finite temperature, using the pair dynamical
correlated-effective-field approximation. At T=0, the delta-function-type peak
of the one-magnon mode appears. When temperature is increased, such a sharp
peak is broadened and the additional weak peak caused by the excitation from
the triplet state to the quintet state emerges in the higher energy region. The
results are discussed in comparison with those obtained by the exact
diagonalization method.Comment: 5 pages, 4 figure
Incommensurate state in a quasi-one-dimensional bond-alternating antiferromagnet with frustration in magnetic fields
We investigate the critical properties of the bond-alternating spin
chain with a next-nearest-neighbor interaction in magnetic fields. By the
numerical calculation and the exact solution based on the effective
Hamiltonian, we show that there is a parameter region where the longitudinal
incommensurate spin correlation becomes dominant around the half-magnetization
of the saturation. Possible interpretations of our results are discussed. We
next investigate the effects of the interchain interaction (). The
staggered susceptibility and the uniform magnetization are calculated by
combining the density-matrix renormalization group method with the interchain
mean-field theory. For the parameters where the dominant longitudinal
incommensurate spin correlation appears in the case , the
staggered long-range order does not emerge up to a certain critical value of
around the half-magnetization of the saturation. We calculate the
static structure factor in such a parameter region. The size dependence of the
static structure factor at implies that the system has a
tendency to form an incommensurate long-range order around the
half-magnetization of the saturation. We discuss the recent experimental
results for the NMR relaxation rate in magnetic fields performed for
pentafluorophenyl nitronyl nitroxide.Comment: 10 pages, 12 figures, final version, to appear in PRB vol. 70, No. 5
(2004
Laparoscopic Partial Hepatectomy of Focal Nodular Hyperplasia
Focal nodular hyperplasia is a benign liver lesion incidentally discovered with increasing frequency because of the proliferation of imaging studies. Radiographic characterization can diagnose this pathologic lesion and nonoperative therapy is the standard of care. However, surgical resection may be required for diagnostic reasons or symptomatic patients. Depending on the anatomic location of the lesion, biopsy and/or resection can be performed laparoscopically. We herein report the case of a 26-year-old Japanese woman with a hepatic tumor who required a medical examination. Her medical history was negative for alcohol abuse, oral contraceptive administration and trauma. Clinical examination showed no significant symptoms. Ultrasonography, computed tomography and magnetic resonance imaging showed a mass located in the left lateral segment of the liver with a diameter of about 40 mm. It was difficult to diagnose the tumor definitively from these imaging studies, so we performed laparoscopic partial hepatectomy with successive firing of endoscopic staplers. The histopathological diagnosis was focal nodular hyperplasia. Surgical procedures and postoperative course were uneventful and the patient was discharged from the hospital on postoperative day 5