698 research outputs found
Edge Modes in the Intermediate-D and Large-D Phases of the S=2 Quantum Spin Chain with XXZ and On-Site Anisotropies
We investigate the edge modes at T=0 in the intermediate-D (ID) phase and the
large-D (LD) phase of the S=2 quantum spin chain with the XXZ anisotropy and
the generalized on-site anisotropies by use of the DMRG. There exists a gapless
edge mode in the ID phase, while no gapless edge mode in the LD phase. These
results are consistent with the physical pictures of these phases. We also show
the ground-state phase diagrams obtained by use of the exact diagonalization
and the level spectroscopy analysis.Comment: Submitted to "Proceedings of the International Conference on Strongly
Correlated Electron Systems (SCES2013)
Anomalous behavior of the spin gap of a spin-1/2 two-leg antiferromagnetic ladder with Ising-like rung interactions
Using mainly numerical methods, we investigate the width of the spin gap of a
spin-1/2 two-leg ladder described by \cH= J_\rl \sum_{j=1}^{N/2} [ \vS_{j,a}
\cdot \vS_{j+1,a} + \vS_{j,b} \cdot \vS_{j+1,b} ] + J_\rr \sum_{j=1}^{N/2}
[\lambda (S^x_{j,a} S^x_{j,b} + S^y_{j,a} S^y_{j,b}) + S^z_{j,a} S^z_{j,b}] ,
where denotes the -component of the spin-1/2
operator at the -th site of the chain. We mainly focus on the J_\rr
\gg J_\rl > 0 and case. The width of the spin gap as a
function of anomalously increases near ; for instance,
for when . The gap formation
mechanism is thought to be different for the
cases. Since, in usual cases, the width of the gap becomes zero or small at the
point where the gap formation mechanism changes, the above gap-increasing
phenomenon in the present case is anomalous. We explain the origin of this
anomalous phenomenon by use of the degenerate perturbation theory. We also draw
the ground-state phase diagram.Comment: 4 pages, 11 figures; Proc. "The International Conference on Quantum
Criticality and Novel Phases" (2012), to be published in Phys. Stat. Solidi
RESOLVING THE CLUMPY STRUCTURE OF THE OUTFLOW WINDS IN THE GRAVITATIONALLY LENSED QUASAR SDSS J1029+2623
We study the geometry and the internal structure of the outflowing wind from the accretion disk of a quasar by observing multiple sightlines with the aid of strong gravitational lensing. Using Subaru/High Dispersion Spectrograph, we performed high-resolution (R ~ 36,000) spectroscopic observations of images A and B of the gravitationally lensed quasar SDSS J1029+2623 (at z em ~ 2.197) whose image separation angle, θ ~ 22.''5, is the largest among those discovered so far. We confirm that the difference in absorption profiles in images A and B discovered by Misawa et al. has remained unchanged since 2010, implying the difference is not due to time variability of the absorption profiles over the delay between the images, Δt ~ 744 days, but rather due to differences along the sightlines. We also discovered a time variation of C IV absorption strength in both images A and B due to a change in the ionization condition. If a typical absorber's size is smaller than its distance from the flux source by more than five orders of magnitude, it should be possible to detect sightline variations among images of other smaller separation, galaxy-scale gravitationally lensed quasars.ArticleAstrophys. J. Lett. 794(2):L20 (2014)journal articl
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