691 research outputs found
Energy Versus Magnetic-Field Diagram of the Spin-1 Haldane System with an Impurity
Energy versus magnetic-field diagram of the spin- Haldane system with an
impurity bond is studied in terms of spin-1/2 degree of freedom at the sites
neighboring the impurity bond by means of analytical method. We examine the
equivalence between the realistic Hamiltonian and the phenomenological
Hamiltonian which is composed two spin-1/2 spins representing the spin-1/2
degree of freedom. It is proved that when the strength of the impurity bond is
sufficiently weak, the two Hamiltonians are equivalent to each other, as far as
the energies of the low-lying states are concerned. We determine the
correspondence between the interaction constants in the phenomenological
Hamiltonian and those in the realistic Hamiltonian.Comment: 10 pages, plain TeX (Postscript figures are included), KU-CCS-93-00
Phase Diagram of Adsorbate-Induced Row-Type-Alignments
The phase diagram of adsorbate-induced row-type-alignments, such as
missing-row reconstructions induced by adsorbate-atoms on the FCC(110) surface,
is calculated by the Blume-Emmery-Griffiths (BEG) model. In the model, we
introduce adatom-adatom and dipole-dipole interactions between nearest-neighbor
(NN) and next-nearest-neighbor (NNN) rows. The calculation of the temperature
versus adatom chemical potential phase diagram is performed using mean-field
approximation. It is indicated that when NN and NNN interactions are
competitive, there appear either dipole or coverage modulated (incommensurate)
phases at high temperatures for wide regime of the interactions.Comment: 5 pages, 6 figures, ICSOS'99. to appear in Surf. Rev. and Let
Ground-State Phase Diagram of Frustrated Anisotropic Quantum Spin Chains
Recent studies on the frustrated quantum spin chains with easy-plane
anisotropy are reviewed. We are particularly interested in novel "chiral"
phases characterized by the spontaneous breaking of the parity symmetry. The
ground-state phase diagrams of the chains are discussed.Comment: 6 pages (ptptex.sty), 3 figures, to appear in Prog. Theor. Phys.
Suppl. (Proc. of the 16th Nishinomiya-Yukawa Symposium and YITP International
Workshop, Nov. 2001
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)
Observation of zigzag and armchair edges of graphite using scanning tunneling microscopy and spectroscopy
The presence of structure-dependent edge states of graphite is revealed by
both ambient- and ultra-highvacuum- (UHV) scanning tunneling microscopy (STM) /
scanning tunneling spectroscopy (STS) observations. On a hydrogenated zigzag
(armchair) edge, bright spots are (are not) observed together with (SQRT(3) by
SQRT(3))R30 superlattice near the Fermi level (V_S = −30 mV for a peak of
the local density of states (LDOS)) under UHV, demonstrating that a zigzag edge
is responsible for the edge states, although there is no appreciable difference
between as-prepared zigzag and armchair edges in air. Even in hydrogenated
armchair edge, however, bright spots are observed at defect points, at which
partial zigzag edges are created in the armchair edge.Comment: 4 pages, 4 figures, contents for experimental/theoretical reseachers,
accepted as an issue of Physical Review B (PRB
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