14,843 research outputs found
The CP-PACS Project and Lattice QCD Results
The aim of the CP-PACS project was to develop a massively parallel computer
for performing numerical research in computational physics with primary
emphasis on lattice QCD. The CP-PACS computer with a peak speed of 614 GFLOPS
with 2048 processors was completed in September 1996, and has been in full
operation since October 1996. We present an overview of the CP-PACS project and
describe characteristics of the CP-PACS computer. The CP-PACS has been mainly
used for hadron spectroscopy studies in lattice QCD. Main results in lattice
QCD simulations are given.Comment: 10 pages, 5 figures, Talk at the 5th International Conference on
Computational Physics (ICCP5), 11-13 October, 1999, Kanazawa, to appear in
Prog. Theor. Phys. (Suppl.) No. 138 (2000
Weyl semimetal phase in non-centrosymmetric transition metal monophosphides
Based on first principle calculations, we show that a family of nonmagnetic
materials including TaAs, TaP, NbAs and NbP are Weyl semimetal (WSM) without
inversion center. We find twelve pairs of Weyl points in the whole Brillouin
zone (BZ) for each of them. In the absence of spin-orbit coupling (SOC), band
inversions in mirror invariant planes lead to gapless nodal rings in the
energy-momentum dispersion. The strong SOC in these materials then opens full
gaps in the mirror planes, generating nonzero mirror Chern numbers and Weyl
points off the mirror planes. The resulting surface state Fermi arc structures
on both (001) and (100) surfaces are also obtained and show interesting shapes,
pointing to fascinating playgrounds for future experimental studies.Comment: Updated with k.p model analysis and a movie demonstrating
distribution of nodal rings and Weyl points, 19 pages, 4 figures and 1 tabl
Transition-Metal Pentatelluride ZrTe and HfTe: a Paradigm for Large-gap Quantum Spin Hall Insulators
Quantum spin Hall (QSH) insulators, a new class of quantum matters, can
support topologically protected helical edge modes inside bulk insulating gap,
which can lead to dissipationless transport. A major obstacle to reach wide
application of QSH is the lack of suitable QSH compounds, which should be
easily fabricated and has large size of bulk gap. Here we predict that single
layer ZrTe and HfTe are the most promising candidates to reach the
large gap QSH insulators with bulk direct (indirect) band gap as large as 0.4
eV (0.1 eV), and robust against external strains. The 3D crystals of these two
materials are good layered compounds with very weak inter-layer bonding and are
located near the phase boundary between weak and strong topological insulators,
which pave a new way to future experimental studies on both QSH effect and
topological phase transitions.Comment: 16 pages, 6 figure
Hamiltonian lattice quantum chromodynamics at finite density with Wilson fermions
Quantum chromodynamics (QCD) at sufficiently high density is expected to
undergo a chiral phase transition. Understanding such a transition is of
particular importance for neutron star or quark star physics. In Lagrangian
SU(3) lattice gauge theory, the standard approach breaks down at large chemical
potential , due to the complex action problem. The Hamiltonian formulation
of lattice QCD doesn't encounter such a problem. In a previous work, we
developed a Hamiltonian approach at finite chemical potential and
obtained reasonable results in the strong coupling regime. In this paper, we
extend the previous work to Wilson fermions. We study the chiral behavior and
calculate the vacuum energy, chiral condensate and quark number density, as
well as the masses of light hadrons. There is a first order chiral phase
transition at zero temperature.Comment: 23 pages. Version accepted for publication in Physical Review
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