1,097 research outputs found
Relativistic Heavy Quark Effective Action
We study the fermion action needed to accurately describe the low energy
physics of systems including heavy quarks in lattice QCD even when the heavy
fermion mass is on the order of, or larger than, the inverse lattice
spacing: . We carry out an expansion through first order in (where is the heavy quark momentum) and all orders in ,
refining the analysis of the Fermilab and Tsukuba groups. We demonstrate that
the spectrum of heavy quark bound states can be determined accurately through
and for arbitrary exponent by using a lattice action
containing only three unknown coefficients: , and (a
generalization of ), which are functions of . In a companion paper,
we show how these three coefficients can be precisely determined using
non-perturbative techniques.Comment: 40 pages, 1 figur
Phenomenology of Photoemission Lineshapes of High Tc Superconductors
We introduce a simple phenomenological form for the self-energy which allows
us to extract important information from angle resolved photoemission data on
the high Tc superconductor Bi2212. First, we find a rapid suppression of the
single particle scattering rate below Tc for all doping levels. Second, we find
that in the overdoped materials the gap Delta at all k-points on the Fermi
surface has significant temperature dependence and vanishes near Tc. In
contrast, in the underdoped samples such behavior is found only at k-points
close to the diagonal. Near (pi,0), Delta is essentially T-independent in the
underdoped samples. The filling-in of the pseudogap with increasing T is
described by a broadening proportional to T-Tc, which is naturally explained by
pairing correlations above Tc.Comment: 4 pages, revtex, 3 encapsulated postscript figure
Staggered local density-of-states around the vortex in underdoped cuprates
We have studied a single vortex with the staggered flux (SF) core based on
the SU(2) slave-boson theory of high superconductors. We find that
whereas the center in the vortex core is a SF state, as one moves away from the
core center, a correlated staggered modulation of the hopping amplitude
and pairing amplitude becomes predominant. We predict that in this
region, the local density-of-states (LDOS) exhibits staggered modulation when
measured on the bonds, which may be directly detected by STM experiments.Comment: 4 pages, 3 figure
Thermal and magnetic properties of spin-1 magnetic chain compounds with large single-ion and in-plane anisotropies
The thermal and magnetic properties of spin-1 magnetic chain compounds with
large single-ion and in-plane anisotropies are investigated via the integrable
su(3) model in terms of the quantum transfer matrix method and the recently
developed high temperature expansion method for exactly solved models. It is
shown that large single-ion anisotropy may result in a singlet gapped phase in
the spin-1 chain which is significantly different from the standard Haldane
phase. A large in-plane anisotropy may destroy the gapped phase. On the other
hand, in the vicinity of the critical point a weak in-plane anisotropy leads to
a different phase transition than the Pokrovsky-Talapov transition. The
magnetic susceptibility, specific heat and magnetization evaluated from the
free energy are in excellent agreement with the experimental data for the
compounds NiC_2H_8N_2)_2Ni(CN)_4 and Ni(C_{10}H_8N_2)_2Ni(CN)_4.H_2O.Comment: 18 pages, 6 figures, to appear in PR
Electronic structure of kinetic energy driven superconductors
Within the framework of the kinetic energy driven superconductivity, we study
the electronic structure of cuprate superconductors. It is shown that the
spectral weight of the electron spectrum in the antinodal point of the
Brillouin zone decreases as the temperature is increased. With increasing the
doping concentration, this spectral weigh increases, while the position of the
sharp superconducting quasiparticle peak moves to the Fermi energy. In analogy
to the normal-state case, the superconducting quasiparticles around the
antinodal point disperse very weakly with momentum. Our results also show that
the striking behavior of the superconducting coherence of the quasiparticle
peaks is intriguingly related to the strong coupling between the
superconducting quasiparticles and collective magnetic excitations.Comment: 8 pages, 4 figures, added discussions and updated references,
accepted for publication in Physics Letters
5,5′-Bis[(2,2,2-trifluoroethoxy)methyl]-2,2′-bipyridine
The complete molecule of the title compound, C16H14F6N2O2, is generated by crystallographic inversion symmetry, which results in two short intramolecular C—H⋯N hydrogen-bond contacts per molecule. In the crystal, aromatic π–π stacking [centroid–centroid distance = 3.457 (2) Å] and weak C—H⋯π interactions occur. A short H⋯H [2.32 (3) Å] contact is present
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