1,172 research outputs found

    Relativistic Heavy Quark Effective Action

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    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 mm is on the order of, or larger than, the inverse lattice spacing: m1/am \ge 1/a. We carry out an expansion through first order in pa|\vec p| a (where p\vec p is the heavy quark momentum) and all orders in mama, refining the analysis of the Fermilab and Tsukuba groups. We demonstrate that the spectrum of heavy quark bound states can be determined accurately through pa|\vec p| a and (ma)n(ma)^n for arbitrary exponent nn by using a lattice action containing only three unknown coefficients: m0m_0, ζ\zeta and cPc_P (a generalization of cSWc_{SW}), which are functions of mama. 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

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    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

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    We have studied a single vortex with the staggered flux (SF) core based on the SU(2) slave-boson theory of high TcT_c 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 χ\chi and pairing amplitude Δ\Delta 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

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    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

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    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

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    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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