16,004 research outputs found
Correlation strength, gaps, and particle-hole asymmetry in high-T-c cuprates: A dynamical mean field study of the three-band copper-oxide model
No full textThe three-band model relevant to high-temperature copper-oxide superconductors is solved using single-site dynamical mean field theory and a tight-binding parametrization of the copper and oxygen bands. For a band filling of one hole per unit cell the metal/charge-transfer-insulator phase diagram is determined. The electron spectral function, optical conductivity, and quasiparticle mass enhancement are computed as functions of electron and hole doping for parameters such that at one hole per cell the paramagnetic phase is insulating and for parameters such that at one hole per unit cell the paramagnetic phase is metallic. The optical conductivity is computed using the Peierls phase approximation for the optical matrix elements. The calculation includes the physics of "Zhang-Rice singlets." The effects of antiferromagnetism on the magnitude of the gap and the relation between correlation strength and doping-induced changes in state density are determined. Three-band and one-band models are compared. The two models are found to yield quantitatively consistent results for all energies less than about 4 eV including energies in the vicinity of the charge-transfer gap. Parameters on the insulating side of the metal/charge-transfer insulator phase boundary lead to gaps which are too large and near-gap conductivities which are too small relative to data. The results place the cuprates clearly in the intermediate correlation regime, on the paramagnetic metal side of the metal/charge-transfer insulator phase boundary. RI Capone, Massimo/A-7762-2008; Wang, Xin/F-5509-2011; de' Medici, Luca/H-5071-201
Antiferromagnetism and the gap of a Mott insulator: Results from analytic continuation of the self-energy
No full textDirect analytic continuation of the self-energy is used to determine the effect of antiferromagnetic ordering on the spectral function and optical conductivity of a Mott insulator. Comparison of several methods shows that the most robust estimation of the gap value is obtained by use of the real part of the continued self-energy in the quasiparticle equation within the single-site dynamical mean-field theory of the two-dimensional square lattice Hubbard model, where, for a U that is slightly greater than the Mott critical value, antiferromagnetism increases the gap by about 80%. RI Capone, Massimo/A-7762-2008; Wang, Xin/F-5509-2011; de' Medici, Luca/H-5071-2011; Gull, Emanuel/A-2362-201
On the AJ Conjecture for Knots
No full textWe confirm the AJ conjecture [Ga2] that relates the A-polynomial and the colored Jones polynomial for hyperbolic knots satisfying certain conditions. In particular, we show that the conjecture holds true for some classes of two-bridge knots and pretzel knots. This extends the result of the first author in [Le2], who established the AJ conjecture for a large class of two-bridge knots, including all twist knots. Along the way, we explicitly calculate the universal SL₂(C)-character ring of the knot group of the (−2, 3, 2n + 1)-pretzel knot, and show it is reduced for all integers n
Mechanism of microtubule stabilization by taccalonolide AJ
No full textInternational audienceAs a major component of the cytoskeleton, microtubules consist of αβ-tubulin heterodimers and have been recognized as attractive targets for cancer chemotherapy. Microtubule-stabilizing agents (MSAs) promote polymerization of tubulin and stabilize the polymer, preventing depolymerization. The molecular mechanisms by which MSAs stabilize microtubules remain elusive. Here we report a 2.05 Å crystal structure of tubulin complexed with taccalonolide AJ, a newly identified taxane-site MSA. Taccalonolide AJ covalently binds to β-tubulin D226. On AJ binding, the M-loop undergoes a conformational shift to facilitate tubulin polymerization. In this tubulin–AJ complex, the E-site of tubulin is occupied by GTP rather than GDP. Biochemical analyses confirm that AJ inhibits the hydrolysis of the E-site GTP. Thus, we propose that the β-tubulin E-site is locked into a GTP-preferred status by AJ binding. Our results provide experimental evidence for the connection between MSA binding and tubulin nucleotide state, and will help design new MSAs to overcome taxane resistance
Functional consortium for hydrogen production from cellobiose: Concentration-to-extinction approach
No full textL6-X6 intervalley scattering time and deformation potential for Al0.6Ga0.4As determined by femtosecond time-resolved infrared absorption spectroscopy
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Tropospheric ozone climatology over Beijing : analysis of aircraft data from the MOZAIC program
No full textAuthor name used in this publication: Wang, T.2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedC
Determination of the critical value of xc for the direct-to-indirect band-gap transition in AlxGa1-xAs by measuring hot-carrier dynamics in the X valley
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