From nodal liquid to nodal Mottness in a frustrated Hubbard model

We investigate the physics of frustrated 3-leg Hubbard ladders in the band limit, when hopping across the ladder's rungs (t$_{\perp}$) is of the same order as hopping along them (t) much greater than the onsite Coulomb repulsion (U). We show that this model exhibits a striking electron-hole asymmetry close to half-filling: the hole-doped system at low temperatures develops a Resonating Valence Bond (RVB)-like d-wave gap (pseudogap close to ($\pi$,0)) coinciding with gapless nodal excitations (nodal liquid); in contrast, the electron-doped system is seen to develop a Mott gap at the nodes, whilst retaining a metallic character of its majority Fermi surface. At lower temperatures in the electron-doped case, d-wave superconducting correlations -- here, coexisting with gapped nodal excitations -- are already seen to arise. Upon further doping the hole-doped case, the RVB-like state yields to d-wave superconductivity. Such physics is reminiscent of that exhibited by the high temperature cuprate superconductors--notably electron-hole asymmetry as noted by Angle Resolved PhotoEmission Spectroscopy (ARPES) and the resistivity exponents observed. This toy model also reinforces the importance of a more thorough experimental investigation of the known 3-leg ladder cuprate systems, and may have some bearing on low dimensional organic superconductors.Comment: 26 pages, 16 figure

Metal Ion Complexes with HisGly: Comparison with PhePhe and PheGly

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Infrared Multiple-Photon Dissociation Spectroscopy of Tripositive Ions: Lanthanum-Tryptophan Complexes

Collision-induced charge disproportionation limits the stability of triply charged metal ion complexes and has thus far prevented successful acquisition of their gas-phase IR spectra. This has curtailed our understanding of the structures of triply charged metal complexes in the gas phase and in biological environments. Herein we report the first gas-phase IR spectra of triply charged La-III complexes with a derivative of tryptophan (N-acetyl tryptophan methyl ester), and an unusual dissociation product, a lanthanum amidate. These spectra are compared with those predicted using density functional theory. The best structures are those of the lowest energies that differ by details in the a-interaction between La3+ and the indole rings. Other binding sites on the tryptophan derivative are the carbonyl oxygens. In the lanthanum amidate, La3+ replaces an H+ in the amide bond of the tryptophan derivative

Alkali-Metal-Ion-Assisted Hydrogen Atom Transfer in the Homocysteine Radical

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Generation, Characterization, and Dissociation of Radical Cations Derived from Prolyl-glycyl-glycine

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Spin-relaxation in an InGaAs/InP MQW

Room temperature picosecond pump-probe transmission measurements on InGaAsP/InGaAsP MQWs have shown large rotation (~40°) of probe polarisation induced by circularly polarised pump. We report low temperature investigations in a lattice matched In0.43Ga0.57As/InP MQW 8nm wide which does not reproduce this remarkable effect. Our measurements were made with an all-solid-state optical parametric oscillator tunable from 1.2 to 6µm. The non-linear crystal is periodically poled lithium niobate fabricated at Southampton, pumped synchronously by a modelocked, diode pumped Nd:YLF laser