The electronic structure of (Ce,Yb)CoIn5 has been studied by a combination of photoemission, x-ray absorption and bulk property measurements. Previous findings of a Ce valence near 3+ for all x and of an Yb valence near 2.3+ for x>0.3 were confirmed.
One new result of this study is that the Yb valence for x<0.2 increases rapidly with decreasing x from 2.3+ toward 3+, which correlates well with de Haas van Alphen results showing a change of Fermi surface around x=0.2. Another new result is the direct observation by angle resolved photoemission Fermi surface maps of about 50% cross sectional area reductions of the alpha- and beta-sheets for x=1 compared to x=0, and a smaller, essentially proportionate, size change of the alpha-sheet for x=0.2. These changes are found to be in good general agreement with expectations from simple electron counting. The implications of these results for the unusual robustness of superconductivity and Kondo coherence with increasing x in this alloy system are discussed.
Temperature dependent photoemission spectroscopy in Li0.9Mo6O17 contributes to evidence for one dimensional physics that is unusually robust. Three generic characteristics of the Luttinger liquid are observed, power law behavior of the k-integrated s
pectral function down to temperatures just above the superconducting transition, k-resolved lineshapes that show holon and spinon features, and quantum critical (QC) scaling in the lineshapes. Departures of the lineshapes and the scaling from expectations in the Tomonaga Luttinger model can be partially described by a phenomenological momentum broadening that is presented and discussed. The possibility that some form of 1d physics obtains even down to the superconducting transition temperature is assessed.
We report characterization results by energy dispersive x-ray analysis and AC-susceptibility for a statistically relevant number of single layer Bi-cuprate single crystals. We show that the two structurally quite different modifications of the single
-layered Bi-cuprate, namely (La,Pb=0.4)-Bi2201 and La-Bi2201, exhibit anomalies in the superconducting transition temperature at certain hole doping, e.g. at 1/8 holes per Cu. These doping values agree well with the magic doping fractions found in the temperature dependent resistance of LSCO by Komiya et al. This new set of findings suggests that all these anomalies are generic for the hole-doped high-temperature superconductors.
