The electronic transport properties of conventional three-dimensional metals are successfully described by Fermi-liquid theory. But when the dimensionality of such a system is reduced to one, the Fermi-liquid state becomes unstable to Coulomb interactions, and the conduction electrons should instead behave according to Tomonaga-Luttinger-liquid (TLL) theory. Such a state reveals itself through interaction-dependent anomalous exponents in the correlation functions, density of states and momentum distribution of the electrons. Metallic single-walled carbon nanotubes (SWNTs) are considered to be ideal one-dimensional systems for realizing TLL states. Indeed, the results of transport measurements on metal-SWNT and SWNT-SWNT junctions have been attributed to the effects of tunnelling into or between TLLs, although there remains some ambiguity in these interpretations. Direct observations of the electronic states in SWNTs are therefore needed to resolve these uncertainties. Here we report angle-integrated photoemission measurements of SWNTs. Our results reveal an oscillation in the pi-electron density of states owing to one-dimensional van Hove singularities, confirming the one-dimensional nature of the valence band. The spectral function and intensities at the Fermi level both exhibit power-law behaviour (with almost identical exponents) in good agreement with theoretical predictions for the TLL state in SWNTs.

We have performed a high-resolution angle resolved Ce 4d-4f resonant photoemission experiment on the heavy fermion superconductor CeIrIn 5 . We have observed a quasi-particle band which has an energy dispersion of 30 meV in the Ce 4f on-resonance spectra. The result suggests that although the 4f spectra are dominated by the localized/correlated character, the small itinerant component is responsible for the superconductivity in this compound. 71.27.+a, 71.18.+y I.

In order to study the electronic states of solids, using high-resolution, low-temperature photoemission spectroscopy (PES) with tunable photon energies, we have constructed a high-resolution undulator beamline operating in the photon-energy range 26–300 eV at the compact 700 MeV electron-storage ring HiSOR located at Hiroshima University. By way of gas-phase experiments, with photon flux larger than 2 × 1010 photons/s, photon-energy resolving powers of E/ΔE > 16000 and 3800 were obtained at hν ~ 48 eV and ~ 244 eV, respectively. High-resolution PES experiments on evaporated Au at 8 K were performed at the beamline with a total energy resolution of ΔE = 12 meV at hν = 48 eV. Among the first experiments from the beamline, a resonant photoemission study of UNiSn is presented. The U 5f derived peak is significantly enhanced at hν = 98 eV.

Ce 4 f derived states at the Fermi level (E F ) of the isostructural single crystals CeRhAs, CeRhSb, and CePtSn were observed directly by means of high-resolution (⌬Eϭ18-20 meV), low-temperature ͑10-12 K͒ photoemission spectroscopy with a photon energy of hϭ126 eV. The Ce 4 f spectrum for the Kondo semiconductor CeRhAs exhibited no peak structure near E F , and its spectral intensity decreases monotonically above the binding energy ϳ90 meV, thereby forming a large gap structure. The spectrum of the semimetal CeRhSb is enhanced above ϳ120 meV, but decreases steeply above ϳ13 meV, which indicates the existence of a narrow pseudogap at E F . A clear crystal field excitation at ϳ27 meV, and a weak Kondo resonance at E F , were found in the metal CePtSn.

No abstract