Luttinger liquid behaviour of Li0.9Mo6O17 studied by scanning tunnelling microscopy
Scanning tunnelling spectroscopy (STS) was used to study the Luttinger liquid behaviour of the purple bronze Li0.9Mo6O17 in the temperature range 5 K < T < 300 K. In the entire temperature range the suppression of the density of states at the Fermi energy can be fitted very well by a model describing the tunnelling into a Luttinger liquid at ambient temperature. The power-law exponent extracted from these fits reveals a significant increase above 200 K. It changes from α = 0.6 at low temperature to α = 1.0 at room temperature.
Calculated Effects of Disorder on the Mo Core Levels in Purple Bronze Li2Mo12O34
The band structures of ordered and thermally disordered Li 2 Mo 12 O 34 are calculated by use of ab initio density functional theory (DFT)–Linear Muffin-Tin Method (LMTO) with a focus on the behavior of the Mo 3d -core levels. It is shown that thermal disorder and zero-point motion lead to substantial core level broadening, and the broadening at room temperature is predicted to be sufficiently larger than at zero degrees to allow for a detection by X-ray photoelectron spectroscopy (XPS) measurements. However, real purple bronze has 10% Li vacancies, and static disorder will attenuate the T-dependent broadening. It is argued that core level spectroscopies could be a useful tool for the measurement of thermal disorders in many materials, especially for those with minor static disorder. Studies of core levels in magnetic materials will be helpful for an understanding of T-dependent spin moments.
Optical spectral weight and the physics of correlated electron systems
Abstract The theory of the optical conductivity of ‘correlated electron systems’ (mainly transition metal oxides with narrow, d-derived conduction bands) is reviewed, with emphasis on effective models and on a restricted sum rule that enables the extraction of the electron kinetic energy from optical data.