Quasiparticle bandwidth

Impurity scattering leads to the formation of the gapless state at some sectors zero energy, N(0), where N(0) is the 2D density of states per spin at the Fermi level, and leads to a universal quasiparticle interlayer conductivity crg(0,0) ... 

Purely with optical means also the bandwidth of the quasiparticle bands could be determined and they range for the five investigated materials between 1 meV to 15 meV These bandwidths are in full agreement with calculated bandwidths from high-resolution photoemission at low temperatures (e.g., Patthey et al. 1990) or with the quasielastic line width of inelastic neutron scattering (e.g., Goldman et al, 1987) and they are also a measure of the Kondo temperature. 

The Sri-xCaxRuOs system exhibits both a non-Drude low frequency optical conductivity, electronic Raman continuum [165-167], similar to that seen in the high T cuprates [62] (see Sect. 3.1.2). Several noteworthy features have been observed in photoemission and optical spectra of Sri-xCaxRuOs as a function of bandwidth. First, Ahn et al. observe two mid-infrared optical features below 5 eV a peak near 1.5 eV, which the authors attribute to transitions between the quasiparticle band and the upper and lower Hubbard bands ( U/2), and a peak near 3 eV, which the authors identify as the transition between upper and lower Hubbard bands, U. This interpretation of the data is consistent with the spectral features predicted in calculations of the infinite-dimensional Hubbard model [72], and also with a recent interpretation of the optical data for the Sri xCaxV03 system [71]. Strong electronic correlation effects are also apparent in photoemission... 

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