Thermopower data analysis for the mercury-based HTS: Band structure calculations within a narrow-band model

摘要

We have performed the analysis of the normal-state thermopower for HgBa2Can-1CunO2n+2+delta (n=1,2,3) within a narrow-band model. This model was earlier shown to allow one to describe the normal-state transport properties for Y- and Bi-based HTS giving a possibility to determine the main band spectrum parameters (the band filling degree, the effective bandwidth and the degree of charge carrier localization) for samples of different composition. Here we apply the same approach to the Hg-based HTS with varying number of CuO2 layers for the case of the optimal doping, as well as in the underdoped and overdoped regimes. The results obtained have shown that a narrow-band model is applicable to the Hg-compounds. Our calculations show that in all the HgBa2Can-1CunO2n+2+delta phases the band filling is close to 0.5 and the conduction band is slightly asymmetrical. The total effective bandwidth for optimally doped HgBa2Can-1CunO2n+2+delta (n=1,2,3) is about 70-200 meV with a tendency to a band broadening with increasing n. We assume that this is related to forming by CuO2 layers additional states near the Fermi level that results in a rising density-of-state peak. [References: 17]