Electronic structures of AlB 2 -type superconducting YbGa 1 + x Si 1 − x alloys probed by NMR and Seebeck coefficient

• Published in: Journal of applied physics Vol. 108; no. 7; pp. 073911 - 073911-4
• Main Authors: Fang, C. P., Lue, C. S., Hsu, Y. D., Kuo, Y. K.
• Format: Journal Article
• Published: American Institute of Physics 05.10.2010
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3488901

We report the electronic properties of the AlB 2 -type compounds YbGa 1 + x Si 1 − x ( x = 0 , 0.15, and 0.3) studied by means of the nuclear magnetic resonance (NMR) and the Seebeck coefficient measurements. These materials are of current interest due to the presence of superconductivity with Yb element. From the analysis of G 69 a NMR spin-lattice relaxation rates, we deduce the Ga   4 s partial Fermi level density of states N s ( E F ) for these compounds. The result indicates a gradual increase in N s ( E F ) with increasing x in YbGa 1 + x Si 1 − x . In addition, the evolution of the Seebeck coefficient feature can be understood well within the band-filling scenario. From the Seebeck coefficient analysis, we find that the variation in the total Fermi level density of states N ( E F ) is not consistent with the trend of superconducting temperature T c which shows a gradual decrease with Ga content. These observations support the hypothesis that the electronic Fermi level density of states is not the key factor in determining the superconducting transition temperature of YbGa 1 + x Si 1 − x .