Volume 88, Number 4, November 2009
Article Number 47005
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 03 December 2009
EPL, 88 (2009) 47005
DOI: 10.1209/0295-5075/88/47005

Enhancement of the Hall-Lorenz number in optimally doped YBa2Cu3O7-d

M. Matusiak1, K. Rogacki1 and B. W. Veal2

1   Institute of Low Temperature and Structure Research, Polish Academy of Sciences - P.O. Box 1410, 50-950 Wrocław, Poland, EU
2   Materials Science Division, Argonne National Laboratory - Argonne, IL 60439, USA

received 27 August 2009; accepted in final form 3 November 2009; published November 2009
published online 3 December 2009

Electronic heat transport in the normal state of a high-quality single crystal of the optimally doped superconductor YBa2Cu3O6.95 was studied by measurements of longitudinal and transverse transport coefficients. For the temperature range from 100 to 300 K, the Hall-Lorenz number (Lxy) depends weakly on temperature and is about two times larger than the Sommerfeld value of the Lorenz number L0 = $\pi ^{2}$/3. Our results can be interpreted using a Fermi liquid model when effects of the pseudogap that opens at the Fermi level are included. However, we find that the bipolaron model can also explain both the enhanced value and the weak temperature dependence of the Hall-Lorenz number.

74.25.Fy - Transport properties (electric and thermal conductivity, thermoelectric effects, etc.).
74.72.Bk - Y-based cuprates.

© EPLA 2009