Volume 80, Number 3, November 2007
Article Number 37005
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 28 September 2007
EPL, 80 (2007) 37005
DOI: 10.1209/0295-5075/80/37005

The Lorenz number in CeCoIn5 inferred from the thermal and charge Hall currents

Y. Onose1, N. P. Ong1 and C. Petrovic2

1  Department of Physics, Princeton University - Princeton, NJ 08544, USA
2  Department of Physics, Brookhaven National Laboratory - Upton, NY 11973, USA

received 25 June 2007; accepted in final form 5 September 2007; published November 2007
published online 28 September 2007

The thermal Hall conductivity $\kappa _{xy}$ and Hall conductivity $\sigma _{xy}$ in CeCoIn5 are used to determine the Lorenz number ${\cal L}_H $ at low temperature T. This enables the separation of the observed thermal conductivity into its electronic and non-electronic parts. We uncover evidence for a charge-neutral, field-dependent thermal conductivity, which we identify with spin excitations. At low T, these excitations dominate the scattering of charge carriers. We show that suppression of the spin excitations in high fields leads to a steep enhancement of the electron mean-free-path, which leads to an interesting scaling relation between the magnetoresistance, thermal conductivity and $\sigma _{xy}$.

71.27.+a - Strongly correlated electron systems; heavy fermions.
72.15.Eb - Electrical and thermal conduction in crystalline metals and alloys.
72.20.My - Galvanomagnetic and other magnetotransport effects.

© Europhysics Letters Association 2007