Abstract
The field and spin dependence of the quasi-particle mass enhancements are examined in the paramagnetic and ferromagnetic states close to a quantum critical point. The down-spin quasi-particles are found to have heavier masses than the up-spin quasi-particles. It is also found that the spin dependence of the quasi-particles. It is also found that the spin dependence of the quasi-particle mass enhancements is through a factor of the inverse (spin dependent) Fermi wave vector. The mass enhancements drop to the spin independent value of unity at sufficiently high fields, where the magnetization starts to saturate and spin-flip scattering is suppressed. The results are compared with experimental results on CeB6.
Acknowledgements
The author would like to acknowledge useful discussions with J.M. Lawrence and J. Spalek. The author would also like to thank N. Harrison for bringing references one through three to his attention. This work was supported by a grant from the US Department of Energy, Office of Basic Energy Sciences. The manuscript is dedicated to the memory of Prof. J.E. Crow.