Non-fermi-liquid behavior in electronic specific heat of heavy-fermion superconductor Ce2CoIn8

Ce2CoIn8 is a heavy-fermion superconductor with the transition temperature of T-c = 0.4 K. We have measured the low temperature specific heat under high magnetic fields on pure powder single crystals of Ce2CoIn8. Below 0.6 K. the electronic specific heat C-e divided by temperature T1Ce/T increases with decreasing temperature at zero field, indicating a superconducting transition. At around T-M similar to 2 K, a broad maximum appears in C-e/T and it shifts to lower temperatures with increasing field, indicating the existence of antiferromagnetic (AF) correlations. In fields, a - log T dependence in C-e/T observed above T-M develops and finally it covers the measured temperature range of 0.25 K < T < 10 K under H = 80 kOe. Therefore, this non-fermi-liquid behavior is attributable to a quantum critical point associated with the antiferromagnetic correlations. The present observation indicates that the heavy-fermion superconductivity in Ce2CoIn8 is mediated by the AF correlations. (C) 2010 Published by Elsevier B.V.