Theory for non-Fermi liquid temperature dependence in resistivity of Ce_xLa_1-xCu_5.62Au_0.38 (x=0.02-0.10) on the local quantum valence criticality of Ce impurities

It was reported by Shiino et al in J. Phys. Soc. Jpn. 86, 123705 (2017) that Ce_xLa_1−xCu_5.62Au_0.38 (x = 0.02 − 0.10) exhibits a new type of quantum criticality in both magnetic and thermal properties, which is the same as that observed in a series of materials exhibiting quantum critical valence fluctuations (QCVF), such as β-YbAlB₄, Yb₁₅Al₃₄Au₅₁, and so on. However, the temperature (T) dependence in the resistivity ρ(T) for T < 0.5 K is quite anomalous, i.e., ρ(T) ∝ (const. −Tⁿ) with n ≃ 0.75 at x = 0.05. We find that this anomalous exponent is given by n = 2(1−ζ), with ζ being the weakly temperature dependent (0.5 ≲ ζ ≲ 0.7) critical exponent for the QCVF. The observed critical exponent n ≃ 0.75 at x = 0.05 is reproduced by choosing ζ ≃ 0.63 which is consistent with the divergent behavior observed in the uniform magnetic susceptibility χ ∝ T^−ζ with ζ ≃ 0.67 at x = 0.02. (author)