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Strong Correlation between Anomalous Quasiparticle Scattering and Unconventional Superconductivity in Hidden Order Phase of URu$_2$Si$_2$

The pressure dependent electrical resistivity of URu$_2$Si$_2$ has been studied at high pressure across the first order phase boundary of $P_x$ where the ground state switches under pressure from "hidden order" (HO) to large moment antiferromagnetic (LAFM) states. The electrical transport in URu$_2$Si$_2$ at low temperatures shows a strong sample dependence. We have measured an ultra-clean single crystal whose quality is the highest among those used in previous studies. The generalized power law $ρ{\,}={\,}{ρ_0}+{\,}{A_n}T{^n}$ analysis finds that the electric transport property deviates from Fermi liquid theory in the HO phase but obeys the theory well above $P_x$. The analysis using the polynomial in $T$ expression $ρ{\,}={\,}{ρ_0}+{\,}{α_1}T+{\,}{α_2}T{^2}$ reveals the relation ${α_1}/{α_2}$ $\propto$ $T_{sc}$ in the HO phase. While the pressure dependence of ${α_2}$ is very weak, ${α_1}$ is roughly proportional to $T_{sc}$. This suggests a strong correlation between the anomalous quasiparticle scattering and the superconductivity and that both have a common origin. The present study clarifies a universality of the HO phase inherent in strongly correlated electron superconductors near quantum criticality.