Quantum-Critical, Spin-Fluctuation-driven Residual Resistivity and Emergent Universal Correlations in the Fermi-Liquid Regime of Heavy-Fermion Superconductors
We investigate correlations within the unconventional Fermi-liquid (FL) regime of quantum-critical (QC) heavy-fermion superconductors (HFSs) by tracking the pressure dependence of three quantities: the temperature-independent, SF-driven residual resistivity, $\rho^{ sf}_{0}(P)$; the FL scattering coefficient, $A(P)$; and the superconducting transition temperature, $T_c(P)$. The first two define the spin-fluctuation contribution to the resistivity, $\rho(T)=\rho^{sf}_0+AT^2$. Using experimental data from archetypal heavy-fermion systems, we identify three robust empirical correlations: $\ln(\frac{T_c}{\theta}) \propto A^{-1/2}$, $A \propto (\rho^{sf}_0)^2$, and $\ln(\frac{T_c}{\theta}) \propto \big(\rho^{sf}_0\big)^{-1}$ ($\theta$ is a characteristic temperature scale). Absent in conventional FL superconductors, these relationships indicate that QC fluctuations not only mediate inelastic scattering and Cooper pairing, but also generate an effective elastic channel responsible for $\rho^{sf}_0$. We explicitly calculate $\rho^{sf}_0$ on the high-pressure side of the quantum critical point (QCP) and introduce a characteristic length scale, $\ell \sim \big(\rho^{sf}_0\big)^{-1}$, that captures the spatial extent of fluctuation-induced scattering. Within this regime, and within the Migdal--Eliashberg framework combined with Boltzmann transport theory, we derive analytic expressions for $T_c(\ell)$ and $A(\ell)$, together with their interrelations, which are consistent with the observed empirical trends. These findings highlight the quantum-critical FL regime in HFSs as an intrinsically correlated phase, governed by fluctuations and marked by unconventional transport and pairing mechanisms.