Fermionic Critical Fluctuations: Potential Driver of Strange Metallicity and Violation of the Wiedemann–Franz Law in YbRh₂Si₂

Abstract

Results of combined thermal and electrical transport measurements through the magnetic field-induced quantum critical point in the heavy-fermion compound YbRh2Si2 are revisited to explore the relationship between the strange-metal behavior, observed in both the electrical and electronic thermal resistivity, and the violation of the Wiedemann-Franz law in the zero-temperature limit. A new type of inelastic scattering center for the charge and heat carriers has been detected and ascribed to the small-to-large Fermi-surface fluctuations, operating in the vicinity of the Kondo-destroying quantum critical point. These fermionic quantum critical fluctuations are considered the most likely driver of the strange-metal behavior and the violation of the Wiedemann-Franz law.