Heavy carriers and non-Drude optical conductivity in MnSi

The optical properties of the weakly helimagnetic metal MnSi have been determined in the photon energy range from 2 meV to 4.5 eV using the combination of grazing incidence reflectance at 80^∘ (from 2 meV to 0.8 eV) and ellipsometry (from 0.8 to 4.5 eV). As the sample is cooled below 100 K, the effective mass develops a strong frequency dependence at low frequencies, while the scattering rate developes a sublinear frequency dependence. The complex optical conductivity can be described by the phenomenological relation σ(ω,T)∝[Γ(T)+iω]^-0.5.