Terahertz Conductivity Measurements of MnSi

This thesis presents measurements of the dynamical conductivity of a MnSi lm via terahertz time domain spectroscopy. We determine the Drude scattering rate and plasma frequency at low temperatures, and compare these to theoretical predictions. From a comparison of the plasma frequency measurement with band theory, we determine a mass renormalization of m*/m~5.5. Above the critical temperature, ts to the Drude model yield negative values for the scattering lifetime, indicating the existence of a pseudogap. At low temperatures and low frequencies, the resistivity has the well-known Fermi liquid form with the ratio of the temperature dependent term to the frequency dependent term, b>1. At the lowest temperature we estimate b ~ 4, with a large systematic uncertainty that we characterize for later improvement. This result is consistent with Fermi liquid theory predictions for electron-electron scattering.