Speaker
J. Steven Dodge
(Simon Fraser University)
Description
Fermi liquid theory predicts that electron-electron scattering will contribute $\rho_{e-e}(\omega,T)=A \left[(\hbar\omega)^2+b(\pi k_B T)^2 \right]$ to the frequency-dependent resistivity of any metal at low temperatures and frequencies. In its simplest form, the theory further predicts that the temperature and frequency dependence are related by $b=4$, but numerous experimental studies have yielded $b\approx 1$ for different metals, and none have observed the predicted value. I will review progress in understanding this issue, with an emphasis on our measurements on MnSi with terahertz time-domain spectroscopy. As with other metals, the resistivity exhibits the quadratic frequency dependence predicted by Fermi liquid theory, but with $b\approx 1$ over a wide range in temperature. At the lowest temperatures, we observe evidence for a crossover to $b\approx 4$, although this is currently limited by a large systematic uncertainty that we will discuss. Additionally, we have determined the Drude scattering rate and plasma frequency at low temperatures, and compared these to realistic band theory calculations. Above a coherence temperature $T_{coh}\approx 50$ K, we find evidence for the existence of a pseudogap. Below $T_{coh}$, $\tau$ increases dramatically to $\tau\approx 0.5$~ps at $T\approx 5$~K. From a comparison of the low-temperature plasma frequency measurement with band theory, we determine a mass renormalization of $m^*/m \approx 5.5$, which compares favorably with earlier quantum oscillation measurements.
Primary author
J. Steven Dodge
(Simon Fraser University)
