Speaker: Damien Stricker, Universite de Geneve
Time: February 4, 2016, 2:00 - 3:00
A reference point for research on a wider range of correlated behaviour is provided by the so-called Fermi liquids, characterized by a relaxation rate (ħω)2 + (pπkBT)2. The theoretical prediction for the relaxation rate appearing in the optical conductivity is p = 2 when considering the experimentally most accessible range ħω>kBT. A number of recent optical studies have addressed the issue of Fermi-liquid characteristics, reporting indeed ω2 and T2 for the optical scattering rate of a number of different materials. However, a perfect match to the prediction p = 2 has not been observed. One possible scenario that has been proposed to explain this discrepancy is the presence of magnetic impurities. In a recent study1 we have investigated Sr2RuO4, a material which can be synthesized in very pure form, with well established T2 resistivity below 25 K. Here we observe a perfect scaling collapse of 1/τ as a function of (ħω)2 + (pπkBT)2 for ħω < 36 meV, and temperature below 40 K, with p = 2. We also observe features in the spectrum at higher energy, which are manifestly beyond the Fermi-liquid model. The sign and size of these features agree quantitatively with the notion of resilient quasiparticles predicted by dynamical mean-field theoretical calculations for this compound. The study is extended by new high-quality transport measurement, fitted trough a simple Fermi-liquid model. The results point out that at high temperature, the model requires additional components, opening an interesting comparison with the cuprates. An insight in new data for the underdoped HgBa2CuO4+x family will be presented.