Site web ESPCI
Jeudi 13 Avril 2017 à 14h00
Amphi Holweck, Esc C
1ème etage
Bad metals from density waves
In many bad metals the Drude peak moves away from zero frequency as the resistivity becomes large at increasing temperatures. Bad metals likely have no long-lived quasiparticles and thus rapid local equilibration leads to hydrodynamic regimes. Within hydrodynamics a Drude peak is broadened by momentum relaxation, but can only move away from zero frequency if translations are spontaneously broken. We suggest that the hydrodynamics of fluctuating, incommensurate density wave states is therefore the correct kinematic framework for discussing these materials. We show that the resistivity of such states is determined by universal diffusive processes that are independent of the rate of momentum relaxation and strength of pinning of the density wave due to e.g. weak disorder. Even weakly disordered density wave states can have large, finite resistivities, leading to bad metal behavior. We catalogue the position and width of the peak in the observed optical conductivity of many families of bad metals and show that in many cases they are k_B T/hbar. The optical and dc conductivity data of these materials, including the T-linear dc resistivity, can be understood as arising from short range quantum critical fluctuations of density wave order. Our analysis focusses on fluctuating charge density waves, but the conclusions are likely more general.