“Charge Fluctuations and Competing Orders in Strongly Correlated Materials”

Dragana Popovic, National High Magnetic Field Laboratory, Florida State University
PSB 160/161, 4:00-5:00pm
Friday, November 18th, 2016

Many unusual properties of strongly correlated materials have been attributed to the proximity of zero-temperature phase transitions, also known as quantum critical points (QCPs), where different types of orders compete and coexist, and may even give rise to novel phases. The role of collective fluctuations near QCPs is thus increasingly recognized as one of the key questions in the physics of strongly correlated systems. Indeed, far-from-equilibrium (or glassy) dynamics may very well be the smoking-gun manifestation of the emergent complex phenomena exhibited by these systems. Although fluctuations of various charge-ordered states have been of particular interest, e.g. to clarify their relationship with high-temperature superconductivity in cuprates, there have been relatively few studies of charge, as opposed to spin, dynamics.

This talk will describe experimental protocols, which are based on time-resolved charge transport measurements on very long time scales (hours), designed for detecting the collective behavior of electrons and probing the nature of ground states. These techniques have been applied to QCPs, such as the 2D metal-insulator transition in semiconductor heterostructures and doping-driven superconductor-insulator transition in La-based cuprates. In both systems, the results provide evidence for the charge glass nature of the insulating state and the competition of the charge glass order with the conducting phase, suggesting that glassy freezing of electrons may be a general feature of strongly correlated electronic systems near conductor-insulator transitions. Likewise, nonequilibrium charge transport protocols have recently proved to be powerful probes of the long-sought collective dynamics of charge-density-wave domains that compete with superconductivity in underdoped cuprates, paving the way to similar studies in other correlated materials.