Physics (Internal)

A Tale of Two Fluids: From the Kondo Lattice to Underdoped Cuprates

This event is part of the Physics Department Colloquia Series.

In Kondo Lattice materials, new states of matter emerge at low temperatures as a lattice of localized spins interacts with the spins carried by conduction electrons. These states include heavy electron Kondo liquids that exhibit non-Landau scaling behavior, d-wave superconductors, antiferromagnets, and quantum critical matter. Quite remarkably one encounters nearly the same states on the underdoped side of the high temperature superconductors—except that in place of a Kondo liquid that becomes superconducting at low temperatures, one finds still another kind of exotic electronic matter- pseudogap matter—out of which superconductivity grows at comparatively high temperatures. In this colloquium I review our present understanding of both classes of materials, what makes them similar, and what makes them different. I show that both contain at high temperatures two distinct fluids—a spin liquid of localized spins and a conduction electron Fermi liquid—and that in both the magnetic coupling between these localized spins sets the characteristic energy scale for their exotic normal state behavior, which differs because of the quite different magnitudes of that interaction.