Piers Coleman
Center for Materials Theory,
Rutgers University.

QUANTUM CRITICALITY: SIGNS OF A NEW UNIVERSALITY

In the sixties and seventies, the theoretical community was profoundly shaken by the discovery of universality in statistical mechanics- a realization that the critical physics of water, magnetism and superfluidity could all be linked within a single conceptual framework. The ramifications of this revolution have since been felt far and wide throughout physics.

In this talk I shall describe how the ideas of classical criticality are being transformed into the domain of the quantum. Quantum criticality influences broad regions of the material phase diagram at finite temperatures. During the last half decade it has become possible to fine tune metals to quantum criticality- a zero temperature phase transition where critical fluctuations of the order parameter develop in both space and time. Experimentally, the properties of the metallic state at the quantum critical point appear to be described by a new class of universality for which we do not yet possess a mean-field theory. I shall describe the experiments that lead us to this conclusion and some of the radical new ideas that are circulating concerning its resolution.