Van der Waals-Zeeman Colloquium

Tue, 5 Feb 2008, 16:00h

"Dark order": what lies beneath quantum criticality?

Prof. Andy Schofield
University of Birmingham, UK

Quantum critical materials have proved to be a rich source of novel behaviour. They can be realized by, for example, tuning the transition temperature of a second order phase transition down to absolute zero with pressure or magnetic field. Then Heisenberg uncertainty rather than thermal fluctuations are responsible for melting the order. Rather than displaying an extension of the universality associated with thermal phase transitions as was expected, a growing number of examples show significant deviations from theoretical expectations (as discussed by Gegenwart). They also prove to be catalysts for generating new types of ordered state. Often this is superconductivity in metallic systems. However there are a growing number of examples of "dark order" - where the order parameter of the new phase is transparent to our current probes.