Colloquium on February 13, 2012

Andrew G. Green
London Centre of Nanotechnology, University College London

New Horizons in Quantum Criticality

Two of the central aims of theoretical physics are to understand strongly correlated quantum behaviour and the behaviour of quantum systems when driven out of equilibrium. These present us with some of our most profound scientific questions. Addressing them requires novel ideas and techniques, and can reveal some surprising links.

I will discuss a particular type of strongly correlated quantum systems known as quantum critical. Electronic quantum critical systems are particularly susceptible to the formation of new phases. I will describe a simple picture of this phase reconstruction and how it can be related to certain instabilities of black holes through a mathematical mapping known as holography.

It turns out that the strong quantum correlations present in quantum critical systems in thermal equilibrium constrain their out-of-equilibrium behaviour in a way that leads to new universality. I will show how this might be revealed in measurements of current noise. This is related through the holographic mapping to Hawking radiation from a black hole. Certain general properties of gravitational metrics suggest new universal features of the out-of-equilibrium quantum critical system.