Research Interests

High Temperature Superconductivity

I have worked on properties of high-temperature superconductors since their discovery in 1987. In particular I have focussed on the role played by vortices in these strongly Type-II superconductors. Superconductors will only carry currents without dissipation if the field-induced vortex lines within them are not driven along by the current but are pinned instead by defects in the superconductor. For the commercial exploitation of high-temperature superconductors it is thus vital to understand the interplay between thermal fluctuations and the pinning by defects and disorder.

My current research is focussed on understanding the growth of crystalline order of the Abrikosov vortex lattice following a quench from the high-temperature state, the role of defects on the nature of the phase diagram and whether the "lower critical end-point" seen in many experiments is an intrinsic effect or a consequence of defects in the crystal.

Interface Growth

A whole variety of phenomena such as the growth of surfaces in an MBE machine, the growth of snowdrifts and the accretion of comets from lumps of ice are descibed by a generalised (non-linear) diffusion equation, the Kardar, Parisi, Zhang (KPZ) equation. This equation has attracted much interest amongst theoretical physicists not only because of its widespead utility but because it provides an example of a non-perturbative situation in which no small parameter can be identified. This is also a feature of other "difficult" problems in physics such as fully developed turbulence and QCD. However, the KPZ equation is much better understood than these other topics because of accurate numerical simulations so the hope is that if we can develop analytical tools for it then they may have applicability elsewhere. Progress has been made by developing a particular closed form approximation - the mode coupling equations - but the solution of them is a numerical challenge.

Spin Glasses

I have studied spin glasses  for many years.  They are still one of the most controversial topics in condensed matter physics. There are two rival pictures of their properties, the "droplet" picture and the "replica symmetry breaking picture". My research of the last few years has been focussed on detemining which of these two rival theories is correct.