The Hooley group

Quantum mechanics is now over a century old, and has replaced Newton's and Einstein's laws (so-called 'classical physics') as our basic description of matter.  Despite the venerable age of the quantum theory, we are still finding out new and fundamental things about the physics of quantum systems, especially those made of many particles.  These new discoveries cover both the field of equilibrium physics (what states can we expect the system to adopt if we connect it to a heat bath and wait for a long time?) and non-equilibrium physics (how does the system relax towards equilibrium, or what steady states does it reach instead if we prevent it from getting to equilibrium by continuously driving it?).

One reason for our ongoing discovery of new quantum phenomena, both in experiment and in calculations, is that the range of states available to a quantum system is much larger than that available to a classical system, because of the phenomenon of entanglement.  This makes it impossible to catalogue systematically all of the possible behaviours, at least once the number of particles gets above a few dozen, and so we need to develop reliable approximation schemes to try and deal with larger systems without missing anything important.

My group works on the theory of physical systems where these entanglement effects are unusually strong.  Examples include electrons in low-temperature metals that are about to undergo a phase change (e.g. from a paramagnet to a ferromagnet) and the magnetic moments of electrons in insulators with lattice structures that prevent simple magnetic patterns from forming (so-called 'frustrated magnets').  We also work on various interesting questions about the influence of the crystal lattice on the properties of electrons in materials, and on the interaction between quantum and gravitational effects in few-particle problems.

In the sections below you can find a bit more information about some of the current projects being pursued in the group.

PhD student Joe Crossley writes: "My research focus is on the many different methods for finding exact and approximate solutions to Hamiltonians describing interacting spins on a lattice. I've been learning lots about these tools as applied to the spin-liquid candidate Ca₁₀Cr₇O₂₈. In the process of studying this material, we've found that the currently accepted model for its magnetism doesn't reproduce the results of certain experiments very well. As a result, I'm currently studying the interactions between the magnetic Chromium atoms in this material and trying to develop an improved theory for its magnetism."