John Chalker






Past year

Since 1993

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Overview of Research Interests

My research is in theoretical condensed matter physics. Condensed matter physics involves using well-established physical laws - mainly quantum mechanics, electromagnetism and statistical mechanics - to understand the behaviour of solids and fluids under the range of conditions that can be produced in the laboratory - for example, by varying temperature, pressure or magnetic field strength. It is a branch of physics in which there is a rich variety of phenomena. And although the underlying laws are known, the route from them to an understanding of nature can be very subtle.

More specifically, two separate areas that I am particularly involved in at present are geometrically frustrated magnets and quantum systems far from equilibrium. Two other subjects on which I have worked extensively are the quantum Hall effect and disordered conductors.

Magnets with frustration are ones in which the microscopic interactions compete with each other, and in geometrically frustrated magnets this competition arises as a consequence of lattice structure. These systems are interesting because they behave very differently from ordinary, unfrustrated magnets. In particular, whereas conventional magnets reach an ordered state as temperature is reduced, frustrated magnets continue to fluctuate strongly even at low temperature. The theoretical and experimental effort in the area aims at understanding this fluctuating but highly correlated low temperature state.

Experiments that probe the behaviour of quantum systems far from equilibrium are currently developing rapidly in several separate fields of physics, ranging from cold atoms, through ultra-fast optics, to mesoscopic conductors. In some cases these experiments reach regimes for which there is not so far a good theoretical description. In others cases which we thought were well-understood, experiments have produced real surprises.

Some of my earlier research contributions include: work on Anderson localisation and the integer quantum Hall effect, in particular the formulation of the network model for the plateau transition; work on stripe and bubble phases in high Landau levels; identification of the chiral metal in multilayer quantum Hall systems; and studies of the Heisenberg model on the kagome and pyrochlore lattices.