What happens when a material is tuned so that the critical temperature for a continuous phase transition between two uniform magnetic states is driven to zero kelvin? At zero kelvin the entropy is zero and any change of state has to be brought about by quantum rather than thermal fluctuations. The point at which this occurs is known as a quantum critical point and is the source of some very interesting physics.
Theoretical work to understand the physics close to quantum critical points has been fuelled by a number of recent experimental discoveries. One of the most exciting is the discovery that completely new correlated-electron ground states form in very pure materials. In our own work we found an unusual form of superconductivity homogeneously co-existing with ferromagnetism.