Magnets are made up of lots of quantum spins. A spin can be thought of as the quantum analogy to the simplest classical system one could imagine: a coin that shows either heads or tails. The `quantumness' of a spin manifests in properties such as
- Superposition - whilst these `quantum coins' can be heads or tails, they can also be heads and tails `at the same time'
- Entanglement - one may know everything there is to know about two spins whilst knowing essentially nothing about the state of the individual spins
- It takes two full rotations to get a spin back to its original state - after one one rotation you're only halfway there!
In terms of fundamental physics, the appeal of studying magnets is that they are the simplest systems in which all the bizzare phenomenology that makes quantum mechanics so different from everyday experience, as outlined above, plays a dominant role at the microscopic level. They therefore serve as a direct probe of emergence from a microscopic world that is as quantum mechanical as you can get, and these emergent worlds often yield many more surprises!
Perhaps my favorite example of this is the compound CoNb2O6, which undergoes a quantum phase transition where the low energy excitations at the critical point are described by the largest of the exceptional Lie groups, E8. This was detected experimentally by this research group in 2010 using neutron scattering (the experimental technique that I am focusing on in my DPhil training). As if that wasn't cool enough, the ratio of the masses of the two lowest lying excitations is exactly... you guessed it... the golden ratio!
My research focuses on experimental studies of frustrated magnets, where geometry prevents all pairwise interactions between spins from being satisfied (think of trying to place oppositely aligned spins on a triangle). I am particularly motivated to understand topological phases of matter in these systems, which could one day play a significant technological role in the quest to build error-resistant quantum computers.