10-year-old Physics puzzle solved
28 September 2020
Three Oxford physicists have finally solved puzzles unearthed by one of the trio ten years ago.
Working alongside his Hertford supervisor, Prof. Siddharth Parameswaran, DPhil student Michele Fava led the research that appears in a new paper published in the Proceedings of the National Academy of Sciences. The research was inspired by an unsolved puzzle proposed by Prof. Radu Coldea in a 2010 Science paper titled ‘Quantum criticality in an Ising chain: experimental evidence for emergent E8 symmetry’.
Prof. Coldea documented a spectacular series of neutron scattering measurements of Cobalt Niobate, a three-dimensional crystal where the magnetic ions form many one-dimensional chains described by the Ising model (see below). The original paper highlighted two anomalies which, despite attempts by various groups to reconcile them with the accepted model, remained unexplained.
Fava decided to revisit the original symmetry model tapping into Prof. Coldea’s expertise and identified a subtlety missed by previous theoretical models proposed for this material: the ‘real’ symmetry of the model was not just linked to the spins, but also to the way in which they were spatially arranged in a zigzag pattern along the chain. With this new insight, the trio were able to build microscopic models that allowed for these zigzag arrangements. Closely related to a particular area of expertise of Parameswaran’s, the new model provided just the insight required to change the picture.
“There is an enormous sense of satisfaction in solving these particular scientific puzzles,” explains Fava. “It is a privilege to be able to build on the work of colleagues and our microscopic model will serve others in their work on domain wall dynamics and quasiparticle decay.”
Read more, dig into the physics, and discover what an Ising model is over on the Department of Physics website.