2019 John William Strutt, Lord Rayleigh Medal and Prize
Professor Nigel Cooper for profound contributions to the quantum theory of many-particle systems, concerning both topological phases of cold atoms in artificial gauge fields and novel phenomena in electronic materials.
Nigel Cooper is one of the leading condensed matter theorists of his generation. He has made seminal contributions both to the field of cold atomic gases and to that of electronic materials.
Cooper's engagement with the atomic physics community has been central to the development of studies of topological phenomena using cold gases. He is the author of ground-breaking works predicting novel quantum many-body phases. In particular, he predicted the behaviour of vortex phases in rotating gases of bosonic atoms, becoming the first to elucidate the relation between such systems and the quantum Hall effect, and initiating lines of research for quantum Hall theorists and for cold atom experimentalists. He exploited his deep knowledge of atomic physics to guide experiment towards the realization and characterization of topological bands for cold atoms. He proposed a new methodology to engineer artificial gauge fields that mimic the effect of magnetic fields, based on ‘optical flux lattices’. Cooper's proposals for creating topological bands using dynamic superlattices and his general method for measuring band geometry contributed directly to the successful implementations and detection of Chern bands in cold gases. Indeed, he is a co-author of the paper reporting the first measurement of the Chern number using cold atomic gases.
In the field of electronic materials, Cooper’s contributions include both important theoretical advances as well as direct explanations of experimental data. The ‘topological Kondo effect’ for Coulomb-blockaded topological superconductors, a remarkable discovery of Benjamin Béri and Cooper, provides a surprisingly simple way to demonstrate the expected non-local character of Majorana fermions in realistic experiments. Through an analysis of experimental measurements of the magnetization oscillations in a Kondo insulator, Johannes Knolle and Cooper showed that the standard theory of quantum oscillations, held for over 50 years, is incomplete: whereas quantum oscillations were assumed to provide a definitive signature of a Fermi surface, they showed that there can be quantum oscillations even for band insulators of certain types.