I explore the interplay between magnetism, strong electron correlations, and electronic topology in metals, semi-metals and superconductors. The primary experimental method employed by my group is neutron scattering, which is an ideal probe of magnetism in materials. I have a long-standing involvement in development of neutron scattering instrumentation and have served on various committees overseeing instrumentation development at national facilities for neutron scattering.
Much can be learned about the fundamental properties of a magnetic material by exposing it to a pulsed magnetic or electromagnetic field and probing the time-dependent process by which the material departs from and then returns to thermal equilibrium. Until recently, the arsenal of experimental techniques that can allow such investigations has not included neutron scattering. We have developed new techniques that allow studies of non-equilibrium magnetic properties by measuring time-dependent neutron scattering response following a pulsed magnetic field or pulsed microwaves. The techniques are being implemented at the NIST Center for Neutron Research and we are currently working to achieve better time resolution and higher sensitivity.
A particularly intriguing target of investigation are quantum spin liquids, in which many billion spins in a material are quantum mechanically entangled. While at present there are many examples of candidate quantum spin liquids, there is a striking lack of experimental techniques that can yield ‘smoking-gun’ evidence of this elusive state. What is needed are techniques that can probe the many-body quantum entanglement itself — a daunting technical task.
My group is currently exploring the ways in which novel neutron scattering approaches, based on beams of entangled neutrons, can be used to develop a model-independent experimental probe of the degree and extent of quantum entanglement in solids.
Emergent Phenomena in Quantum Systems
Johns Hopkins University, Department of Physics and Astronomy