My research centers on materials that host exotic electronic states of matter at low temperatures, including superconductors, novel magnetic states, electronic glasses, topological systems, and materials in proximity to quantum critical points. My group’s general technical approach is developing techniques that use very low frequency microwave and terahertz-range radiation to probe these systems at their natural frequency scales. The material systems of interest require new measurement techniques as their relevant frequencies typically fall between the range of usual optical and electronic methods. We have developed a number of low-energy optical spectroscopies in the so-called 'terahertz gap', the experimentally difficult frequency region above that attainable with electronics, but below that accessible with optics, which is host to many important phenomena.
I am developing a new time-domain terahertz spectrometer in quasi-dc pulsed magnetic fields of up to 35 tesla. We expect the combination of large fields and fast terahertz sampling to provide a wealth of information on systems of great current interest, including quantum spin liquids, magnetic-field-induced phases of matter, and the pseudogap phase of cuprate superconductors. Another important research thrust in our group is the development of nonlinear terahertz spectroscopies. Nonlinear spectroscopic response can provide unique information about quantum correlations that are completely inaccessible in conventional linear spectroscopies. The new nonlinear spectroscopic methods will provide new information about excitations in systems as diverse as the strange metal state of cuprate superconductors, electronic glasses, and emergent fractionalized particles in spin liquids.
Emergent Phenomena in Quantum Systems
Johns Hopkins University, Department of Physics and Astronomy