My laboratory brings together unique methods that can probe and control excitations in quantum materials with high time, energy and momentum resolutions. Our battery of experimental tools includes various forms of coherent ultrafast spectroscopy, time-resolved ARPES (angle-resolved photoemission spectroscopy) and ultrafast electron diffraction. Using these techniques, we investigate topological materials, high temperature superconductors and atomically thin layered materials, seeking to understand both their equilibrium properties and their light-induced non-equilibrium states. In many of these systems, different degrees of freedom (charge, spin, lattice) are strongly coupled, and interplay between them is responsible for many of interesting physical properties.
Our time-resolved techniques can selectively probe the dynamics of charge, spin and lattice excitations and thus elucidate the microscopic mechanisms underlying these properties. My ultimate dream is to use light as a controllable tuning parameter (just as magnetic field or pressure) to switch between equilibrium phases and to engineer new light-induced states with no equilibrium counterparts.
One of our current efforts is aimed at improving the capabilities of our time-resolved ARPES apparatus to achieve experimental detection of light-induced transitions between different topological phases of matter, such as turning a trivial insulator to a topological one via photo-induced band inversion.
Another important research thrust in our group is using different optical excitation schemes to look for novel light-induced phases in correlated electron systems and to study phase competition between equilibrium phases. The primary focus will be on cuprate superconductors, which are particularly rich in various equilibrium phases that can either coexist or interchange as temperature and chemical composition are varied. Our goal is to learn to control these phases by tailoring the properties of the optical excitation.
Emergent Phenomena in Quantum Systems