My work centers on understanding how cooperative phenomena and new symmetric fields emerge out of a heterogeneous landscape, and how we can harness light to design new topological states and new phases in quantum materials.
We use a variety of complementary spectroscopies, including angle-resolved photoemission spectroscopy (ARPES), spin-resolved ARPES, time-resolved ARPES, and optical spectroscopy with mid-infrared pumping capabilities. We have also recently pioneered the application of artificial intelligence to photoemission spectroscopy, the first machine-learning-driven ARPES data acquisition, analysis and errors bootstrap.
Over the past century, the classification of states of matter has relied on the notions of symmetry, crystalline order and, more recently, topology, where crystalline order has been regarded as the holy grail for engineering enhanced materials properties. In reality, not only do all materials have some degree of disorder, but some of the most surprising and inexplicable phenomena observed in materials emerge from disordered states and do not have a counterpart in fully ordered materials. For example, mechanical properties of solids can be improved by inhibiting crystallinity, the transition temperature of an amorphous superconductor can be higher than that of a crystalline one, and most of the quantum phase transitions appear to emerge out of heterogeneous systems. It is therefore becoming clear that, to harness the power of quantum materials for the technologies of the future, we need a leap in our understanding of disorder and how electronic heterogeneity shapes materials’ behaviors and controls quantum phase transitions.
As it is often the case, new discoveries and knowledge require pushing the frontier of experimental probes. A major research thrust in my group is the development of new instrumentation for combined photoelectron spectroscopy and imaging that will be able to simultaneously probe real- and momentum-space self-organization of electronic heterogeneity in quantum materials, at the appropriate time scales. This novel experimental approach will provide a new understanding of quantum materials and disorder and may open a route to unprecedented applications of these materials, emerging from our ability to harness disorder predictably and repeatably.
Emergent Phenomena in Quantum Systems
University of California, Berkeley Department of Physics