Our group conducts research on “highly correlated electron systems,” now more often referred to as “quantum materials.” When we use the word “quantum” in this context, what we really mean is “edgy.” Quantum materials are never very far from a phase boundary, and can often be tipped into another phase by relatively weak external stimuli, in the form of applied currents or photoexcitation. This edginess results from a multiplicity of competing interactions, each of which favors a diffent groundstate.
The potential for the discovery of new phases, as well as the ability to controllably switch between them, accounts for the tremendous interest in quantum materials. However, their diversity and complexity requires a multidisciplinary and multi-investigator approach. Our lab is part of the Quantum Materials Team at Lawrence Berkeley Lab and the UC Berkeley Physics and Materials Science Departments. The other principal co-investigators are Profs. Lanzara, Lee, Ramesh, and Vishwanath.
In the Orenstein group we develop and apply advanced optical techniques to probe the phases of complex quantum materials. The main optical techniques are time-domain THz spectroscopy, transient grating spectroscopy, time-resolved magneto-optic Kerr effect, and second-harmonic generation. Examples of current projects are: ferromagnetic resonance in strontium ruthenate, spin propagation in metals and semiconductors, and quasiparticle recombination and diffusion in superconductors.