Our research broadly encompasses the field of `quantum materials’- materials that exhibit properties that are fundamentally quantum mechanical in nature. Some examples are high-temperature superconductors, quantum-critical metals, and topological (`Weyl’) semimetals. The experiments combine custom-built apparatus with state of the art data acquisition and analysis, with the broad goal of uncovering the fundamental ingredients that lead to new states of matter. We use extreme environments, including low temperatures and high magnetic fields, to manipulate quantum materials and uncover what fundamental ingredients are necessary for the emergent phenomena they exhibit.
For example, an important question in high-Tc research is whether broken symmetry, like charge density wave order or nematicity, drives superconducting pairing. Another question is what happens to electrons in metals when you subject them to extremely high magnetic fields. For two-dimensional systems like graphene or GaAs/AlGaAs heterostructures, the fractional quantum Hall effect emerges. In three dimensional systems, however, this question is unresolved. The possibilities are rich and numerous, including Wigner crystallization, charge/spin/valley density waves, and excitonic insulators. The recent discovery of three dimensional topological (Dirac and Weyl) semimetals, along with advances in pulsed magnetic fields, has made this a very exciting topic.
Our primary techniques include electrical transport, torque magnetometry, and symmetry-sensitive ultrasonic techniques (resonant ultrasound spectroscopy (RUS) and pulse-echo ultrasound). The work often makes use of high magnetic fields: high fields can be used to suppress superconductivity, to add a new energy scale into the system and induce phase transitions, or to directly measure the electronic structure of metals.