Sarah Grefe

Assistant Professor - Condensed Matter Experiment

Research Interests

  • Condensed matter theory
  • Computational physics
  • Quantum materials systems
  • Nonequilibrium phenomena

Quantum materials are those that form macroscopically measurable phases which emerge as the collective action of billions upon billions of quantum mechanical 'degrees of freedom,' such as particle spin, particle charge, orbital character, crystal lattice configuration, or nontrivial wavefunction topology. For instance, in a ferromagnet, the magnetic quantum spin moments of each iron atom collectively aligning produces the net magnetization field that allows it to stick to a steel refrigerator. In quantum materials, we aim to understand how remarkable phases like superconductivity can arise in seemingly unrelated compounds, and how making tiny changes to the same system might tune it like a radio from one quantum phase to another, and how to reliably design a material to produce a novel quantum phase or exotic quasiparticle. Such fundamental physics uncovers functionality that can be used for future sensing and computing device components.

I study quantum phases, quantum phase transitions, and nonequilibrium phenomena in quantum materials using theoretical and computational methods. I calculate new ways to measure signatures of topological metals in the strongly correlated regime – that is, where the interactions between the system’s many electrons is significant enough to alter its fundamental behavior. Since the energy scales involved with quantum materials is very small (typically all low temperature), it turns out that even small energy scale perturbations can produce extreme responses that render the system out-of-equilibrium or far-from-equilibrium. Though nonequilibrium phenomena pose some theoretical hurdles, nonequilibrium responses are filled with richly detailed information about the electrons in the system and thus opportunities to better characterize quantum materials.

See also:

Education

  • Ph.D. Rice University, 2020
  • M.S. CSU Long Beach, 2013
  • B.S. CSU Long Beach, 2011