Kaplan Group — Condensed Matter Theory
We are a condensed matter theory group in the Department of Physics at the University of Central Florida. We study how electrons organize themselves in solids, and how that organization can be engineered, driven, and detected.
Our work focuses on the most fundamental questions governing strong interactions and the tunability of material properties with light. In equilibrium, we focus on the structure of the Bloch wavefunction, and its geometry. We study how it manifests itself in non-linear response, in light-matter interaction, and in exotic states of matter, such as exciton insulators and topological superconductors.
We use large-scale first-principles calculation (density functional theory, Wannier downfolding, constrained RPA) to get real material properties, diagrammatic and many-body techniques to handle interactions between electrons and with light, and symmetry analysis — magnetic space groups, crystal fields, atomic orbitals — to know in advance which effects are allowed and which are forbidden. Increasingly we also use machine learning, with a strong preference for models we can interpret rather than models that merely score well.
What we work on
Four threads, described in detail on the research page:
- Quantum geometry and nonlinear response — Berry curvature, the quantum metric, and their consequences for nonlinear optics and transport
- Topology and exotic phenomena — unconventional superconductivity, topological crystalline phases, excitons in topological matter
- Out-of-equilibrium order — light-driven phases, spatiotemporal order, ultrafast dynamics
- AI-inspired materials science — interpretable machine learning for the prediction of new materials
Selected results
We predicted superconductivity in twisted transition-metal dichalcogenides, driven by repulsive interactions rather than phonons. We identified a new anomalous nonlinear Hall effect in a topological antiferromagnet. We showed that optical pulses can induce Faraday-wave-like spatiotemporal order in quantum solids that outlives the pump by orders of magnitude, and that light-driven phases can remain stable against thermal disordering. Most recently we have used interpretable machine learning to propose de novo superconductors — compounds with no close analogue in the training set.
This work has appeared in Nature, Nature Nanotechnology, Nature Physics, ACS Nano, Nature Communications, Physical Review Letters, and PNAS, among others. A full list is on Google Scholar and arXiv.
Working with experiment
We collaborate closely and continuously with experimental groups. Long-running collaborations include the groups of W. Gao (Nanyang Technological University), W. Wu (Rutgers), A. Pasupathy (Columbia), A. Kogar (UCLA), S.-W. Cheong (Rutgers), and C.Z. Chang — spanning ARPES, scanning tunneling microscopy, ultrafast electron diffraction, nonlinear optics, and transport.
UCF is a one of the best places in the worls for this. The Department of Physics has a strong experimental condensed matter presence in quantum materials and ARPES, and CREOL, the College of Optics and Photonics, puts world-class ultrafast and nonlinear optics on the same campus — a natural pairing with our light-matter work.
Join us
We are recruiting. Two postdoctoral positions and one graduate student position are open — details on the open positions page.