Laboratory for Semimetal Electronics

The future will be determined by the materials that we create.

Our materials are usually disordered at the atomic scale. There are rich and exotic quantum phenomena which we cannot see due to this disorder. In technology, we overly rely on a few key players, such as silicon, where we have invested decades in material optimization and device fabrication.

Molecular beam epitaxy, affectionately known as “spray painting with atoms”, is our most powerful technique for synthesizing crystalline materials with atomic precision. Gallium arsenide, synthesized by epitaxy, holds the record for the highest mobility material that humanity can create. Advanced epitaxial synthesis has the potential to create new materials with exceptional performance.

And yet, in many ways, we perform epitaxy in the dark, with limited information and control.

The dynamics of growth, the nature of disorder and the ultimate limitations on material quality are a mystery. Synthesis is highly sensitive to experimental details and difficult to master theoretically.

We aim to bring together new optical and electronic techniques to measure & control epitaxial films during growth, shining light on the magic of materials synthesis. By exploring photoluminescence, Raman scattering, second harmonic generation, ellipsometry, electron spectroscopy—in situ and in real time—we aim to create new high-mobility materials hosting new quantum states of matter. The additional in situ data will allow us to bring in machine learning to autonomously dial in growth conditions, reduce turnaround time and accelerate material development.

We also aim to structure materials using the physics of synthesis—reproducibly, scalably, avoiding lithography and resist, with critical interfaces and device structures formed and encapsulated under ultrahigh vacuum.

We are using these techniques to tackle some of the most important problems in science. Semiconductors tailored to photonics. Epitaxial superconductors to improve the coherence time of qubits. Topological superconductors and quantum Hall states hosting emergent anyons. Weyl semimetals for terahertz optoelectronics and photovoltaics. See below a snapshot of our current interests.

Image credits: Geometric linking number. Christina Pouss, Max-Planck-Institut für Chemische Physik fester Stoffe; Chromium dioxide angle-resolved photoemission spectrum. Belopolski et al. Unpublished; Colorful braids. E. Conover. Physicists have 'braided' strange quasiparticles called anyons. ScienceNews, 2020; DNA. H. Ledford. Nature 634, 1029 (2024).