Prof. Riccardo Comin

Professor Comin’s research explores the novel phases of matter that can be found in electronic solids with strong interactions, also known as quantum materials. In these systems, the interplay between different degrees of freedom – charge, spin, orbital, and lattice – leads to new flavors of emergent orders via the mechanism of electronic symmetry breaking. These phenomena include, among others: superconductivity, (anti)ferromagnetism, spin-density-waves, charge order, ferroelectricity, orbital order, and any combination thereof.

The group uses a combination of synthesis, scattering, and spectroscopy in order to obtain a comprehensive picture of these intriguing phenomena.

Photon scattering techniques represent one of the most effective toolsets to study and characterize symmetry breaking phenomena in solids. Among these, resonant X-ray scattering has the ability to reveal the spatial ordering of the spin/charge/orbital degrees of freedom, which is of primary relevance for the study of broken symmetries in quantum materials. We complement the X-ray work with table-top optical probes (Raman scattering and Kerr/Faraday effect) to study these phenomena and their spectroscopic signatures in the extended phase diagram — as a function of temperature, pressure, strain, and magnetic fields.

We additionally use angle-resolved photoemission spectroscopy (ARPES) to measure the energy-momentum spectrum of single-particle excitations in strongly-correlated electron systems and topological electronic materials. In the latter, our ARPES studies are focused on elucidating the source of Berry curvature in the electronic band structure of topological metals and semimetals realized from novel lattice geometries (collaboration with Joe Checkelsky).

On the synthesis front, we focus on the growth of van der Waals materials characterized by moderate to strong electronic correlations leading to broken symmetry phases including charge-density-waves and various forms of magnetic order. We seek to elucidate how these emergent collective orders evolve from the 3D (bulk) to the 2D (monolayer) limit, and as a function of carrier doping, in these exfoliable crystals.

The quantum materials we like to explore include transition metal oxides (high-temperature superconductivity, spin-orbit entanglement, multiferroicity, etc.), rare earth compounds, and topological insulators. We study single-crystalline materials, as well as thin films and heterointerfaces.