Research

Solid. Liquid. Gas. These are the phases of matter we are used to in every day life. But within crystals, there are a plethora of electronic phases, many of them co-existing and/or competing with each other. External factors such as defects or strain can tip the system towards one phase over another. Here, our group intentionally decorates the surfaces of 2D materials with various atomic species to induce different macroscopic states, such as bond- or charge-density waves and topological phases.

"Quantum materials" is a term that often refers to materials that host a macroscopic, phase-coherent quantum state, such as superconductivity or charge density wave. Probes such as STM have been critical to understanding the static atomic-scale properties of these systems. But how do these states respond to electromagnetic fields that cause electrons to move and current to flow? Here, our group is performing experiments that image how collective equilibrium charge currents flow in these complex systems and react to atomic-scale disorder.

Physical properties ultimately derive from a material's crystal structure: having certain atomic species arranged in a specific geometric pattern. What happens, then, when a material is strained? How do changes in bond alignment and electron-lattice interactions affect a material's electronic properties? Our group is pursuing in situ STM/ARPES measurements as a function of strain in order to learn (i) how novel phases of matter respond to strain levels of variable strength and geometry, and (ii) how material failure (e.g. fracture) emerges at the atomic level.

Collecting STM/STS data can be time-consuming: Taking anywhere from minutes to several days. Quasi-particle interference (QPI) measurements, in particular, require careful thought into the scan parameters (length, pixel resolution) so that the relevant QPI image has the correct momentum-space extent and resolution. Here, we have developed PyAtoms, a GUI for real-time simulation of 2D materials and stacked heterostructures displaying moiré effects.

Photoluminescence (light in-light out) is a powerful tool for studying quantum materials, elucidating transitions between electronic energy levels. A distant cousin, STM-induced luminescence (STML), harnesses the STM tip as an atomic source of electroluminescence (charge in-light out). Here, we are developing STML capabilities to precisely tailor the light emission from the surface of 2D materials.