My research explores the optical and electronic properties of novel nanoscale materials. My primary goal is to understand the fundamental physical properties of atomically thin two-dimensional materials like graphene and ultrathin transition metal dichalcogenide crystals. We utilize diverse optical spectroscopic techniques such as absorption, scattering, and photoluminescence spectroscopy to examine the electronic transitions in these materials, and terahertz, infrared and Raman spectroscopy to characterize the phonons — lattice vibrations. An important capability of our research is probing the dynamics of these materials by using femtosecond laser radiation coupled to emission spectroscopy techniques across the spectral range, extending from the terahertz to the ultraviolet.
My group identified the transition metal dichalcogenides (TMDCs), e.g., WSe2, and MoTe2, as materials that can be produced, studied, and manipulated in the form of atomically thin layers. We have shown that these materials are highly tunable through the application of electric/magnetic fields and, on the nanometer‐scale, through control of strain and the dielectric environment. We are examining excitonic states with the aim to create new classes of quantum materials such as excitonic insulators and excitonic condensates. Twisted-bilayer graphene has demonstrated the remarkable potential of engineered atomically thin materials to host unexpected quantum states. When two adjacent layers or graphene are twisted with respect to each other by exactly an angle of 1.1 degrees, a variety of emergent phenomena appear, including unconventional superconductivity. We are interested in extended such studies to other kinds of two-dimensional materials and examining twisted-layer TMDC structures to look for Mott-insulating and superconducting behaviors and other emergent phenomena.
Emergent Phenomena in Quantum Systems
Stanford University, Department of Applied Physics