Abstract: 2D semiconductors, such as the transition metal dichalcogenides, support highly controllable bright optically excited states. These states are interesting both for the insight that they provide into the properties of 2D materials and because of their very high controllability and potential for advancing applications, including those in quantum information science. One of the key features of the optical response of 2D semiconductors is the dominant role of excitonic interactions. The strong influence of these many-body effects reflects the reduced dimensionality combined with the reduced dielectric screening of atomically thin crystals. In our talk, we will review progress in understanding the nature of optically excited states in 2D monolayers and heterostructures. We will describe how excitonic states can be tuned and probed be altering the Coulomb interaction within the layer by various approaches, including through changes in the external dielectric environment and localized strain fields. The latter provides a route to site-controlled quantum emitters. We will also describe recent advances in applying time-resolved ARPES (angularly resolved photoemission spectroscopy) to examine the momentum-space character and dynamics of excitons in transition metal dichalcogenide semiconductors and the role of moiré effects in stacks of twisted layers.
Biography for Tony Heinz
Tony Heinz received a BS degree in Physics from Stanford University and a PhD degree, also in Physics, from UC Berkeley. He then joined the IBM Research Division in Yorktown Heights, NY as a research staff member. In 1995, he became a professor of Physics and Electrical Engineering at Columbia University. He joined Stanford University as a Professor of Applied Physics, with a concurrent appointment at SLAC National Accelerator Laboratory as a Professor of Photon Science in 2015. Heinz’s research on surfaces, interfaces, and 2D materials has applied laser spectroscopic techniques to elucidate the fascinating properties of the world of reduced-dimensional systems. His research has been recognized by the Isakson and Schawlow Prizes of the APS, among other distinctions.
JQI Seminars are held on Mondays during Fall and Spring semesters at 11:00 a.m. Eastern Time in Room 2400 of the Atlantic Building. University of Maryland affiliates may participate using Zoom. The seminars are also livestreamed on the JQI YouTube channel (https://www.youtube.com/user/JQInews), which supports audience participation in the chat interface.
You will need to bring your cell phone, so you can sign in. For Zoom, please submit a chat saying hello, so you can receive lunch. Lunch will be served after the seminar only to the individuals that have attended.