Speaker: Dr. Scott Crooker
Description: In semiconductor physics, many fundamental material properties relevant for optoelectronics (electron masses, dielectric parameters, etc) can be experimentally revealed via optical spectroscopy in sufficiently large magnetic fields. For the new family of monolayer transition-metal dichalcogenide (TMD) semiconductors such as MoS2 and WSe2, this magnetic field scale is substantial -- of order 100 tesla! - due to heavy carrier masses and huge exciton binding energies. Fortunately, modern pulsed magnets can achieve this scale. Using exfoliated monolayers affixed to single-mode optical fibers, we performed low-temperature magneto-absorption spectroscopy up to ~90T of all members of the monolayer TMD family. By following the diamagnetic shifts and valley Zeeman splittings of the exciton's 1s ground state and its excited 2s, 3s, ... ns Rydberg states, we determined exciton masses, radii, binding energies, dielectric properties, and free-particle bandgaps. These data provide essential ingredients for the rational design of optoelectronic van der Waals structures.
Presentation Slides: Revealing Fundamental Parameters of 2D Semiconductors via Optical Sectroscopy in (really) High Magnetic Fields (PDF)