Center for Correlated Electron Systems


Electronic structures of atomically thin transition metal dichalcogenides

January 22, 2016l Hit 878
Date : January 26, 2016 16:00 ~ 17:00
Speaker : Dr. Sung-Kwan Mo (Advanced Light Source, Lawrence Berkeley National Lab)
Location : Bldg. 19, Rm. 210
Layered transition metal dichalcogenides (TMDs) has recently gained intense interest due to their versatility towards novel optoelectric, photovoltaic, spintronics, and valleytronics applications, as well as potential for serving as a building block for van der Waals heterostructures with designed properties.
In this talk, I will first summarize combined angle-resolved photoemission (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS) investigation on the electronic structures of atomically thin MoSe2 and WSe2 films on bilayer graphene. Using ARPES, we have made a direct observation of a distinct transition from indirect to direct band gap at a single layer limit as well as clear signatures of spin-splitting. STS measurements find gigantic exciton energy ~ 0.55eV for monolayer due to the reduced screening in two dimensions.
Then I will introduce more recent findings -- the existence of metallic one-dimensional chains at the mirror twin boundaries of MoSe2 and the competition of charge density wave and superconductivity in NbSe2 thin films.