Hao Zeng, Department of Physics, University at Buffalo, the State University of New York, USA
Abstract: The spin-locked valley states in monolayer transition metal dichalcogenides (TMDs) have been proposed for classical and quantum information applications. Valley polarization can be realized by applying a magnetic field to Zeeman split the band edge states. However, the small splitting value poses challenges for valley control. In this talk I will discuss an approach of using the proximity effect from a ferromagnetic substrate to enhance the valley splitting in monolayer TMDs. Using magnetic semiconductor EuS as a substrate in the WSe2/EuS heterostructure, we have achieved a valley splitting of 2.5 meV/T. In WS2/EuS, the splitting value is further increased to ~16 meV/T. These results suggest effective amplification of an external magnetic field by up to two orders of magnitude, and the mechanism of the exchange will be discussed. Towards the end of this talk, I will discuss our recent efforts to realize covalent 2D magnets and 2D magnet/TMD heterostructures using dative epitaxy, a newly discovered epitaxial growth mode.
Bio Hao Zeng received his B.S. degree from Nanjing University, China and Ph.D. from University of Nebraska-Lincoln, both in physics. He was a postdoc fellow at IBM Thomas J Watson Research Center between 2001 and 2004. He then joined the Physics Department at the University at Buffalo, the State University of New York as an Assistant Professor. In 2014 he was promoted to full Professor. He is the recipient of an IBM Research Division Award, NSF CAREER award, Lixun Young Scientist Award from Chinese Academy of sciences and UB Exceptional Scholar Awards. He is an editor of the Journal of Magnetism and Magnetic materials. He has published 150 papers with a total cited of 20,000 times. Hao Zeng’s research area is in condensed matter and materials physics. His present research interests focus on nanoscale magnetism and spintronics, unconventional chalcogenide semiconductors and bio-applications of magnetic nanoparticles.