"Proximity Effects in Magnetic/TMD Heterostructures " with Professor Hao Zeng
From Lori D'Nicuola
Proximity Effects in Magnetic/TMD Heterostructures
Professor Hao Zeng
Professor of Physics, University at Buffalo, the State University of New York
The broken inversion symmetry together with strong spin orbit coupling leads to two degenerate yet inequivalent valleys (local extrema in electronic band structure) in monolayer transition metal dichalcogenides (TMDs), with opposite spin characters. The spin-locked valley states have been proposed for information applications, an area known as “valleytronics”. To manipulate the valley degree of freedom, the valley degeneracy can be lifted by external magnetic fields. However, the splitting value of ~0.2 meV/T is small, making valley control difficult. 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 field “amplifier”, we have achieved up to two orders of magnitude enhanced valley splitting in TMD/EuS heterostructures. More interestingly, the valley splitting of the two materials have opposite signs, suggesting the complex exchange interactions between the TMD and magnetic substrates. Towards the end, I will discuss a theoretical proposal to realize a “valley dark exciton transistor” and its implication for coherent control of valley states for quantum information.
NPJ Comp. Mater. 6, 90 (2020); Nature Comm. 10, 4163 (2019); Nature Nano. 12, 757, 2017.
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, UB Exceptional Scholar-Yong Investigator Award and Lixun Young Scientist Award from Chinese Academy of sciences. He is an editor of the Journal of Magnetism and Magnetic materials and an editorial board member of Chinese Physics B. He has published 120 papers in Journals including Nature, Nature Nano., PRL, Nano Letters, JACS, Adv. Mater. and Nano Energy. These papers have been cited for 17000 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.