Control “Valley” Properties using a Magnet - Dr. Hao Zeng / Department of Physics, University at Buffalo, the State University of New York, USA

o Dr. Hao Zeng irá discutir, no Café com Ciência, a aplicação de nanomateriais 2D.

Control “Valley” Properties using a Magnet

Palestrante: Dr. Hao Zeng

Afiliação: Department of Physics, University at Buffalo, the State University of New York, USA

Data: 13/05/2019 (segunda-feira)

Horário: 12h45

Local: Anfiteatro I do IF/UFG

Abstract:

Exploiting the “valley” degree of freedom to store and manipulate information is an emerging direction of condensed matter physics, and provides a novel paradigm for future electronics. Transition metal dichalcogenides (TMDs), such as MoS2, WS2 and WSe2, are semiconductor analogy of graphite with atomic layers bonded together by Van der Waals interactions. A monolayer TMD with broken inversion symmetry possesses two degenerate valleys that can be selectively excited by circularly polarized light. Breaking the valley degeneracy allows convenient control of valley degree of freedom. This can be done by applying an external magnetic field to Zeeman split the band edge states. We demonstrate that the valley properties can be controlled by magnetism. We show that valley splitting can be enhanced by more than an order of magnitude, utilizing the interfacial exchange field from a ferromagnetic substrate. We further show that both the magnitude and sign of the valley spitting can be tuned by the exchange field, which is otherwise unattainable in an external field. This approach opens up a new avenue for valley control for “valleytronics” applications.