Show simple item record

dc.contributor.advisorXu, Xiaodong
dc.contributor.authorZhong, Ding
dc.date.accessioned2019-08-14T22:38:09Z
dc.date.submitted2019
dc.identifier.otherZhong_washington_0250E_20408.pdf
dc.identifier.urihttp://hdl.handle.net/1773/44425
dc.descriptionThesis (Ph.D.)--University of Washington, 2019
dc.description.abstractElectrons in layered van der Waals materials with a honeycomb lattice structure possess a valley degree of freedom in addition to charge and spin, which make van der Waals materials a tantalizing platform for valleytronics research. Among many candidates, transitional metal dichalcogenides (TMDs) have one of the most highly addressable valleys. For example, they possess valley optical selection rule which allows for interplay between light helicity and valley indexes; they also possess valley contrasting Berry curvature which allows for spatial separation of valley current without external field. In this thesis, we interface a van der Waals magnet—CrI3 with a representative TMDs—WSe2 to achieve unprecedented valley control in WSe2. Topics on optical studies on plain CrI3 is also covered. First, we demonstrate that strong exchange field and spin-selective charge hopping occurs at the interface between WSe2 and CrI3. The former leads to enhanced control of valley splitting, such as large valley splitting equivalent to Zeeman effect with 13T magnetic field, and rapid valley splitting switch nearly three orders of magnitude faster than can be achieved by the Zeeman effect in bare WSe2; the later leads to remarkable population control of WSe2. We then introduce layer-resolved proximity effects in WSe2/bilayer and trilayer CrI3 heterostructure and use this knowledge for revealing domain structure in CrI3 that has never been observed. Next, we unravel the excitation power dependent metamagnetic transition in CrI3, which is can be utilized for achieving continuous and reversible tuning of the valley splitting and valley polarization in WSe2. For the second part, which is the optical studies on plain CrI3, this thesis includes: Using magneto-optic Kerr effect to demonstrate that CrI3 is the world’s first discovered 2d magnet; its bilayer and trilayer have antiferromagnetically coupled ferromagnetic monolayer as their ground state; PL study on CrI3 reveals photoluminescence at ~1.1eV originated from Frenkel Exciton, with its helicity connected to the magnetic order of itself.
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.rightsnone
dc.subject2d Magnets
dc.subject2d material
dc.subjectHeterostructure
dc.subjectPhotoluminescence
dc.subjectTMDs
dc.subjectValleytronics
dc.subjectPhysics
dc.subjectCondensed matter physics
dc.subject.otherPhysics
dc.titleOptical Study of 2D Magnets and Their Heterostructures for Valleytronics
dc.typeThesis
dc.embargo.termsDelay release for 1 year -- then make Open Access
dc.embargo.lift2020-08-13T22:38:09Z


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record