University of Waterloo
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
Phone: (519) 888-4567 ext 32215
Fax: (519) 746-8115
Fire restoration work is expected to continue into early November. The main stairwell and office wing on both second and third floors of the Physics building will be closed until necessary repairs to the main stairwell are completed.
Administrative offices have been relocated to PHY 345.
Please contact individual faculty members to request appointments, as many faculty have been relocated during this process.
Please do not cross any caution tapes whilst in the building.
Department of Physics
University of Toronto
Prof. Yang received her B.S. in physics and mathematics from Tsinghua University (2007) and her Ph.D. in physics from the University of California, Berkeley (2013). Then she worked as a Los Alamos Director’s Postdoctoral Fellow at the National High Magnetic Field Laboratory, Los Alamos. She joined the Department of Physics, University of Toronto as an assistant professor in September 2016. She was awarded the CIFAR Azrieli Global Scholar Fellowship in 2016 and Canada Research Chair in 2017.
Interest in atomically-thin transition metal dichalcogenide (TMD) semiconductors such as MoS2 and WSe2 has exploded in the last few years, driven by the new physics of coupled spin/valley degrees of freedom and their potential for new spintronic and ‘valleytronic’ devices. Although robust spin and valley degrees of freedom have been inferred from polarized photoluminescence (PL) studies of excitons, PL timescales are necessarily constrained by short-lived (1–30 ps) recombination timescales of excitons. Direct probes of spin and valley dynamics of the resident electrons and holes in n-type or p- type doped TMD monolayers, which may persist long after recombination ceases, are still at a relatively early stage.
In this work, we directly measure the coupled spin-valley dynamics of resident electrons and resident holes in n-type and p-type monolayer TMD semiconductors using time-resolved Kerr rotation. Very long relaxation timescales in the nanosecond to microsecond range are observed at low temperatures – orders of magnitude longer than typical exciton lifetimes. In contrast with III-V or II-VI semiconductors, electron spin relaxation in monolayer MoS2 is found to accelerate rapidly in small transverse magnetic fields (By). This indicates a novel mechanism of electron spin dephasing in monolayer TMDs that is driven by rapidly-fluctuating internal spin- orbit fields that, in turn, are due to fast electron scattering between the K and K’ conduction bands . More recent studies of gated TMD monolayers also allow observation of very long spin/valley relaxation of resident holes, a consequence of spin-valley locking . These studies provide direct insight into the physics underpinning the spin and valley dynamics of resident electrons and holes in 2D TMD semiconductors.
 L. Yang et al., Nature Physics 11, 830 (2015).  P. Dey et al., Phys. Rev. Lett. 119, 137401 (2017).