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Session L21: Spins in 2D Materials

11:15 AM–2:15 PM, Wednesday, March 7, 2018
LACC Room: 309

Sponsoring Units: GMAG DMP FIAP DCOMP
Chair: Paul Crowell, Univ of Minn - Minneapolis

Abstract: L21.00006 : Spin and Valley Polarization Dynamics Probed by Time-Resolved Kerr Rotation in WSe₂

12:15 PM–12:27 PM

    Abstract  

Presenter:

Spencer Batalden
(Univ of Michigan - Ann Arbor)

Authors:

Spencer Batalden
(Univ of Michigan - Ann Arbor)

Xinlin Song
(Univ of Michigan - Ann Arbor)

Saien Xie
(Cornell University)

Kibum Kang
(Cornell University)

Jiwoong Park
(Cornell University)

Vanessa Sih
(Univ of Michigan - Ann Arbor)

Using time-resolved Kerr rotation measurements, we observe long-lived spin signals up to ~80 ns in the MOCVD-grown monolayer transition metal dichalcogenide (TMD) WSe₂ [1]. This signal is robust to transverse magnetic fields, providing evidence that the spin signals arise from the resident hole population. A recent study by Dey et al. has shown this robustness occurs solely in the p-type regime, due to spin-valley locking in the valence band [2]. Photoluminescence measurements also show a transition from free exciton to localized exciton emission as the temperature decreases. Wavelength-dependent Kerr rotation measurements then reveal that this polarization is only generated by excitation near the free exciton energy. Unlike a recent study on exfoliated MoSe₂ which shows long spin lifetimes at room temperature, our polarization decays quickly as the temperature is increased [3]. Combined, these measurements support the future use of TMDs for creating spintronic and valleytronic devices.
[1] X. Song et al., Nano Lett. 16, 5010 (2016)
[2] P. Dey et al., Phys. Rev. Lett. 199, 7401 (2017)
[3] M. Ersfeld, et al., arXiv:1708.00228v1