[18p-D61-1~21] 10.4 Spintronics in semiconductor, topological material, superconductor, and multiferroics

5:30 PM - 5:45 PM JST(8:30 AM - 8:45 AM UTC)Presentation by Applicant for JSAP Young Scientists Presentation AwardEnglish Presentation

[18p-D61-17] Long-lived valley-polarization in suspended WSe2 monolayers strained by electrostatic pressure

〇Giacomo Mariani¹, Yoji Kunihashi¹, Louis Smet¹, Taro Wakamura¹, Satoshi Sasaki¹, Jun Ishihara², Makoto Kohda², Junsaku Nitta^1,2, Haruki Sanada¹ (1.NTT-BRL, 2.Tohoku Univ.)

Keywords:

monolayer,transition-metal dichalcogenides,kerr rotation

Transition-metal dichalcogenides (TMDs) monolayers have been emerging as a platform for hybridizing spintronics, valleytronics, and optoelectronics because of their direct bandgap and spin-valley-dependent optical transitions. However, the properties of TMD monolayers are sensitive to the interfacial inhomogeneities with their supporting substrate. Impurities and strain puddles create potential traps for charges which can affect the valley polarization. Previous studies evidenced that suspended monolayers have improved carrier mobility and are less sensitive to the dielectric screening of the substrate. However, the dynamics of the valley polarization of suspended monolayers have been mainly studied by photoluminescence (PL) spectroscopy, which limits the analysis to short-lived bright excitons and radiatively recombined carriers. We report the long lifetime of the valley polarization in a suspended WSe2 monolayer by a pump-probe Kerr rotation (KR) spectroscopy, measured at a temperature of 7 K. Compared to PL analysis, the KR signal is sensitive to both the radiative and non-radiative recombinations and thus can measure the valley polarization of long-lived complexes such as trions or resident carriers.