[8p-Z08-1~8] 10.4 Semiconductor spintronics, superconductor, multiferroics

[8p-Z08-2] Excitation energy dependence of valley polarization in monolayer WS₂ treated by organic acid

〇(M1)Takashi Kimura¹, Eito Asakura¹, Jack Alexander-Webber², Arelo O. A Tanoh³, Hope Bretscher³, Stephan Hofmann², Akshay Rao^3,4, Shutaro Karube^1,5, Junsaku Nitta^1,5,6, Makoto Kohda^1,5,6,7 (1.Tohoku Univ., 2.Dept. of Engineering, Univ. of Cambridge, 3.Cavendish Lab., 4.Dept. of Chemistry, Univ. of Cambridge, 5.CSRN, Tohoku Univ., 6.CSIS, Tohoku Univ., 7.FRiD, Tohoku Univ.)

Keywords:spintronics, valley, TMDC

Recently, the valley polarization of exciton and stabilization of trion emission in addition to the exciton has been observed in monolayer WS₂ treated by organic acid like oleic acid(OA). In this research, we investigated the excitation energy dependence of the valley polarization for trion in OA-treated monolayer WS₂ by the photoluminescence (PL) measurement. We observed two different peaks in the PL spectra which are originated from singlet and triplet trions. By increasing the excitation laser energy, singlet trion intensity is reduced around 2.17eV. On the other hand, the degree of valley polarization for singlet trion is slightly increased with the excitation energy. Moreover, triplet trion shows much higher valley polarization than that of singlet trion, which is promising for using triplet trion as highly efficient spin polarized emitter. Further analysis to clarify the origin of higher valley polarization n triplet trion will be discussed in the presentation.