Effect of phonons on valley depolarization in monolayer WSe2

Vijila Chellappan; Ai Lin Christina Pang; Soumya Sarkar; Zi En Ooi; Kuan Eng Johnson Goh

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자료유형: 학술저널

저자정보: Vijila Chellappan (Institute of Materials Research and Engineering (IMRE)) Ai Lin Christina Pang (Institute of Materials Research and Engineering (IMRE)) Soumya Sarkar (NUS Nanoscience and Nanotechnology Initiative (NUSNNI)) Zi En Ooi (Institute of Materials Research and Engineering (IMRE)) Kuan Eng Johnson Goh (Institute of Materials Research and Engineering (IMRE))

저널정보: 대한금속·재료학회 Electronic Materials Letters Electronic Materials Letters Vol.14 No.6

발행연도: 2018.1

수록면: 766 - 773 (8page)

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In this paper, temperature dependence of the excitonic bands in a mechanically exfoliated tungsten diselenide (WSe 2 ) monolayeris studied using photoluminescence and circular dichroic photoluminescence (PL) in the temperature range between8 and 300 K. The peak energies associated with the neutral exciton (A), charged exciton (trion) and localized excitons areextracted from the PL spectra revealing a trion binding energy of around 30 meV. The circular dichroic PL measured at 8 Kshows about 45% valley polarisation that sharply reduces with increasing temperature to 5% at 300 K with photoexcitationenergy of 1.96 eV. A detailed analysis of the emission line-width suggests that the rapid decrease of valley polarisation withthe increase of temperature is caused by the strong exciton–phonon interactions which effi ciently scatter the excitons intodiff erent excitonic states that are easily accessible due to the supply of excess photoexcitation energy. The emission linewidthbroadening with the increase of temperature indicate residual exciton dephasing lifetime < 100 fs, that correlates withthe observed rapid valley depolarisation.

참고문헌 (15)

참고문헌 신청

Weijie Zhao / 2012 / Evolution of Electronic Structure in Atomically Thin Sheets of WS 2 and WSe 2 / ACS Nano 7(1):791~797

J. M. Riley / 2014 / Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor / Nature Physics 10(11):835~839

Sanfeng Wu / 2013 / Electrical tuning of valley magnetic moment through symmetry control in bilayer MoS2 / Nature Physics 9(3):149~153

Edbert J. Sie / 2015 / Valley-selective optical Stark effect in monolayer WS2 / Nature Materials 14(3):290~294

Hualing Zeng / 2012 / Valley polarization in MoS2 monolayers by optical pumping / Nature Nanotechnology 7(8):490~493

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