Effect of Phonons on Valley Depolarization in Monolayer WSe2

被引：13

作者：

Chellappan, Vijila ^{[1
]}

Pang, Ai Lin Christina ^{[1
]}

Sarkar, Soumya ^{[2
,3
]}

Ooi, Zi En ^{[1
]}

Goh, Kuan Eng Johnson ^{[1
,4
]}

机构：

[1] ASTAR, IMRE, 08-03,2 Fusionopolis Way, Singapore 138634, Singapore

[2] Natl Univ Singapore, NUS Nanosci & Nanotechnol Initiat NUSNNI, 11-T Lab,5A Engn Dr 1, Singapore 117411, Singapore

[3] NUS Grad Sch Integrat Sci & Engn NGS, 05-01,28 Med Dr, Singapore 117456, Singapore

[4] Natl Univ Singapore, Dept Phys, Singapore 117576, Singapore

来源：

ELECTRONIC MATERIALS LETTERS | 2018年 / 14卷 / 06期

关键词：

Transition metal dichalcogenides; Valley polarisation; Potoluminescence; Tungsten diselenide; MOS2; POLARIZATION; COHERENCE; GAP; WS2;

D O I：

10.1007/s13391-018-0086-2

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

In this paper, temperature dependence of the excitonic bands in a mechanically exfoliated tungsten diselenide (WSe2) monolayer is studied using photoluminescence and circular dichroic photoluminescence (PL) in the temperature range between 8 and 300K. The peak energies associated with the neutral exciton (A), charged exciton (trion) and localized excitons are extracted from the PL spectra revealing a trion binding energy of around 30meV. The circular dichroic PL measured at 8K shows about 45% valley polarisation that sharply reduces with increasing temperature to 5% at 300K with photoexcitation energy of 1.96eV. A detailed analysis of the emission line-width suggests that the rapid decrease of valley polarisation with the increase of temperature is caused by the strong exciton-phonon interactions which efficiently scatter the excitons into different excitonic states that are easily accessible due to the supply of excess photoexcitation energy. The emission line-width broadening with the increase of temperature indicate residual exciton dephasing lifetime <100fs, that correlates with the observed rapid valley depolarisation. [GRAPHICS] .

引用

页码：766 / 773

页数：8

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