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arXiv · 2008.03624

Large photoluminescence enhancement by an out-of-plane magnetic field in exfoliated WS$_2$ flakes

Sibai Sun·Jianchen Dang·Xin Xie·Yang Yu·Longlong Yang·Shan Xiao·Shiyao Wu·Kai Peng·Feilong Song·Yunuan Wang·Jingnan Yang·Chenjiang Qian·Zhanchun Zuo·Xiulai Xu
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Abstract

We report an out-of-plane magnetic field induced large photoluminescence enhancement in WS${}_2$ flakes at $4$ K, in contrast to the photoluminescence enhancement provided by in-plane field in general. Two mechanisms for the enhancement are proposed. One is a larger overlap of electron and hole caused by the magnetic field induced confinement. The other is that the energy difference between $\Lambda$ and K valleys is reduced by magnetic field, and thus enhancing the corresponding indirect-transition trions. Meanwhile, the Land\'e g factor of the trion is measured as $-0.8$, whose absolute value is much smaller than normal exciton, which is around $|-4|$. A model for the trion g factor is presented, confirming that the smaller absolute value of Land\'e g factor is a behavior of this $\Lambda$-K trion. By extending the valley space, we believe this work provides a further understanding of the valleytronics in monolayer transition metal dichalcogenides.

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Sibai Sun, Jianchen Dang, Xin Xie, Yang Yu, Longlong Yang, Shan Xiao, Shiyao Wu, Kai Peng, Feilong Song, Yunuan Wang, Jingnan Yang, Chenjiang Qian, Zhanchun Zuo, Xiulai Xu. 2020-08-09. Large photoluminescence enhancement by an out-of-plane magnetic field in exfoliated WS$_2$ flakes. https://doi.org/10.1088/0256-307x%2F37%2F8%2F087801

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