Direct Determination of Band-Gap Renormalization in the Photoexcited Monolayer MoS2
Direct Determination of Band-Gap Renormalization in the Photoexcited Monolayer MoS2
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DOI：
10.1103/physrevlett.122.246803
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发表时间：
2019-06-21
影响因子：
8.6
通讯作者：
Zhu, Xiaoyang
中科院分区：
文献类型：
--
作者：
Liu, Fang;Ziffer, Mark E.;Zhu, Xiaoyang
单层半导体的一个关键特征，如过渡金属二硫属化物，是屏蔽不良的库仑势，这导致大的激子结合能（E-b）和载流子对准粒子带隙（E-g）的强重整化。由于E-b和E-g的变化相互抵消，后者很难确定，导致在不同的载流子密度下光学跃迁能量变化很小。在这里，我们量化的宏观单晶二硫化钼单层SiO2上的带隙重整化，使用时间和角度分辨的光电子能谱。在Mott阈值以上的激发密度，E-g减少多达360 meV。我们比较了载流子密度依赖的E-g与以前的理论计算，并显示了在量化的带隙中知道掺杂和激发密度的必要性。
A key feature of monolayer semiconductors, such as transition-metal dichalcogenides, is the poorly screened Coulomb potential, which leads to a large exciton binding energy (E-b) and strong renormalization of the quasiparticle band gap (E-g) by carriers. The latter has been difficult to determine due to a cancellation in changes of E-b and E-g, resulting in little change in optical transition energy at different carrier densities. Here, we quantify band-gap renormalization in macroscopic single crystal MoS2 monolayers on SiO2 using time and angle-resolved photoemission spectroscopy. At an excitation density above the Mott threshold, E-g decreases by as much as 360 meV. We compare the carrier density-dependent E-g with previous theoretical calculations and show the necessity of knowing both doping and excitation densities in quantifying the band gap.