Department of Physics, Boston University, 590 Commonwealth Ave, Boston, Massachusetts, 02215, USA.
Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road F165, Evanston, IL, 60208, USA.
Sci Rep. 2017 Oct 25;7(1):14062. doi: 10.1038/s41598-017-14378-w.
Monolayer molybdenum disulfide (MoS) has emerged as a model system for studying many-body physics because the low dimensionality reduces screening leading to tightly bound states stable at room temperature. Further, the many-body states possess a pseudo-spin degree of freedom that corresponds with the two direct-gap valleys of the band structure, which can be optically manipulated. Here we focus on one bound state, the negatively charged trion. Unlike excitons, trions can radiatively decay with non-zero momentum by kicking out an electron, resulting in an asymmetric trion photoluminescence (PL) peak with a long low-energy tail and peak position that differs from the zero momentum trion energy. The asymmetry of the trion PL peak and resulting peak red-shift depends both on the trion size and a temperature-dependent contribution. Ignoring the trion asymmetry will result in over estimating the trion binding energy by nearly 20 meV at room temperature. We analyze the temperature-dependent PL to reveal the effective trion size, consistent with the literature, and the temperature dependence of the band gap and spin-orbit splitting of the valence band. This is the first time the temperature-dependence of the trion PL has been analyzed with such detail in any system.
单层二硫化钼 (MoS) 已成为研究多体物理的模型体系，因为低维性降低了屏蔽作用，从而导致在室温下稳定的强束缚态。此外，多体态具有与能带结构的两个直接带隙谷对应的赝自旋自由度，可通过光学手段进行操纵。在这里，我们关注一种束缚态，即带负电荷的三重子。与激子不同，三重子可以通过踢出一个电子而以非零动量发生辐射衰变，从而导致不对称的三重子光致发光 (PL) 峰，其具有长的低能尾巴和不同于零动量三重子能量的峰位置。三重子 PL 峰的不对称性以及由此产生的峰红移既取决于三重子的大小，也取决于依赖于温度的贡献。忽略三重子的不对称性会导致在室温下高估三重子结合能近 20 meV。我们分析了温度相关的 PL，以揭示有效三重子大小，这与文献一致，以及价带的带隙和自旋轨道分裂的温度依赖性。这是首次在任何体系中如此详细地分析三重子 PL 的温度依赖性。
