论文标题
黑暗状态对WS2单层的激子重组的影响，如多个时间尺度的泵和探针光谱揭示
Dark-state impact on the exciton recombination of WS2 monolayers as revealed by multi-time-scale pump-and-probe spectroscopy
论文作者
论文摘要
过渡金属二进制二色剂单层的发光产量经常遭受长寿命的黑暗状态的形成，其中包括带有Intervalley辐射载体的激子，自旋 - 孔孔的过渡以及位于散布关系光锥外的大型质量动量。从明亮的激子状态到黑暗状态的有效放松抑制了光子发射的量子产率。此外，激发子的辐射重组受螺旋型激子 - 外激体散射的很大影响，该散射在室温下产生了另一个非辐射弛豫通道。在这里，我们表明，螺旋式型散射不仅在（明亮）激子之间促进，而且在激子和长寿的黑暗状态之间也促进了螺旋式散射。我们使用精心设计的泵和探针技术研究了与六角形BN的单层WS2的发光动力学。我们观察到，与螺旋型散射相关的发光猝灭发生在1-100微秒的时间尺度上，因此对应于相关的暗状态的寿命。测得的寿命的广泛分布意味着各种各样的长寿命状态对激子歼灭过程的影响。
The luminescence yield of transition metal dichalcogenide monolayers frequently suffers from the formation of long-lived dark states, which include excitons with intervalley charge carriers, spin-forbidden transitions, and a large center-of-mass momentum located outside the light cone of dispersion relations. Efficient relaxation from bright exciton states to dark states suppresses the quantum yield of photon emission. In addition, the radiative recombination of excitons is heavily influenced by Auger-type exciton-exciton scattering, which yields another nonradiative relaxation channel at room temperature. Here, we show that Auger-type scattering is promoted not only between (bright) excitons but also between excitons and long-lived dark states. We studied the luminescence dynamics of monolayer WS2 capped with hexagonal BN over broad time ranges of picoseconds to milliseconds using carefully designed pump-and-probe techniques. We observed that luminescence quenching associated with Auger-type scattering occurs on 1-100 microsecond time scales, which thus correspond to the lifetimes of the relevant dark states. The broad distribution of the measured lifetimes implies the impact of various types of long-lived states on the exciton annihilation process.
