标题： 单层WSe$_2$导带电子的谷寿命 显示英文标题

标题： Valley lifetimes of conduction band electrons in monolayer WSe$_2$

摘要： 二维过渡金属二硫属化合物研究中的主要任务之一是确定谷寿命。 在本工作中，我们将时间分辨克尔旋转与电输运测量相结合，以探索单层WSe$_2$自由导带电子的栅极依赖谷寿命。 当将费米能级调至导带时，我们观察到相应的谷寿命显著减少，这与自旋-轨道和电子-声子散射一致。 我们通过光学激发的谷极化明亮三重态通过谷间散射散射到暗态来解释谷极化的形成。 此外，我们表明传统的时间分辨克尔旋转测量方案必须进行修改，以考虑光致栅极屏蔽效应。 忽视这种调整可能导致从栅极依赖光学测量中得出错误结论，并可能完全掩盖真正的栅极依赖谷动力学。 显示英文摘要

摘要： One of the main tasks in the investigation of 2-dimensional transition metal dichalcogenides is the determination of valley lifetimes. In this work, we combine time-resolved Kerr rotation with electrical transport measurements to explore the gate-dependent valley lifetimes of free conduction band electrons of monolayer WSe$_2$. When tuning the Fermi energy into the conduction band we observe a strong decrease of the respective valley lifetimes which is consistent with both spin-orbit and electron-phonon scattering. We explain the formation of a valley polarization by the scattering of optically excited valley polarized bright trions into dark states by intervalley scattering. Furthermore, we show that the conventional time-resolved Kerr rotation measurement scheme has to be modified to account for photo-induced gate screening effects. Disregarding this adaptation can lead to erroneous conclusions drawn from gate-dependent optical measurements and can completely mask the true gate-dependent valley dynamics.