单层WSe2、MoSe2激子发光的压力诱导K-Λ交互转变

Pressure-induced K-Λ Crossover of Excitons Emissions in Monolayer WSe_2 and MoSe_2

采用机械剥离法在金刚石对顶砧中制备了单层WSe_2和MoSe_2样品,利用高压微区荧光光谱测量技术,在氩传压介质环境下对其激子发光行为进行了高压调控研究。其中单层WSe_2的中性和负电激子演化趋势在2. 43 GPa处出现拐点,单层MoSe_2中性激子发光在3. 7 GPa处发生了劈裂。结合第一性原理计算分析,确认该不连续现象的产生机制为压力诱导的导带底K-Λ交互转变。该结果可以扩大至整个二维层状材料体系,为发展激子器件垫定基础。

Monolayer MoSe2 and WSe2 samples were prepared by mechanical exfoliation in diamond anvil cell（DAC）. The high-pressure micro-area fluorescence spectroscopy technique was used to study excitons emission behavior under pressure in argon pressure-transmitting medium（PTM）. The neutral and negative exciton evolutionary trends of monolayer WSe2 showed an inflection point at 2.43 GPa, and the neutral exciton emission of monolayer MoSe2 appeared a new split peak at 3.7 GPa. Combined with the first-principles calculation and analysis, we confirmed that the mechanism of these discontinuities is the pressure-induced conduction band bottom K-Λ crossover. This result can be extended to the entire two-dimensional layered material family, and laying foundation for the development of exciton devices.