Low-temperature annihilation rate for quasilocalized excitons in monolayer MoS2

The strong Coulomb forces in monolayer transition metal dichalcogenides ensure that optical excitation of band electrons gives rise to Wannier-Mott excitonic states, each of which can be conceptualized as a composite of a Gaussian wavepacket corresponding to center-of-mass motion and an orbital state corresponding to the motion of the electron and hole about the center-of-mass. Here, we show that at low temperature in monolayer MoS2, given quasi-localized excitons and consequently a significant inter-exciton spacing, the excitons undergo dipole-dipole interaction and annihilate one another in a manner analogous to Auger recombination. To construct our model, we assume that each exciton is localized in a region whose length is on the same scale as the excitonic diameter, thus causing the exciton to behave in a fermionic manner, while the distance between neighboring excitons is much larger than the exciton diameter. We construct the orbital ladder operators for each exciton and apply Fermi's Golden Rule to derive the overall recombination rate as a function of exciton density.

单层过渡金属二硫化物中强大的库仑力确保了能带电子的光激发会产生万尼尔 - 莫特激子态，其中每一个激子态都可被概念化为一个对应于质心运动的高斯波包和一个对应于电子和空穴围绕质心运动的轨道态的组合。在此，我们表明在单层二硫化钼低温条件下，鉴于准局域化激子以及由此产生的较大的激子间距，激子会发生偶极 - 偶极相互作用，并以类似于俄歇复合的方式相互湮灭。为构建我们的模型，我们假设每个激子局域在一个长度与激子直径处于同一量级的区域内，从而使激子表现出费米子的行为，而相邻激子之间的距离远大于激子直径。我们为每个激子构建轨道阶梯算符，并应用费米黄金定则推导出作为激子密度函数的总复合率。