论文标题
单层中的动量分辨激动量耦合和山谷两极分化动力学WS $ _2 $
Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS$_2$
论文作者
论文摘要
单层过渡金属二分法源中布里渊区的激子状态之间的耦合会导致超快谷去极化。使用时间和角度分辨光发射，我们提出单层WS $ _2 $中激子耦合的动量和能量分辨的测量。通过比较完整的4D（$ k_x，k_y，e，t $）数据集，在线性和循环极化激发之后，我们就可以删除Intertangle Intertalley和Interavalley Inveciton耦合动力学。以激子绑定能量基础而不是激发能量记录，我们观察到B $ _ {1S} $ ixciton和$ _ {n> 1} $状态之间的强烈混合。通过Intervalley耦合（例如K $^ - $ $ \ rightarrow $ k $^+$）观察到的激素能量和动量分布表明，优势谷去极化机制可以保留Ickiton的结合能量和中心中心动量，与InterveAlley Coulomb Exchange保持一致。在更长的时间尺度上，激子松弛伴随着动量空间分布的收缩。
Coupling between exciton states across the Brillouin zone in monolayer transition metal dichalcogenides can lead to ultrafast valley depolarization. Using time- and angle-resolved photoemission, we present momentum- and energy-resolved measurements of exciton coupling in monolayer WS$_2$. By comparing full 4D ($k_x, k_y, E, t$) data sets after both linearly and circularly polarized excitation, we are able to disentangle intervalley and intravalley exciton coupling dynamics. Recording in the exciton binding energy basis instead of excitation energy, we observe strong mixing between the B$_{1s}$ exciton and A$_{n>1}$ states. The photoelectron energy and momentum distributions observed from excitons populated via intervalley coupling (e.g. K$^-$ $\rightarrow$ K$^+$) indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and center-of-mass momentum, consistent with intervalley Coulomb exchange. On longer timescales, exciton relaxation is accompanied by contraction of the momentum space distribution.
