Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65 Tesla.
Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65 Tesla.
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DOI：
10.1038/ncomms10643
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发表时间：
2016-02-09
影响因子：
16.6
通讯作者：
Crooker SA
中科院分区：
文献类型：
--
作者：
Stier AV;McCreary KM;Jonker BT;Kono J;Crooker SA
在块体和量子限制半导体中，磁光研究历来在确定激子的基本参数（尺寸、结合能、自旋、维数等）方面发挥着重要作用。在这里，我们报告了原子薄WS2和MoS2在65 T高磁场中的低温偏振反射光谱。A和B激子都表现出类似的塞曼分裂，约为-230 μeV T−1（g因子≃−4），从而量化了单层过渡金属二硫化物中的谷塞曼效应。至关重要的是，这些大磁场还允许观察单层 WS2 中 A 和 B 激子的小二次抗磁位移，从中计算出~1.53 和~1.16 nm 的半径。此外，当在非局部介电屏蔽模型中进行分析时，这些抗磁位移还限制了 A 和 B 激子结合能的估计（分别为 410 和 470meV，使用自由电子质量 0.16 倍的减少的 A 激子质量）。这些结果凸显了高磁场在理解新型二维材料方面的实用性。 自旋自由度和谷自由度在二维过渡金属二硫属化物中耦合。在这里，作者使用高磁场光学测量二硫化钨和二硫化钼中的谷塞曼效应和反磁激子位移，并确定激子结合能。
In bulk and quantum-confined semiconductors, magneto-optical studies have historically played an essential role in determining the fundamental parameters of excitons (size, binding energy, spin, dimensionality and so on). Here we report low-temperature polarized reflection spectroscopy of atomically thin WS2 and MoS2 in high magnetic fields to 65 T. Both the A and B excitons exhibit similar Zeeman splittings of approximately −230 μeV T−1 (g-factor ≃−4), thereby quantifying the valley Zeeman effect in monolayer transition-metal disulphides. Crucially, these large fields also allow observation of the small quadratic diamagnetic shifts of both A and B excitons in monolayer WS2, from which radii of ∼1.53 and ∼1.16 nm are calculated. Further, when analysed within a model of non-local dielectric screening, these diamagnetic shifts also constrain estimates of the A and B exciton binding energies (410 and 470 meV, respectively, using a reduced A exciton mass of 0.16 times the free electron mass). These results highlight the utility of high magnetic fields for understanding new two-dimensional materials. The spin and valley degrees of freedom are coupled in two-dimensional transition-metal dichalcogenides. Here, the authors use high magnetic fields to optically measure the valley Zeeman effect and diamagnetic exciton shift in tungsten disulphide and molybdenum disulphide, and determine the exciton binding energies.