Excitons, quasiparticles composed of an electron and a hole, play an important role in optical responses in low-dimensional nanostructures. In this work, we have investigated exciton diffusion in monolayer $\mathrm{Mo}{\mathrm{Se}}_2$ encapsulated between flakes of hexagonal boron nitride ($h\mathrm{BN}/\mathrm{MoS}{\mathrm{e}}_2/h\mathrm{BN}$). Through photoluminescence imaging and numerical solution of the two-dimensional diffusion equation, we revealed that temperature dependence of exciton mobility, ${\mu }_{\mathrm{ex}}$, in $h\mathrm{BN}/\mathrm{MoS}{\mathrm{e}}_2/h\mathrm{BN}$ shows a nonsaturating increase at low temperature, which is qualitatively different from those of quantum wells composed of compound semiconductors. The ultraflat structure of monolayer $\mathrm{Mo}{\mathrm{Se}}_2$ in $h\mathrm{BN}/\mathrm{MoS}{\mathrm{e}}_2/h\mathrm{BN}$ probably leads to the suppression of charged-impurity scattering and surface-roughness scattering.

中文翻译：

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激子扩散inhBN包裹的单层MoSe2

激子是由电子和空穴组成的准粒子，在低维纳米结构的光学响应中起着重要作用。在这项工作中，我们研究了激子在单层中的扩散$莫{硒}_2$ 封装在六方氮化硼薄片之间（$H\mathrm{国阵}/\mathrm{硫化钼}{\mathrm{Ë}}_2/H\mathrm{国阵}$）。通过光致发光成像和二维扩散方程的数值解，我们发现激子迁移率的温度依赖性，${\mu }_{前}$，在 $H\mathrm{国阵}/\mathrm{硫化钼}{\mathrm{Ë}}_2/H\mathrm{国阵}$图1显示了在低温下的非饱和增加，这在质量上与由化合物半导体组成的量子阱的增加不同。单层的超扁平结构$莫{硒}_2$ 在 $H\mathrm{国阵}/\mathrm{硫化钼}{\mathrm{Ë}}_2/H\mathrm{国阵}$ 可能导致带电杂质散射和表面粗糙度散射的抑制。