Energy Spectrum of Two-Dimensional Excitons in a Nonuniform Dielectric Medium
Energy Spectrum of Two-Dimensional Excitons in a Nonuniform Dielectric Medium
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DOI：
10.1103/physrevlett.123.136801
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发表时间：
2019-09-23
影响因子：
8.6
通讯作者：
Potemski, M.
中科院分区：
文献类型：
--
作者：
Molas, M. R.;Slobodeniuk, A. O.;Potemski, M.
我们证明，在半导体过渡金属二硫族化合物的单层（MLs）中，s型Rydberg系列激子态遵循一个简单的能量阶梯：epsilon(n) = -Ry*/(n + delta)(2), n = 1,2，…，其中Ry*非常接近由ML周围介质的介电常数和减少的有效电子空穴质量标度的Rydberg能量，而ML极化率仅由delta来解释。通过对六方氮化硼（hBN）封装的高质量WSe2 ML的磁光测量结果的激子共振实验数据的分析，证明了这一点，并且当以修正的克拉泽势的形式近似电子-洞势时，用解析可解的薛定谔方程很好地再现了这一点。将我们的惯例应用于其他封装在hBN中的MoSe2， WS2, MoS2 MLs，我们估计了每个研究结构的表观幅度。有趣的是，发现WSe2和MoS2单层的δ都接近于零，这意味着这些二维结构中激子态的能量阶梯类似于三维氢原子的里德堡态。
We demonstrate that, in monolayers (MLs) of semiconducting transition metal dichalcogenides, the s-type Rydberg series of excitonic states follows a simple energy ladder: epsilon(n) = -Ry*/(n + delta)(2), n = 1, 2,..., in which Ry* is very close to the Rydberg energy scaled by the dielectric constant of the medium surrounding the ML and by the reduced effective electron-hole mass, whereas the ML polarizability is accounted for only by delta. This is justified by the analysis of experimental data on excitonic resonances, as extracted from magneto-optical measurements of a high-quality WSe2 ML encapsulated in hexagonal boron nitride (hBN), and well reproduced with an analytically solvable Schrodinger equation when approximating the electron-hole potential in the form of a modified Kratzer potential. Applying our convention to other MoSe2, WS2, MoS2 MLs encapsulated in hBN, we estimate an apparent magnitude of delta for each of the studied structures. Intriguingly, delta is found to be close to zero for WSe2 as well as for MoS2 monolayers, what implies that the energy ladder of excitonic states in these two-dimensional structures resembles that of Rydberg states of a three-dimensional hydrogen atom.