Quantum Confined Stark Effect Of Excitonic Transitions For Essays

The quantum-confined Stark shift was calculated, using a numerical method, for eight differently shaped simple Al0.4Ga0.6As/AlxGa1-xAs quantum wells. The dependence of the electron and heavy-hole ground-state interband transition energy on external electric field, quantum well profile and its thickness was investigated. Calculations also include the excitation binding energy, the overlap of the electron and hole wavefunctions and their average spatial separation. A wider well has a larger Stark shift, independent of its shape. An extensive comparison was made of the field response to differently shaped wells having the same zero-field electron ground-state energy (78 meV). The thinnest was a 51 AA wide square well and the thickest a 261 AA asymmetric triangular well. The symmetric and asymmetric triangular wells were found to exhibit the largest Stark shifts but also had a larger reduction of the overlap and exciton binding energy. The square well, on the contrary, had the smallest Stark shift but also smaller variation of the overlap and exciton binding energy. Other wells exhibited characteristics between these two extreme cases.

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Title: Quantum confined Stark effect in a MoS$_2$ monolayer van der Waals heterostructure

Authors:Jonas G. Roch, Nadine Leisgang, Guillaume Froehlicher, Peter Makk, Kenji Watanabe, Takashi Taniguchi, Christian Schönenberger, Richard J. Warburton

(Submitted on 26 Oct 2017)

Abstract: The optics of dangling-bond-free van der Waals heterostructures containing transition metal dichalcogenides are dominated by excitons. A crucial property of a confined exciton is the quantum confined Stark effect (QCSE). Here, such a heterostructure is used to probe the QCSE by applying a uniform vertical electric field across a molybdenum disulfide (MoS$_2$) monolayer. The photoluminescence emission energies of the neutral and charged excitons shift quadratically with the applied electric field provided the electron density remains constant, demonstrating that the exciton can be polarized. Stark shifts corresponding to about half the homogeneous linewidth were achieved. Neutral and charged exciton polarizabilities of $(7.8~\pm~1.0)\times 10^{-10}~\tr{D~m~V}^{-1}$ and $(6.4~\pm~0.9)\times 10^{-10}~\tr{D~m~V}^{-1}$ at relatively low electron density ($8 \times 10^{11}~\tr{cm}^{-2}$) have been extracted, respectively. These values are one order of magnitude lower than the previously reported values, but in line with theoretical calculations. The methodology presented here is versatile and can be applied to other semiconducting layered materials as well.

Submission history

From: Guillaume Froehlicher [view email]
[v1] Thu, 26 Oct 2017 15:17:21 GMT (3012kb,D)

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