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Strained bilayerWSe2with reduced exciton-phonon coupling
Physical Review B ( IF 3.7 ) Pub Date : 2020-03-23 , DOI: 10.1103/physrevb.101.115305
Ozgur Burak Aslan , Minda Deng , Mark L. Brongersma , Tony F. Heinz

We investigate excitonic absorption and emission in bilayer WSe2 under tensile strain. We observe a redshift of 110 meV in the energy of the A exciton absorption peak (at the direct gap at the K point in the Brillouin zone) under 2.1% uniaxial tensile strain. In addition, under the same strain, the spectral linewidth of the A exciton at room temperature decreases by a factor of 2, from 70 to 36 meV. We show that this decrease is a result of suppression of phonon-mediated exciton scattering channels. This suppression is associated with the relative upshift under strain of the Q valley in the conduction band (involved in the indirect exciton emission), which is nearly degenerate with the K valley (involved in the A exciton). We analyze the strain-dependent absorption and photoluminescence spectra to determine the relative positions of these valleys and to infer intervalley scattering rates. Our model describes well the decrease and the distinct trends in the A exciton linewidth of monolayer and bilayer WSe2 under strain. The results show that strain can be used to tune, as well as to probe, the relative energies of band extrema and exciton scattering channels in two-dimensional semiconductors.

中文翻译:

减少了激子-声子耦合的应变双层WSE2

我们研究双层中的激子吸收和发射 硒化钨2在拉伸应变下。我们观察到能量的110meV的红移一种 激子吸收峰(在 ķ点在布里渊区)在2.1%的单轴拉伸应变下。此外,在相同的应变下,一种室温下的激子降低了2倍,从70到36 meV。我们表明,这种减少是抑制声子介导的激子散射通道的结果。这种抑制作用与在压力下的相对升档有关。 导带中的波谷(涉及间接激子发射),随着 ķ 山谷(涉及 一种激子)。我们分析了应变依赖的吸收和光致发光光谱,以确定这些谷的相对位置,并推断intervalley散射率。我们的模型很好地描述了下降趋势和趋势一种 单层和双层的激子线宽 硒化钨2承受压力。结果表明,应变可用于调谐和探测二维半导体中带极值和激子散射通道的相对能量。
更新日期:2020-03-24
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