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arXiv 1609.06329cond-mat.mes-hall
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二维半导体中Trion吸收特性的多体理论

Many-Body Theory of Trion Absorption Features in Two-Dimensional Semiconductors

Dmitry K. Efimkin, Allan H. MacDonald

摘要:

最近的光学研究表明,单层过渡金属十硫属化物的激子吸收特性分裂成两个广泛分离的峰值在有限的载流子密度。额外的峰通常归因于三电子的存在,即两个电子和一个空穴或一个电子和两个空穴的束缚态。在这里,我们认为,在密度范围内的trion峰是很好地解决,它不能被解释为弱耦合三体系统,而适当的图片,而不是一个在其中的激子穿着与费米海的过剩载流子的相互作用。这种耦合将激子光谱分成较低能量的吸引激子-极化子分支(通常被识别为三子分支)和较高能量的排斥激子-极化子分支(通常被识别为激子分支)。我们计算了电导率的频率和掺杂依赖性,发现:(i)分裂随过量准粒子的费米能线性变化;(ii)在高载流子密度下,三电子峰占主导地位;(iii)三电子峰宽远小于激子峰宽。我们的结果与最近的实验结果吻合得很好。

英文摘要:

Recent optical studies of monolayer transition metal dechalcogenides have demonstrated that their excitonic absorption feature splits into two widely separated peaks at finite carrier densities. The additional peak is usually attributed to the presence of trions, bound states of two electrons and a hole or an electron and two holes. Here we argue that in the density range over which the trion peak is well resolved, it cannot be interpreted in terms of weakly coupled three-body systems, and that the appropriate picture is instead one in which excitons are dressed by interactions with a Fermi sea of excess carriers. This coupling splits the exciton spectrum into a lower energy attractive exciton-polaron branch, normally identified as a trion branch, and a higher energy repulsive exciton-polaron branch, normally identified as an exciton branch. We have calculated the frequency and doping dependence of the optical conductivity and found that: (i) the splitting varies linearly with the Fermi energy of the excess quasiparticles; (ii) the trion peak is dominant at high carrier densities; (iii) and the trion peak width is considerably smaller than that of the excitonic peak. Our results are in good agreement with recent experiments.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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