Crossover from trion-hole complex to exciton-polaron in n-doped two-dimensional semiconductor quantum wells
Crossover from trion-hole complex to exciton-polaron in n-doped two-dimensional semiconductor quantum wells
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DOI：
10.1103/physrevb.98.235203
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发表时间：
2018-12-14
影响因子：
3.7
通讯作者：
Combescot, Monique
中科院分区：
文献类型：
--
作者：
Chang, Yia-Chung;Shiau, Shiue-Yuan;Combescot, Monique
我们对n掺杂二维（2D）和准2D半导体中的光吸收进行了理论研究，该研究考虑了光生激子与费米海（FS）电子通过（i）泡利阻挡、（ii）库仑屏蔽和（iii）的相互作用。FS电子-空穴对的激发-我们在这里仅限于一个。因此，我们处理的系统是由一个激子加上零或一个FS电子空穴对。在低掺杂时，系统基态主要由“trion-hole”-trion（两个相反自旋的电子加上一个价空穴）与FS空穴弱结合-具有小的激子分量组成。由于trion与光子耦合不良，最低吸收峰的强度较弱;由于两粒子和四粒子状态之间的耦合较大，由于激子分量的增长，最低吸收峰的强度随着掺杂而增加。随着掺杂浓度的进一步增加，由于FS电子的Pauli阻挡作用，三电子-空穴复合物的束缚减少，能量增加。较低的峰然后变得主要是由于由FS电子-空穴对修饰的激子，即激子-极化子。结果表明，n掺杂半导体量子阱威尔斯的吸收光谱呈现两个显著的吸收峰，最低峰的性质由三空穴转变为激子极化子。我们的工作也钉在后面的物理机制的增加与掺杂的三重空穴峰和激子-极化子峰之间的能量分离，甚至在反交叉，如实验观察到的。
We present a theoretical study of photoabsorption in n-doped two-dimensional (2D) and quasi-2D semiconductors that takes into account the interaction of the photocreated exciton with Fermi-sea (FS) electrons through (i) Pauli blocking, (ii) Coulomb screening, and (iii) excitation of FS electron-hole pairs-that we here restrict to one. The system we tackle is thus made of one exciton plus zero or one FS electron-hole pair. At low doping, the system ground state is predominantly made of a "trion-hole"-a trion (two opposite-spin electrons plus a valence hole) weakly bound to a FS hole-with a small exciton component. As the trion is poorly coupled to photon, the intensity of the lowest absorption peak is weak; it increases with doping, thanks to the growing exciton component, due to a larger coupling between two-particle and four-particle states. Under a further doping increase, the trion-hole complex is less bound because of Pauli blocking by FS electrons, and its energy increases. The lower peak then becomes predominantly due to an exciton dressed by FS electron-hole pairs, that is, an exciton-polaron. As a result, the absorption spectra of n-doped semiconductor quantum wells show two prominent peaks, the nature of the lowest peak turning from trion-hole to exciton-polaron under a doping increase. Our work also nails down the physical mechanism behind the increase with doping of the energy separation between the trion-hole peak and the exciton-polaron peak, even before the anticrossing, as experimentally observed.