磷烯中激子的各向异性Stark位移、场诱导解离和电吸收
Anisotropic Stark shift, field-induced dissociation, and electroabsorption of excitons in phosphorene
摘要：
我们计算结合能，斯塔克位移，电场诱导的解离速率，和Franz-Keldysh效应的激子在磷烯在各种介电环境。所有这三种效应都显示出对面内电场方向的显著依赖性，特别是在将电场从扶手椅旋转到Z字形轴时，解离速率降低了几个数量级。为了更好地理解数值离解率，我们推导出一个解析近似的各向异性率诱导的弱电场，从而推广了以前得到的结果为各向同性的二维半导体。这种近似是有效的，在弱场限制，通过比较它的准确率。各向异性也是明显的扶手椅和锯齿形组件的激子极化率张量，我们计算的五个最低的躺状态之间的巨大差异。正如预期的那样，我们还发现了更明显的斯塔克位移，无论是在扶手椅或锯齿形方向，这取决于所讨论的状态的对称性。最后，各向同性的相互作用势被证明是一个很好的近似更准确的各向异性的相互作用来自泊松方程，确认磷烯的各向异性在很大程度上是由于有效质量的方向依赖性。
英文摘要：
We compute binding energies, Stark shifts, electric-field-induced dissociation rates, and the Franz-Keldysh effect for excitons in phosphorene in various dielectric surroundings. All three effects show a pronounced dependence on the direction of the in-plane electric field, with the dissociation rates in particular decreasing by several orders of magnitude upon rotating the electric field from the armchair to the zigzag axis. To better understand the numerical dissociation rates, we derive an analytical approximation to the anisotropic rates induced by weak electric fields, thereby generalizing the previously obtained result for isotropic two-dimensional semiconductors. This approximation is shown to be valid in the weak-field limit by comparing it to the exact rates. The anisotropy is also apparent in the large difference between armchair and zigzag components of the exciton polarizability tensor, which we compute for the five lowest lying states. As expected, we also find much more pronounced Stark shifts in either the armchair or zigzag direction, depending on the symmetry of the state in question. Finally, an isotropic interaction potential is shown to be an excellent approximation to a more accurate anisotropic interaction derived from the Poisson equation, confirming that the anisotropy of phosphorene is largely due to the direction dependence of the effective masses.
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