二维材料中trions的变分优化轨道方法
Variationally optimized orbital approach to trions in two-dimensional materials
摘要：
本文用变分法研究了二维空间中的三重子，试波函数由二维slater型轨道的线性组合构成。用这种方法可以有效地计算出三电子的能级和波函数，并具有较好的精度。我们首先应用这种方法研究了二维类氢系统中的三电子能级，并在较宽的质量比和屏蔽长度范围内进行了计算。我们发现，基态trion是绑定的整个参数范围内，和一个激发态trion与反对称置换的电子与有限的角动量是绑定大的电子空穴质量比或长屏蔽长度。用本方法计算的基态三电子的结合能与用更复杂但计算量大的方法计算的结合能吻合得很好。然后，我们计算了各种单层过渡金属二硫属化物（TMDC）中的三价态，使用这种方法包括电子空穴交换（EHX）的相互作用。对于TMDC，我们发现EHX的影响可以在确定三离子结合能和稳定的激发态三离子的可能存在显着。
英文摘要：
In this work, trions in two-dimensional (2D) space are studied by variational method with trial wavefunctions being constructed by linear combinations of 2D slater-type orbitals (STOs). Via this method, trion energy levels and wavefunctions can be calculated efficiently with fairly good accuracy. We first apply this method to study trion energy levels in a 2D hydrogen-like system with respect to a wide range of mass ratios and screening lengths. We find that the ground-state trion is bound for the whole parameter range, and an excited-state trion with antisymmetric permutation of electrons with finite angular momentum is bound for large electron-hole mass ratios or long screening lengths. The binding energies of ground-state trions calculated by the present method agree well with those calculated by more sophisticated but computationally-demanding methods. We then calculate trion states in various monolayer transition metal dichalcogenides (TMDCs) by using this method with the inclusion of electron-hole exchange (EHX) interaction. For TMDCs, we found that the effect of EHX can be significant in determining the trion binding energy and the possible existence of stable excited-state trions.
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