The crystal structure, stability, electronic, and optical properties of the Ta2NiSe5 monolayer have been investigated using first-principles calculations in combination with the Bethe–Salpeter equation. The results show that it is feasible to directly exfoliate a Ta2NiSe5 monolayer from the low-temperature monoclinic phase. The monolayer is stable and behaves as a normal narrow-gap semiconductor with neither spontaneous excitons nor non-trivial topology. Despite the quasi-particle and optical gaps of only 266 and 200 meV, respectively, its optically active exciton has a binding energy up to 66 meV and can exist at room temperature. This makes it valuable for applications in infrared photodetection, especially its inherent in-plane anisotropy adds to its value in polarization sensing. It is also found that the inclusion of spin–orbit coupling is theoretically necessary to properly elucidate the optical and excitonic properties of a monolayer.

中文翻译：

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Ta2NiSe5 单层的电子和光学特性：第一性原理研究


Ta2NiSe5 单层的晶体结构、稳定性、电子和光学性质已使用第一性原理计算结合 Bethe-Salpeter 方程进行了研究。结果表明，从低温单斜相中直接剥离 Ta2NiSe5 单分子层是可行的。单层是稳定的，表现为普通的窄间隙半导体，既没有自发激子，也没有非平凡的拓扑。尽管准粒子和光间隙分别只有 266 和 200 meV，但其光活性激子的结合能高达 66 meV，并且可以在室温下存在。这使得它在红外光探测中的应用很有价值，尤其是其固有的平面内各向异性增加了它在偏振传感中的价值。研究还发现，自旋-轨道耦合的加入在理论上对于正确阐明单层的光学和激子特性是必要的。