限域在氮化硼纳米管中的低聚噻吩分子的稳定性与光电性质：多体理论方法
Stability and optoelectronic properties of oligothiophene molecules confined in boron-nitride nanotubes : A many-body theoretical approach
AI总结：
本研究采用多体理论方法，探究限域在氮化硼纳米管中的低聚噻吩分子的结构与光电性质，揭示了其结合能、滑动特性、带隙调控及激子相互作用等规律，修正了BN管仅作保护环境的结论。
AI中文摘要：
我们采用密度泛函理论、多体GW近似及Bethe-Salpeter方程方法，研究封装在氮化硼（BN）纳米管中的低聚噻吩（nT）分子的结构与光电性质。结果显示，当纳米管直径约为10埃时，结合能达到最大值，直径增大时结合能逐渐降低。nT分子可沿纳米管滑动，其波纹势小于室温热能，这一特性促进了分子的头-尾聚集。在电子性质方面，我们发现纳米管电子态的杂化效应远小于屏蔽效应，屏蔽效应可使nT的光发射带隙缩小多达1电子伏特。针对BN纳米管极化的简单模型表明，这类极化效应会随nT分子长度及BN纳米管直径的增大而减弱。与气相光学性质相比，结构弛豫、杂化及屏蔽效应可使孤立嵌入nT的吸收边红移多达250毫电子伏特。此外，对头-尾连接的六聚噻吩二聚体的研究揭示了激子-激子相互作用，该作用将吸收边分裂为最低亮激子，与暗峰间隔约75毫电子伏特，这表明nT链在BN管内形成时可能存在集体效应。我们的结果验证并澄清了实验数据，修正了绝缘BN纳米管仅作为封装分子保护环境的结论。
英文摘要：
We investigate the structural and optoelectronic properties of oligothiophene (nT) molecules encapsulated in boron-nitride (BN) nanotubes using density functional theory, many-body GW and Bethe-Salpeter equation approaches. We show that the binding energy is maximized for tube diameters of approximately 10 Å, decreasing gradually for larger diameters. The nT molecules can slide along the tube with a corrugation potential smaller than room temperature thermal energy, promoting their head-to-tail aggregation. Regarding the electronic properties, we find that hybridization with the tube electronic states has a much smaller effect than that of screening, which can close the nT photoemission gap by as much as an eV. A simple model for the polarization of the BN tube demonstrates how these polarization effects decrease with increasing nT molecule length and BN tube diameter. Compared to the gas phase optical properties, structural relaxation, hybridization, and screening can redshift the absorption onset by up to 250 meV for isolated intercalated nTs. Additionally, the study of a head-to-tail sexithiophene dimer reveals an exciton-exciton interaction that splits the absorption onset into a lowest bright exciton, separated by approximately 75 meV from a dark peak. This suggests possible collective effects upon the formation of nT chains inside BN tubes. Our results confirm and clarify experimental data, mitigating the conclusion that insulating BN tubes just act as a protecting environment for encapsulated molecules.
