Du Shaoqing, Hashikawa Yoshifumi, Ito Haruka, Hashimoto Katsushi, Murata Yasujiro, Hirayama Yoshiro, Hirakawa Kazuhiko
Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Nano Lett. 2021 Dec 22;21(24):10346-10353. doi: 10.1021/acs.nanolett.1c03604. Epub 2021 Dec 2.
Light molecules such as HO are the systems in which we can have access to quantum mechanical information on their constituent atoms. Here, we have investigated electron transport through HO@C single molecule transistors (SMTs). The HO@C SMTs exhibit Coulomb stability diagrams that show multiple tunneling-induced excited states below 30 meV. Furthermore, we have performed terahertz (THz) photocurrent spectroscopy on HO@C SMTs and confirmed the same excitations. From comparison between experiment and theory, the excitations observed below 10 meV are identified to be the quantum rotational excitations of the water molecule. Surprisingly, the quantum rotational excitations of both para- and ortho-water molecule are observed simultaneously even for a single water molecule, indicating that the fluctuation between the ortho- and para-water states takes place in a time scale shorter than our measurement time (∼1 min), probably by the interaction between the encapsulated water molecule and conducting electrons.
诸如HO这样的轻分子体系，我们能够从中获取其组成原子的量子力学信息。在此，我们研究了电子通过HO@C单分子晶体管（SMT）的传输。HO@C单分子晶体管呈现出库仑稳定性图，该图显示在30毫电子伏特以下存在多个隧穿诱导的激发态。此外，我们对HO@C单分子晶体管进行了太赫兹（THz）光电流光谱研究，并证实了相同的激发态。通过实验与理论的比较，发现在10毫电子伏特以下观察到的激发态是水分子的量子旋转激发态。令人惊讶的是，即使对于单个水分子，同时观察到了仲水分子和正水分子的量子旋转激发态，这表明仲水态和正水态之间的波动发生在比我们的测量时间（约1分钟）更短的时间尺度上，这可能是由于被包裹的水分子与传导电子之间的相互作用所致。
