title: Nuclear quantum effects of hydrogen bonds probed by tip-enhanced inelastic electron tunneling.
abstract: We report the quantitative assessment of nuclear quantum effects on the strength of a single hydrogen bond formed at a water-salt interface, using tip-enhanced inelastic electron tunneling spectroscopy based on a scanning tunneling microscope. The inelastic scattering cross section was resonantly enhanced by "gating" the frontier orbitals of water via a chlorine-terminated tip, so the hydrogen-bonding strength can be determined with high accuracy from the red shift in the oxygen-hydrogen stretching frequency of water. Isotopic substitution experiments combined with quantum simulations reveal that the anharmonic quantum fluctuations of hydrogen nuclei weaken the weak hydrogen bonds and strengthen the relatively strong ones. However, this trend can be completely reversed when a hydrogen bond is strongly coupled to the polar atomic sites of the surface.
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.affiliation: School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.
authors.forename: Jing-Tao
authors.initials: JT
authors.lastname: Lü
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China. School of Physics and Electronics, Hunan University, Changsha 410082, P. R. China.
authors.forename: Yexin
authors.initials: Y
authors.lastname: Feng
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
authors.forename: Ji
authors.initials: J
authors.lastname: Chen
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
authors.forename: Jinbo
authors.initials: J
authors.lastname: Peng
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
authors.forename: Zeren
authors.initials: Z
authors.lastname: Lin
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
authors.forename: Xiangzhi
authors.initials: X
authors.lastname: Meng
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China.
authors.forename: Zhichang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: School of Physics, Peking University, Beijing 100871, P. R. China. Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China. xzli@pku.edu.cn egwang@pku.edu.cn yjiang@pku.edu.cn.
authors.forename: Xin-Zheng
authors.initials: XZ
authors.lastname: Li
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China. Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China. xzli@pku.edu.cn egwang@pku.edu.cn yjiang@pku.edu.cn.
authors.forename: En-Ge
authors.initials: EG
authors.lastname: Wang
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China. Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China. xzli@pku.edu.cn egwang@pku.edu.cn yjiang@pku.edu.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Jiang