日期和时间Date & Time：20-April-2023（Thursday）3:30PM (Beijing time)

Zoom Meeting：ID：662 921 9901

报告人Speaker：Likun Wang, ICFO-The Institute of Photonic Sciences, Spain

主持人Host：Kai Chang，BAQIS

题目Title：Single Molecule Coherence with Femtosecond THz-STM

摘要Abstract 

A scanning tunneling microscope (STM) combined with femtosecond terahertz (THz) laser pulses can enable coherence measurements of single molecules. We report THz pump-probe measurements that demonstrate quantum sensing based on a hydrogen (H2) molecule in the junction created with an STM tip near a surface. Atomic-scale spatial and femtosecond temporal resolutions were obtained from this quantum coherence. The H2 acts as a two-level system (TLS) in a double-well potential, with its coherent oscillatory superposition exhibiting extreme sensitivity to the applied electric field and the underlying atomic composition and electrostatics of the copper nitride (Cu2N) monolayer islands grown on a Cu(100) surface. We acquired a series of time-lapsed images of THz induced rectification current of H2 over Cu2N islands for variable pump-probe delay times to visualize the heterogeneity of the chemical environment at sub-angstrom scale.

报告人简介About the speaker

Likun Wang, a postdoctoral fellow at ICFO Spain, graduated from the Department of Physics at the University of California, Irvine in 2022. His main research direction is to combine low-temperature scanning tunneling microscopy (STM) with femtosecond pulsed laser (near-infrared/terahertz) to detect and regulate the quantum coherence of surface-adsorbed single molecules and single atoms.