Orateur: Prof. Yousoo KIM  (Surface and Interface Science Lab., Riken, Japan and Center for Quantum Conversion Research, IBS Gwangju, Korea)

Résumé : Energy conversion at the molecular scale is governed by the interplay of electronic, vibrational, and optical degrees of freedom, often through processes that remain hidden in ensemble-averaged measurements. In this talk, I will discuss our efforts to visualize and understand such processes at the level of individual molecules by combining scanning probe microscopy with optical and ultrafast spectroscopy.

I will first introduce how atomic-scale junctions can be used not only to image molecules, but also to probe their excited states, charge-transfer processes, and energy-dissipation pathways with unprecedented spatial resolution. Particular emphasis will be placed on single-molecule exciton dynamics, photocurrent generation, and vibration–phonon coupling at surfaces. I will then discuss our recent development of ultrafast THz-driven scanning tunneling microscopy, which provides access to excited-state dynamics with simultaneous atomic-scale spatial and picosecond temporal resolution.

These studies illustrate how local probes can reveal the elementary pathways through which energy is absorbed, converted, transported, and dissipated in individual quantum systems, providing a microscopic basis for understanding and ultimately controlling molecular-scale energy conversion.