Name of the speaker: Dr. Yang Zhang
Position:Associate Professor                                   
Organization: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China
Nationality: China


The Title of Speech: Investigating coherent intermolecular dipole-dipole coupling
with STM induced luminescence technique

Biography of the Speaker:Dr. Yang Zhang received his B. Sc. and Ph. D. degrees in physics from University of Science and Technology of China in 2004 and 2010, respectively. From November 2010 to July 2013, he worked as a postdoctoral researcher in French National Centre for Scientific Research. Since August 2013, he is an associated professor in University of Science and Technology of China. His research interests lie in single-molecule optoelectronics and single-molecule plasmonics/nano-photonics.
Abstract of Speech:The tunneling electrons in a scanning tunneling microscope (STM) can not only be used to image and manipulate surface nanostructures with atomic resolution, but also excite light emission from STM junctions by inelastic tunneling electrons. STM induced luminescence (STML) technique, combining the STM with optical detection, can do nano-imaging beyond diffraction limit, which provide photon images with unmatchable spatial resolution down to sub-nanometer scale. Coherent intermolecular dipole-dipole coupling plays a key role in various resonant energy transfer and luminescence phenomena, from exciton dynamics in molecular aggregates and biological light-harvesting complexes to quantum state engineering in entangled molecular systems. Extensive efforts have been made to investigate the coherent behavior from the energy, and time domains. However, it is still unknown how such coherence and related exciton delocalization are manifested in real space, due to the diffraction limitation in conventional optics. Here, we demonstrate the real-space visualization of coherent intermolecular dipole-dipole coupling for constructed molecular structures. Through spatially and spectrally resolved fluorescence imaging of an entangled molecular dimer, the coupling strength of coherent dipole-dipole interactions for various coupling modes has been directly determined. Moreover, we have visualized in real space the orbital-bonding-like patterns of transition probability amplitude distributions for all these modes. With the knowledge thus gained, we also achieve electrically driven 'single-molecule' single-photon superradiance in an entangled system of well-defined molecular oligomers.