Periodic Reporting for period 1 - STED (Real Space-Time imaging and control of Electron Dynamics)
Periodo di rendicontazione: 2023-08-01 al 2025-07-31
The interaction of light and matter plays a fundamental role in many natural processes, such as photosynthesis, vision, and bioluminescence, and has been pivotal in the development of photovoltaics, lasers, and optical communications. At the heart of chemical reactivity lies the ultrafast motion of electrons within molecules, which holds the promise for future technological advances. However, this electronic motion occurs on an extremely fast timescale, femtoseconds, and within spatial scales on the order of picometers.
To better understand electron dynamics inside molecules, there is a need for novel experimental tools that offer simultaneous femtosecond temporal and picometer spatial resolutions, enabling direct observation of light-matter interactions at their natural scales. Existing European facilities predominantly use ultrashort light sources that provide spatially averaged information, leaving a gap in local, real-time imaging capabilities.
The STED project addresses this gap by focusing on a complementary, so far barely explored approach: to image ultrafast electronic motion in individual molecules in real time but also in real space, with femtosecond and picometer resolutions, respectively, by combining ultrashort laser pulses with a scanning tunneling microscope (STM). The project addresses two key technological challenges: (1) the creation of hybrid light-matter quantum states in strongly coupled molecule-cavity systems, and (2) the detailed investigation of charge transfer processes between individual donor and acceptor molecules.
This research program positions the STED project to advance the frontiers of nanoscale quantum science and facilitate the development of transformative technologies in quantum information processing, ultrafast photonics, and energy-efficient nanoscale devices.
To better understand electron dynamics inside molecules, there is a need for novel experimental tools that offer simultaneous femtosecond temporal and picometer spatial resolutions, enabling direct observation of light-matter interactions at their natural scales. Existing European facilities predominantly use ultrashort light sources that provide spatially averaged information, leaving a gap in local, real-time imaging capabilities.
The STED project addresses this gap by focusing on a complementary, so far barely explored approach: to image ultrafast electronic motion in individual molecules in real time but also in real space, with femtosecond and picometer resolutions, respectively, by combining ultrashort laser pulses with a scanning tunneling microscope (STM). The project addresses two key technological challenges: (1) the creation of hybrid light-matter quantum states in strongly coupled molecule-cavity systems, and (2) the detailed investigation of charge transfer processes between individual donor and acceptor molecules.
This research program positions the STED project to advance the frontiers of nanoscale quantum science and facilitate the development of transformative technologies in quantum information processing, ultrafast photonics, and energy-efficient nanoscale devices.
The first scientific objective involved building a novel experimental setup, integrating a low temperature scanning tunneling microscope (STM) with both continuous-wave and pulsed laser sources. The developed technology enables local spectroscopic measurements of individual molecules and achieves a temporal resolution down to the picosecond scale.
The second objective aimed at providing fundamental insights into strong light-matter interactions in single molecules within a tunable pico-cavity. While strong coupling in molecular systems was not achieved, the project succeeded in creating and controlling hybrid light-matter quantum states (Floquet states) within field emission resonances of a metallic STM nanocavity under continuous‑wave laser excitation.
For the third objective, it was addressed the study of charge transfer between individual donor and acceptor molecules. A novel experimental methodology to measure absorption-like spectra on single molecules adsorbed on metallic surfaces was developed.
In addition to the core objectives of the proposal, three further research directions were pursued: (1) implementation of a Hanbury Brown-Twiss interferometer in the STM setup for photon correlation measurements, (2) measurement of ultrafast hot carrier dynamics in a well-defined picocavity and in a single graphene nanoribbon, (3) investigation of asymmetric scattering of electron standing waves at monoatomic height Bi(111) steps, revealing the influence of spin texture.
The second objective aimed at providing fundamental insights into strong light-matter interactions in single molecules within a tunable pico-cavity. While strong coupling in molecular systems was not achieved, the project succeeded in creating and controlling hybrid light-matter quantum states (Floquet states) within field emission resonances of a metallic STM nanocavity under continuous‑wave laser excitation.
For the third objective, it was addressed the study of charge transfer between individual donor and acceptor molecules. A novel experimental methodology to measure absorption-like spectra on single molecules adsorbed on metallic surfaces was developed.
In addition to the core objectives of the proposal, three further research directions were pursued: (1) implementation of a Hanbury Brown-Twiss interferometer in the STM setup for photon correlation measurements, (2) measurement of ultrafast hot carrier dynamics in a well-defined picocavity and in a single graphene nanoribbon, (3) investigation of asymmetric scattering of electron standing waves at monoatomic height Bi(111) steps, revealing the influence of spin texture.
The STED project has advanced the capabilities of scanning tunneling microscopy by incorporating both continuous-wave and pulsed laser sources, enabling local spectroscopic measurements of individual molecules with picometer spatial and picosecond temporal resolution.
Key findings of the project include the creation and manipulation of hybrid light-matter quantum states in metallic nanocavities, the development of a new methodology for retrieving absorption-like spectra at the single-molecule level, the investigation of ultrafast hot carrier dynamics in individual graphene nanoribbons, and the demonstration of spin-dependent electron scattering at atomic defects driven by spin-orbit coupling.
To maximize the impact of these advances, next steps include integrating a femtosecond laser source to push the temporal resolution towards the limits of electron dynamics and extending research to organic molecular systems. These further implementations are essential for deeper insights into the role of atomic defects in charge transfer efficiency and for unraveling the mechanisms that govern the formation of hybrid quantum states involving individual molecules.
Key findings of the project include the creation and manipulation of hybrid light-matter quantum states in metallic nanocavities, the development of a new methodology for retrieving absorption-like spectra at the single-molecule level, the investigation of ultrafast hot carrier dynamics in individual graphene nanoribbons, and the demonstration of spin-dependent electron scattering at atomic defects driven by spin-orbit coupling.
To maximize the impact of these advances, next steps include integrating a femtosecond laser source to push the temporal resolution towards the limits of electron dynamics and extending research to organic molecular systems. These further implementations are essential for deeper insights into the role of atomic defects in charge transfer efficiency and for unraveling the mechanisms that govern the formation of hybrid quantum states involving individual molecules.