Recording the synchronised dance of electrons in super-small particles
New research supported in part by the EU-funded SoftMeter and TOMATTO(opens in new window) projects shows how electrons excited by ultra-fast light pulses dance in unison around a particle less than a nanometre in diameter. The research team succeeded in measuring this dance of electrons with remarkable precision, making it the first time a measurement of this kind has been achieved on such a small scale. These results offer new insight into the nature of synchronised electron motion in subnanometre-sized systems and pave the way for new advances in nanoplasmonic applications. The synchronised motion of electrons – plasmonic resonance – is capable of trapping light for short periods of time. This ability has found application in areas ranging from the conversion of light into chemical energy to improvements in light-sensitive gadgets. However, up to now, measurements of plasmonic resonance in real time had only been possible in systems 10 nanometres wide or larger because of the ultra-fast timescale in which resonance occurs. Thanks to advances in laser technology, this is no longer the case. As the researchers describe in their paper(opens in new window) published in ‘Science Advances’, they were able to record the behaviour of electrons with precision in subnanometre football ball-shaped carbon molecules called buckminsterfullerenes, or buckyballs for short. The team used attosecond pulses – extremely short bursts of light pulses lasting for a billionth of a billionth of a second – to trigger and measure the movement of electrons in these 0.7-nanometres-in-diameter molecules. They precisely timed the process from the moment the light pulses excited the electrons to the instant the electrons were emitted, releasing excess energy from the buckyballs.
Dancing in unison
Each cycle was found to last between 50 and 300 attoseconds, and the measurements showed that the electrons were behaving with strong coherence, oscillating in unison. “These findings demonstrate, for the first time, that attosecond measurements can provide valuable insights into plasmonic resonances at scales smaller than a nanometer,” remarks Shubhadeep Biswas, the study’s lead author and a researcher at Max Planck Institute of Quantum Optics (Germany) and at the SLAC National Accelerator Laboratory (United States), in a SLAC news item(opens in new window). This research breakthrough enables scientists to measure an entire new range of ultra-small particles. “With this measurement, we are unlocking new insights into the interplay between electron coherence and light confinement at sub-nanometer scales,” states co-senior author Matthias Kling, a professor at the Max Planck Institute of Quantum Optics and a director at SLAC’s Linac Coherent Light Source(opens in new window). “This work demonstrates the power of attosecond techniques and opens the door to novel approaches in manipulating electrons in future ultrafast electronics, that could be operating at up to a million times higher frequencies than current technology.” Co-senior author Francesca Calegari, lead scientist at SoftMeter project coordinator Deutsches Elektronen-Synchrotron DESY, observes: “This cutting-edge research is opening new avenues for the development of ultra-compact, high-performance platforms, where light-matter interactions can be controlled by taking advantage of quantum effects emerging at the nanoscale.” The TOMATTO (The ultimate Time scale in Organic Molecular opto-electronics, the ATTOsecond) project ends in 2027. SoftMeter (Multi-messenger soft-field spectroscopy of molecular electronics at interfaces) ends in 2028. For more information, please see: SoftMeter project TOMATTO project website(opens in new window)
