Vibrations Make Electrons Team Up
Electrons are typically considered solitary travelers, since their negative charges make them strongly repel one another. But two decades ago, scientists predicted that atomic vibrations inside a material could encourage electrons to move instead in coordinated groups [1]. Now Freek Massee at Paris-Saclay University and his colleagues have achieved the first direct observation of this effect at the atomic scale [2]. The findings could help scientists build on-demand sources of electron bunches, which are needed for electron-based quantum optics and many other emerging quantum technologies.
The idea behind the bunching effect is that when one electron tunnels through a nanoscale structure, it induces tiny vibrational excitations known as vibrons in the surrounding atoms. These vibrons briefly persist after that electron has passed, temporarily modifying the local electronic environment. This change makes it easier than it otherwise would be for further electrons to tunnel soon after the first one, inducing electron bunching. Direct atomic-scale visualization of this phenomenon has been lacking because conventional microscopes do not have the required temporal resolution.
To meet this demand, Massee and his colleagues developed a specialized low-temperature scanning tunneling microscope that can resolve small fluctuations in the tunneling current. Those fluctuations reveal whether the electrons are moving independently or in correlated groups. The researchers demonstrated their method using electrons tunneling through an iron impurity embedded in the semiconducting material bismuth selenide, and they consistently detected electron bunching. They suggest that the next step is to apply their method to molecular systems, which may exhibit stronger or more complex bunching.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- J. Koch and F. von Oppen, “Franck-Condon blockade and giant Fano factors in transport through single molecules,” Phys. Rev. Lett. 94, 206804 (2005).
- A. Maiti et al., “Evidence for atomic-scale vibron-mediated electron bunching,” Phys. Rev. Lett. 136, 236501 (2026).