Researchers from MIPT and international partners have experimentally confirmed that electrons can tunnel through a single atomic defect in groups rather than individually. This phenomenon occurs due to strong interaction between electrons and crystal lattice vibrations, known as phonons.
The team utilized a scanning tunneling microscope equipped with megahertz-range cryogenic measurement circuits to analyze electron tunneling statistics. The study focused on iron atoms embedded in a bismuth selenide crystal, a material characterized by significant electron-phonon coupling.
Measurements of shot noise revealed a Fano factor reaching 1.16, indicating super-Poissonian statistics. This confirms that electrons pass through the impurity atom with positive correlations. In contrast, iron dimers showed noise suppression due to Coulomb blockade.
Control tests conducted in magnetic fields up to 5 T showed no impact of spin dynamics on the effect. The study, published in Physical Review Letters, was supported by a grant from the Russian Ministry of Science and Higher Education under agreement number 075-15-2025-010.
