Abstract

Coupling of electrons to matter lies at the heart of our understanding of material properties such as electrical conductivity. Electron–phonon coupling can lead to the formation of a Cooper pair out of two repelling electrons, which forms the basis for Bardeen–Cooper–Schrieffer superconductivity. Here, we present our investigations of a single electron embedded in a Bose–Einstein condensate. We show that the electron can excite phonons and eventually trigger a collective oscillation of the whole condensate. We find that the coupling is surprisingly strong compared to that of ionic impurities, owing to the more favorable mass ratio. The electron is held in place by a single charged ionic core, forming a Rydberg bound state. This Rydberg electron is described by a wavefunction extending to a size of up to eight micrometres, comparable to the dimensions of the condensate. The Rydberg electron is interacting with several tens of thousands of condensed atoms contained within its orbit. We discuss experiments on in-situ electron orbital imaging, the investigation of phonon- mediated coupling of single electrons, and applications in quantum optics.

© 2014 Optical Society of America