Wigner islands with electrons over helium

TL;DR

This paper reports the first experimental investigation of Wigner islands formed by electrons over helium, analyzing their addition spectrum and confirming electron ordering through comparison with simulations.

Contribution

It introduces the first experimental study of electron Wigner islands over helium and validates their ordered state via comparison with Monte Carlo simulations.

Findings

Experimental addition spectra measured for electrons over helium.

Confirmation of electron ordering in Wigner islands.

Agreement between experimental data and Monte Carlo simulations.

Abstract

We present here the first experimental study of Wigner islands formed by electrons floating over helium. Electrons are trapped electrostatically in a mesoscopic structure covered with a helium film, behaving as a quantum dot. By removing electrons one by one, we are able to find the addition spectrum, i.e. the energy required to add (or extract) one electron from the trap with occupation number $N$. Experimental addition spectra are compared with Monte Carlo simulations for the actual trap geometry, confirming the ordered state of electrons over helium in the island.