Characterizing the rate and coherence of single-electron tunneling between two dangling bonds on the surface of silicon

TL;DR

This paper proposes a novel method to measure the coherence and tunneling rate of a single electron between two silicon dangling bonds using an atomic-force-microscope tip and midinfrared laser, revealing quantum dynamics through charge distribution symmetry.

Contribution

It introduces a new experimental scheme combining electrostatic bias and laser resonance to characterize coherent single-electron tunneling and decoherence in silicon surface dangling bonds.

Findings

Resonant laser induces symmetric charge distribution, indicating tunneling resonance.

The method can determine tunneling rates from charge distribution symmetry.

The approach reveals decoherence effects in single-electron tunneling.

Abstract

We devise a scheme to characterize tunneling of an excess electron shared by a pair of tunnel-coupled dangling bonds on a silicon surface -- effectively a two-level system. Theoretical estimates show that the tunneling should be highly coherent but too fast to be measured by any conventional techniques. Our approach is instead to measure the time-averaged charge distribution of our dangling-bond pair by a capacitively coupled atomic-force-microscope tip in the presence of both a surface-parallel electrostatic potential bias between the two dangling bonds and a tunable midinfrared laser capable of inducing Rabi oscillations in the system. With a nonresonant laser, the time-averaged charge distribution in the dangling-bond pair is asymmetric as imposed by the bias. However, as the laser becomes resonant with the coherent electron tunneling in the biased pair the theory predicts that the time-averaged charge distribution becomes symmetric. This resonant symmetry effect should not only reveal the tunneling rate, but also the nature and rate of decoherence of single-electron dynamics in our system.