Electrical control of inter-dot electron tunneling in a quantum dot molecule

TL;DR

This study uses ultrafast spectroscopy to observe and control electron tunneling between quantum dots, revealing rapid, broadband tunneling mediated by phonon interactions, advancing quantum dot device understanding.

Contribution

It demonstrates direct measurement and control of inter-dot electron tunneling times and mechanisms using ultrafast spectroscopy, highlighting elastic and inelastic processes.

Findings

Ultrafast (<5 ps) tunneling occurs over ~8 meV bandwidth.

Resonant tunneling is mediated by elastic and inelastic processes.

Electron and hole tunneling times are separately measured.

Abstract

We employ ultrafast pump-probe spectroscopy to directly monitor electron tunneling between discrete orbital states in a pair of spatially separated quantum dots. Immediately after excitation, several peaks are observed in the pump-probe spectrum due to Coulomb interactions between the photo-generated charge carriers. By tuning the relative energy of the orbital states in the two dots and monitoring the temporal evolution of the pump-probe spectra the electron and hole tunneling times are separately measured and resonant tunneling between the two dots is shown to be mediated both by elastic and inelastic processes. Ultrafast (< 5 ps) inter-dot tunneling is shown to occur over a surprisingly wide bandwidth, up to ~8 meV, reflecting the spectrum of exciton-acoustic phonon coupling in the system.