Imaging and manipulating electrons in a 1D quantum dot with Coulomb blockade microscopy

TL;DR

This paper explores how Coulomb blockade microscopy can differentiate electronic states in a 1D quantum dot, reveal electron interactions, and map potential landscapes by analyzing shifts in Coulomb blockade peaks with a movable tip.

Contribution

It demonstrates the use of Coulomb blockade microscopy to distinguish electronic states, observe electron transfer, and map potential landscapes in quantum dots with a movable tip.

Findings

Weak tip potential can differentiate high density and Wigner crystal states.

Strong negative tip potential can partition the quantum wire and move electrons.

Micrographs can estimate electron interaction strength and map impurity potentials.

Abstract

Motivated by the recent experiments by the Westervelt group using a mobile tip to probe the electronic state of quantum dots formed on a segmented nanowire, we study the shifts in Coulomb blockade peak positions as a function of the spatial variation of the tip potential, which can be termed "Coulomb blockade microscopy". We show that if the tip can be brought sufficiently close to the nanowire, one can distinguish a high density electronic liquid state from a Wigner crystal state by microscopy with a weak tip potential. In the opposite limit of a strongly negative tip potential, the potential depletes the electronic density under it and divides the quantum wire into two partitions. There the tip can push individual electrons from one partition to the other, and the Coulomb blockade micrograph can clearly track such transitions. We show that this phenomenon can be used to qualitatively estimate the relative importance of the electron interaction compared to one particle potential and kinetic energies. Finally, we propose that a weak tip Coulomb blockade micrograph focusing on the transition between electron number N=0 and N=1 states may be used to experimentally map the one-particle potential landscape produced by impurities and inhomogeneities.