Fractional plateaus in the Coulomb blockade of coupled quantum dots

TL;DR

This paper investigates the ground-state properties of coupled quantum dots in Coulomb blockade, revealing fractional charge steps and phase behavior influenced by tunneling and electrostatic coupling.

Contribution

It demonstrates fractional Coulomb staircase behavior and phase transitions in double-dot systems with varying tunneling strengths and electrostatic interactions.

Findings

Charge exhibits e/2 steps with halved capacitance peaks.

Fractional plateaus are significantly altered by tunneling strength.

An intermediate phase emerges with increasing slope of fractional plateaus.

Abstract

Ground-state properties of a double-large-dot sample connected to a reservoir via a single-mode point contact are investigated. When the interdot transmission is perfect and the dots controlled by the same dimensionless gate voltage, we find that for any finite backscattering from the barrier between the lead and the left dot, the average dot charge exhibits a Coulomb-staircase behavior with steps of size e/2 and the capacitance peak period is halved. The interdot electrostatic coupling here is weak. For strong tunneling between the left dot and the lead, we report a conspicuous intermediate phase in which the fractional plateaus get substantially altered by an increasing slope.