Geometric blockade in a quantum dot coupled to two-dimensional and three dimensional electron gases

TL;DR

This paper investigates how the shape of electronic states in a quantum dot influences tunneling rates and current blockade phenomena when coupled to 2D and 3D electron gases, revealing a geometric current blockade effect.

Contribution

It introduces the concept of geometric blockade in quantum dots coupled to different dimensional electron gases and analyzes the eigenstate-dependent tunneling behavior.

Findings

Observation of bias-dependent geometric current blockade

Identification of metastable triplet states affecting transport

Asymmetric Coulomb diamond widening due to state shape

Abstract

We fabricated a quantum dot coupled laterally to a two-dimensional electron gas and vertically to a three-dimensional electron gas in order to investigate the eigenstate dependence of tunneling rate to these gases. We observed a bias-dependent ``geometric" current blockade. By tunneling via the asymmetric couplings, population inversion is induced and a dark metastable triplet state is revealed. The metastable state stops the current transport process, suppresses the current and asymmetrically widens the Coulomb diamond. By analyzing the current as a function of source-drain and gate voltage and the magnetic field, we concluded that this effect is due to the geometric shape of the electronic states in the dot and the current is limited by the tunneling rate due to the eigenstates, that is, artificial $\sigma$-coupling and $\pi$-coupling.