Bipolaronic blockade effect in quantum dots with negative charging energy

TL;DR

This paper explores how negative charging energy in quantum dots leads to a bipolaronic blockade effect, significantly altering electron transport behavior compared to traditional Coulomb blockade, with observable experimental implications.

Contribution

It introduces the bipolaronic blockade effect in quantum dots with negative charging energy and analyzes its impact on conductance under various conditions.

Findings

Bipolaronic blockade suppresses low-bias conductance.

Conductance resonances are enhanced at large biases.

Magnetic field and coupling asymmetry tune conductance features.

Abstract

We investigate single-electron transport through quantum dots with negative charging energy induced by a polaronic energy shift. For weak dot-lead tunnel couplings, we demonstrate a bipolaronic blockade effect at low biases which suppresses the oscillating linear conductance, while the conductance resonances under large biases are enhanced. Novel conductance plateau develops when the coupling asymmetry is introduced, with its height and width tuned by the coupling strength and external magnetic field. It is further shown that the amplitude ratio of magnetic-split conductance peaks changes from 3 to 1for increasing coupling asymmetry. Though we demonstrate all these transport phenomena in the low-order single-electron tunneling regime, they are already strikingly different from the usual Coulomb blockade physics and are easy to observe experimentally.