Theory of strong inelastic co-tunneling

TL;DR

This paper develops a theoretical framework for understanding conductance behavior in quantum dots with quantum point contacts, revealing how Coulomb blockade oscillations and conductance peaks evolve with temperature and contact symmetry.

Contribution

It introduces a comprehensive theory describing inelastic co-tunneling and conductance oscillations in quantum dots, extending previous models to include strong inelastic effects and asymmetry.

Findings

Conductance oscillations grow as temperature decreases.

Peak conductance approaches $e^2/ ext{h}$ for symmetric barriers at zero temperature.

Asymmetric barriers lead to conductance vanishing linearly with temperature.

Abstract

We develop a theory of the conductance of a quantum dot connected to two leads by single-mode quantum point contacts. If the contacts are in the regime of perfect transmission, the conductance shows no Coulomb blockade oscillations as a function of the gate voltage. In the presence of small reflection in both contacts, the conductance develops small Coulomb blockade oscillations. As the temperature of the system is lowered, the amplitude of the oscillations grows, and eventually sharp periodic peaks in conductance are formed. Away from the centers of the peaks the conductance vanishes at low temperatures as $T^2$, in agreement with the theory of inelastic co-tunneling developed for the weak-tunneling case. Conductance near the center of a peak can be studied using an analogy with the multichannel Kondo problem. In the case of symmetric barriers, the peak conductance at $T\to 0$ is of the order of $e^2/\hbar$. In the asymmetric case, the peak conductance vanishes linearly in temperature.