Two-channel Kondo physics in tunnel-coupled double quantum dots

TL;DR

This paper theoretically explores the conditions under which two-channel Kondo physics can be observed in tunnel-coupled double quantum dots, highlighting the challenges in experimental realization due to low temperature requirements.

Contribution

It provides a detailed theoretical analysis using the two-impurity Anderson model and numerical renormalization group, clarifying the feasibility of observing 2CK physics in quantum dot systems.

Findings

2CK physics is theoretically possible but requires temperatures lower than experimental capabilities.

Finite magnetic fields preserve the quantum phase transition related to 2CK, offering a tuning method.

Experimental observation of 2CK in this setup remains highly challenging due to temperature constraints.

Abstract

We investigate theoretically the possibility of observing two-channel Kondo (2CK) physics in tunnel-coupled double quantum dots (TCDQDs), at both zero and finite magnetic fields; taking the two-impurity Anderson model (2AIM) as the basic TCDQD model, together with effective low-energy models arising from it by Schrieffer-Wolff transformations to second and third order in the tunnel couplings. The models are studied primarily using Wilson's numerical renormalization group. At zero-field our basic conclusion is that while 2CK physics arises in principle provided the system is sufficiently strongly-correlated, the temperature window over which it could be observed is much lower than is experimentally feasible. This finding disagrees with recent work on the problem, and we explain why. At finite field, we show that the quantum phase transition known to arise at zero-field in the two-impurity Kondo model (2IKM), with an essentially 2CK quantum critical point, persists at finite fields. This raises the prospect of access to 2CK physics by tuning a magnetic field, although preliminary investigation suggests this to be even less feasible than at zero field.