Climbing the Entropy Barrier: Driving the Single- towards the Multichannel Kondo Effect by a Weak Coulomb Blockade of the Leads

TL;DR

This paper investigates how weak Coulomb blockade effects in quantum dot systems can destabilize the single-channel Kondo effect, leading to a flow towards a multi-channel Kondo fixed point with unique thermodynamic properties.

Contribution

It introduces a model showing that small charging energies can induce a transition from single- to multi-channel Kondo effects, revealing new nonlocal interaction physics.

Findings

Long-ranged interactions destabilize the single-channel Kondo effect.

Flow towards a multi-channel Kondo fixed point occurs even with small charging energy.

Predicted transport properties and impurity entropy behavior.

Abstract

We study a model proposed recently in which a small quantum dot is coupled symmetrically to several large quantum dots characterized by a charging energy E_c. Even if E_c is much smaller than the Kondo temperature T_K, the long-ranged interactions destabilize the single-channel Kondo effect and induce a flow towards a multi-channel Kondo fixed point associated with a rise of the impurity entropy with decreasing temperature. Such an ``uphill flow'' implies a negative impurity specific heat, in contrast to all systems with local interactions. An exact solution found for a large number of channels allows us to capture this physics and to predict transport properties.