Universality and scaling in a charge two-channel Kondo device

TL;DR

This paper demonstrates that a charge two-channel Kondo device can be accurately simulated both universally and nonuniversally, with numerical and analytical results matching experimental data over a wide range, revealing detailed RG flow and conductance behavior.

Contribution

The study provides a comprehensive numerical and analytical analysis of a charge two-channel Kondo model, closely matching experimental results and exploring nonuniversal effects beyond the scaling limit.

Findings

Quantitative reproduction of experimental conductance curves over 9 orders of magnitude.

Identification of RG flow to a critical point involving a free Majorana fermion.

Analytic predictions for non-linear conductance away from thermal equilibrium.

Abstract

We study a charge two-channel Kondo model, demonstrating that recent experiments [Iftikhar et al, Nature 526, 233 (2015)] realize an essentially perfect quantum simulation -- not just of its universal physics, but also nonuniversal effects away from the scaling limit. Numerical renormalization group (NRG) calculations yield conductance lineshapes encoding RG flow to a critical point involving a free Majorana fermion. By mimicking the experimental protocol, the experimental curve is reproduced quantitatively over 9 orders of magnitude, although we show that far greater bandwidth/temperature separation is required to obtain the universal result. Fermi liquid instabilities are also studied: In particular, our exact analytic results for non-linear conductance provide predictions away from thermal equilibrium, in the regime of existing experiments.