Conductance of Quantum Impurity Models from Quantum Monte Carlo

TL;DR

This paper demonstrates that a world-line quantum Monte Carlo method can accurately compute the conductance of quantum impurity models at low temperatures, providing a reliable alternative to numerical renormalization group techniques.

Contribution

The paper introduces a QMC-based approach to calculate conductance in Anderson impurity models and compares its accuracy with NRG results across different regimes.

Findings

Excellent agreement with NRG at low temperatures

Method unreliable at higher temperatures

Effective for mixed valence and Kondo regimes

Abstract

The conductance of two Anderson impurity models, one with two-fold and another with four-fold degeneracy, representing two types of quantum dots, is calculated using a world-line quantum Monte Carlo (QMC) method. Extrapolation of the imaginary time QMC data to zero frequency yields the linear conductance, which is then compared to numerical renormalization group results in order to assess its accuracy. We find that the method gives excellent results at low temperature (T<Tk) throughout the mixed valence and Kondo regimes, but it is unreliable for higher temperature.