Functional Renormalization Group treatment of the 0.7-analog in quantum point contacts

TL;DR

This paper applies an advanced functional renormalization group method to analyze the 0.7-analog phenomenon in quantum point contacts, successfully reproducing experimental conductance features and explaining their magnetic field dependence.

Contribution

It introduces an extended Coupled-Ladder Approximation fRG approach to study the 0.7-analog, providing new insights into its magnetic field dependence and underlying physics.

Findings

Reproduces the magnetic field dependence of conductance at the 0.7-analog

Shows the dependence varies depending on whether the analog is approached from higher or lower fields

Explains the effect qualitatively with a simple Hartree picture

Abstract

We use a recently developed fRG method (extendend Coupled-Ladder Approximation) to study the 0.7-analog in quantum point contacts, arising at the crossing of the 1st and 2nd band at suf- ficiently high magnetic fields. We reproduce the main features of the experimentally observed magnetic field dependence of the conductance at the 0.7-analog, using a QPC model with two bands and short-range interactions. In particular, we reproduce the fact that this dependence is quali- tatively different, depending on whether the analog is approached from higher or lower magnetic fields. We show that this effect can be explained qualitatively within a simple Hartree picture for the influence of the lowest electrons.