Kondo model for the "0.7 anomaly" in transport through a quantum point contact

TL;DR

This paper models the 0.7 conductance anomaly in quantum point contacts using a Kondo effect framework, explaining experimental features and predicting spin-polarized currents under magnetic fields.

Contribution

It introduces an Anderson model analysis of the 0.7 anomaly in quantum point contacts, highlighting the role of valence-dependent hybridization and Kondo physics.

Findings

High residual conductance above Kondo temperature explained

Abrupt energy-dependent hybridization influences conductance

Predicted spin-polarized current under magnetic field

Abstract

Experiments on quantum point contacts have highlighted an anomalous conductance plateau at $0.7 (2e^2/h)$, with features suggestive of the Kondo effect. Here we present an Anderson model for transport through a point contact which we analyze in the Kondo limit. Hybridization to the band increases abruptly with energy but decreases with valence, so that the background conductance and the Kondo temperature $T_K$ are dominated by different valence transitions. This accounts for the high residual conductance above $T_K$. A spin-polarized current is predicted for Zeeman splitting $g^* \mu_B B > k_B T_K,k_BT$.