Magnetoconductance through a vibrating molecule in the Kondo regime

TL;DR

This paper investigates how magnetic fields influence the conductance of a single-molecule junction in the Kondo regime, revealing different behaviors depending on electron-phonon coupling strength using numerical renormalization group methods.

Contribution

It provides a detailed analysis of magnetic field effects on Kondo resonance in a vibrating molecule, highlighting differences between weak and strong electron-phonon coupling regimes.

Findings

Weak coupling: magnetic field splits Kondo resonance, suppressing conductance.

Strong coupling: charge Kondo effect occurs, resonance is not split, conductance is enhanced.

Magnetic field effects depend critically on electron-phonon interaction strength.

Abstract

The effect of a magnetic field on the equilibrium spectral and transport properties of a single-molecule junction is studied using the numerical renormalization group method. The molecule is described by the Anderson-Holstein model in which a single vibrational mode is coupled to the electron density. The effect of an applied magnetic field on the conductance in the Kondo regime is qualitatively different in the weak and strong electron-phonon coupling regimes. In the former case, the Kondo resonance is split and the conductance is strongly suppressed by a magnetic field $g mu_B B \gtrsim k_BT_K$, with $T_K$ the Kondo temperature. In the strong electron-phonon coupling regime a charge analog of the Kondo effect develops. In this case the Kondo resonance is not split by the field and the conductance in the Kondo regime is enhanced in a broad range of values of $B$.