Iron phthalocyanine on Au(111) is a "non-Landau" Fermi liquid

TL;DR

This paper investigates the non-Landau Fermi liquid behavior in iron phthalocyanine molecules on Au(111), revealing a topological transition in their electronic states influenced by magnetic field and surface interactions.

Contribution

It extends Kondo impurity theory to multi-orbital systems and unifies experimental observations of iron phthalocyanine on Au(111) within this framework.

Findings

Differential conductance shows a zero-bias dip that widens with molecule lifting.

Magnetic field transforms the dip into a peak, indicating a topological transition.

Theoretical model reproduces experimental features and suggests a way to induce the transition.

Abstract

The paradigm of Landau's Fermi liquid theory has been challenged with the finding of a strongly interacting Fermi liquid that cannot be adiabatically connected to a non-interacting system. A spin-1 two-channel Kondo impurity with anisotropy D has a quantum phase transition between two topologically different Fermi liquids with a peak (dip) in the Fermi level for D < Dc (D > Dc). Extending this theory to general multi-orbital problems with finite magnetic field, we reinterpret in a unified and consistent fashion several experimental studies of iron phthalocyanine molecules on Au(111) that were previously described in disconnected and conflicting ways. The differential conductance shows a zero-bias dip that widens when the molecule is lifted from the surface (reducing the Kondo couplings) and is transformed continuously into a peak under an applied magnetic field. We reproduce all features and propose an experiment to induce the topological transition.