Quantum Critical Points in Quantum Impurity Systems

TL;DR

This paper uses the numerical renormalization group to study zero-temperature quantum phase transitions in impurity systems, revealing critical points that cannot be described by non-interacting excitations.

Contribution

It provides a detailed analysis of quantum critical points in the soft-gap Anderson model, highlighting their non-trivial nature beyond non-interacting theories.

Findings

Identification of quantum critical points with non-trivial fixed points

Demonstration that critical points cannot be described by non-interacting particles

Analysis of phase transitions in impurity systems

Abstract

The numerical renormalization group method is used to investigate zero temperature phase transitions in quantum impurity systems, in particular in the soft-gap Anderson model, where an impurity couples to a non-trivial fermionic bath. In this case, zero temperature phase transitions occur between two different phases whose fixed points can be built up of non-interacting single-particle states. However, the quantum critical point cannot be described by non-interacting fermionic or bosonic excitations.