Magnetic Field Effects on Quasiparticles in Strongly Correlated Local Systems

TL;DR

This paper develops a method to describe quasiparticles in strongly correlated systems under magnetic fields using field-dependent parameters, demonstrated through the Anderson impurity model and NRG calculations, revealing how quasiparticles evolve with field strength.

Contribution

It introduces a framework for describing magnetic field effects on quasiparticles in strongly correlated systems using renormalized parameters and NRG, providing detailed insights into their evolution.

Findings

Quasiparticles can be described by field-dependent parameters.

NRG calculations reveal how quasiparticle properties change with magnetic field.

The approach allows calculation of low-temperature conductivity in arbitrary magnetic fields.

Abstract

We show that quasiparticles in a magnetic field of arbitrary strength $H$ can be described by field dependent parameters. We illustrate this approach in the case of an Anderson impurity model and use the numerical renormalization group (NRG) to calculate the renormalized parameters for the levels with spin $\sigma$, $\tilde\epsilon_{\mathrm{d},\sigma}(H)$, resonance width $\tilde\Delta(H)$ and the effective local quasiparticle interaction $\tilde U(H)$. In the Kondo or strong correlation limit of the model the progressive de-renormalization of the quasiparticles can be followed as the magnetic field is increased. The low temperature behaviour, including the conductivity, in arbitrary magnetic field can be calculated in terms of the field dependent parameters using the renormalized perturbation expansion. Using the NRG the field dependence of the spectral density on higher scales is also calculated.