Anisotropic Zeeman Splitting in YbNi4P2

TL;DR

This study investigates Lifshitz transitions in the heavy-fermion compound YbNi4P2 under high magnetic fields, revealing anisotropic Zeeman effects and insights into the Fermi surface and quasiparticle coherence.

Contribution

It provides the first detailed angular dependence analysis of Lifshitz transitions in YbNi4P2, demonstrating anisotropic Zeeman splitting consistent with a crystal field model.

Findings

Lifshitz transitions follow a Zeeman-shift model with anisotropic g-factor.

The anisotropy of the g-factor is approximately 3.8.

The results support the coherent nature of heavy quasiparticles.

Abstract

The electronic structure of heavy-fermion materials is highly renormalised at low temperatures with localised moments contributing to the electronic excitation spectrum via the Kondo effect. Thus, heavy-fermion materials are very susceptible to Lifshitz transitions due to the small effective Fermi energy arising on parts of the renormalised Fermi surface. Here, we study Lifshitz transitions that have been discovered in YbNi4P2 in high magnetic fields. We measure the angular dependence of the critical fields necessary to induce a number of Lifshitz transitions and find it to follow a simple Zeeman-shift model with anisotropic g-factor. This highlights the coherent nature of the heavy quasiparticles forming a renormalised Fermi surface. We extract information on the orientation of the Fermi surface parts giving rise to the Lifshitz transitions and we determine the anisotropy of the effective g-factor to be $\eta \approx 3.8$ in good agreement with the crystal field scheme of YbNi4P2.