Observation of three-dimensional bulk Fermi surfaces for a strongly correlated material by soft x-ray $h\nu$-dependent (700-860 eV) ARPES

TL;DR

This study used soft x-ray ARPES to map the three-dimensional Fermi surfaces of CeRu$_2$Ge$_2$ in its paramagnetic phase, revealing both consistencies and discrepancies with theoretical models and prior measurements, highlighting changes across magnetic phases.

Contribution

First detailed 3D Fermi surface mapping of CeRu$_2$Ge$_2$ using soft x-ray ARPES in the paramagnetic phase, showing phase-dependent changes in 4f electron contributions.

Findings

Fermi surfaces partly match localized 4f band-structure calculations.

Discrepancies observed between ARPES and de Haas-van Alphen measurements.

Indication of fundamental changes in 4f contributions across magnetic phase transition.

Abstract

Three-dimensional Fermi surfaces at a high temperature have been clarified for a strongly correlated Ce compound, ferromagnet CeRu$_2$Ge$_2$ in the paramagnetic phase, by virtue of a soft x-ray $h\nu$-dependent (700-860 eV) ARPES. Although the observed Fermi surfaces as well as quasiparticle dispersions are partly explained by a band-structure calculation based on a localized $4f$ model, qualitative discrepancy in experiments, between our APRES in the paramagnetic phase and de Haas-van Alphen measurement in the ferromagnetic phase, is revealed. This suggests a fundamental change in the $4f$ contribution to the Fermi surfaces across the magnetic phase transition widely seen for Ce compounds.