Semimetallic Nature and Magnetic Polarons in EuB6 Studied by Angle-Resolved Photoemission Spectroscopy

TL;DR

This study uses ARPES to reveal EuB6's semimetallic nature, magnetic interactions, and evidence of magnetic polarons, enhancing understanding of its electronic and magnetic properties.

Contribution

First ARPES investigation showing the semimetallic band structure and magnetic polaron formation in EuB6, supported by Monte Carlo simulations.

Findings

EuB6 is a semimetal with a B 2p hole pocket at the X point.

Exchange splitting of B 2p bands decreases with temperature and vanishes above TC.

Magnetic polarons are supported by ARPES data and Monte Carlo simulations.

Abstract

Temperature-dependent angle-resolved photoemission spectroscopy (ARPES) was carried out on single-crystalline EuB6 samples. By measuring ARPES spectra in an extended Brillouin zone, a B 2p hole pocket centered at the X point is clearly observed, thus proving the semimetallic nature of EuB6. Below the Curie temperature TC, ARPES spectra show two B 2p bands of which separation is due to an exchange interaction between local Eu 4f and itinerant B 2p electrons. The exchange splitting becomes smaller as the temperature increases and disappears well above TC. Additionally, a diffuse structure near the Fermi level survives just above TC. Such behavior is well described by Monte Carlo simulations of a Kondo lattice model, thus supporting the formation of magnetic polarons in EuB6, which accounts for the resistivity upturn near above TC when lowering the temperature.