Spectroscopic Evidence for Electron-Boson Coupling in Half-metallic CrO2

Abstract

We report quasiparticle properties of the half-metal ferromagnet CrO2 by means of high-resolution angle-resolved photoemission spectroscopy (ARPES). We clearly observed the Fermi surface (FS) and band dispersion in good agreement with the previous reports. Moreover, the ARPES band dispersion reveals a distinct kink structure around 68 meV, providing the first spectroscopic evidence for the elementary excitations in CrO2. The energy scale of this feature is comparable to the Debye temperature and the $A\subm{1g}$ phonon mode, suggesting the electron-phonon interaction. From the detailed analysis, we have extracted the self-energy and found two characteristic structures in the real part of the self-energy. Assuming the existence of the electron-magnon interaction as well as the electron-phonon interaction, we could reproduce the evaluated real and imaginary parts of the self-energy as well as ARPES intensity. Our findings reveal the renormalized quasiparticle (QP) dynamics in CrO$_2$ and provide valuable insights into the fundamental many-body interactions governing half-metallic ferromagnets.