Anomalous temperature and symmetry-dependent electronic excitations in GdB6

Highlights: • Unique electronic light scattering in rare-earth boride is observed. • Clear effects of electron-phonon interaction in the spectra temperature behavior. • Ab initio electron structure calculation doesn't explain temperature effects. • Extra electron scattering is proposed to be coupled to spin disorder. • Chiral excitations found may confirm spin fluctuations existence. -- Abstract: Electronic Raman scattering was studied on GdB₆ single crystals in the temperature range 10–500 K. The shapes and energy positions of all electronic continua depend on the temperature and symmetry of the excitations. The experimental spectra were modeled using the ab initio DFT electronic structure calculations, taking into account electron-phonon scattering. The appearance of continua of the A_1g and E_g symmetry in the spectra was identified with inelastic light scattering from electronic intraband excitations renormalized by the lattice and spin disorder scattering, which is confirmed by the performed calculations. Unexpected observation of T_1g symmetry excitations whose profile, intensity and temperature dependence coincide with those for the T_2g symmetry excitations suggests the existence of scattering by spin density fluctuations.