Temperature-dependent angle-resolved photoemission spectroscopy study of the Ce 4f states in a possible topological Kondo insulator CeRhAs

Abstract

The electronic structure of a possible topological Kondo insulator of CeRhAs has been investigated by employing temperature $(T)$-dependent angle-resolved photoemission spectroscopy (ARPES). Fermi surfaces (FSs) and band structures are successfully measured for three orthogonal crystallographic planes. The measured Fermi-edge states are found to have a three-dimensional (3D) character, contradictory to the proposed topological surface states of the $2\text{D}$ character. The measured FSs due to the Ce $4f$ electrons agree well with those from the density functional theory band structures unfolded into the reduced Ce-only unit cell. The theoretically predicted hourglass-type bulk bands along $\overline{X}\overline{S}\overline{X}$ are not clearly resolved, in spite of the evident existence of those band features. $T$-dependent ARPES measurements reveal that the coherent Ce $4f$ states, having two pseudogap structures of ${\mathrm{\ensuremath{\Delta}}}_{1}\ensuremath{\sim}80$ meV and ${\mathrm{\ensuremath{\Delta}}}_{2}\ensuremath{\sim}30$ meV, persist to remain above 200 K, in agreement with the high Kondo temperature of CeRhAs.