Angle-resolved photoemission spectroscopy study of the topological Kondo insulator candidates CeRhX (X=As, Sb)*

Topological Kondo insulators (TKIs) belong to a class of symmetry-protected topological phases arising from the strong correlation. CeNiSn, CeRhSb, and CeRhAs are known as Kondo insulators with the large anisotropy [1]. Recently CeNiSn and CeRhSb are predicted to be the novel TKIs having the Möbius-twisted surface states [2]. A unique feature in these systems is the non-symmorphic glide and screw axis symmetries, which bring about the new topological surface band structures. We have investigated the electronic structure of CeRhX (X=Sb, As) employing ARPES and DFT/DMFT band calculations. The Fermi surfaces (FSs) and band structures are successfully measured for the three orthogonal crystallographic directions. For X=Sb, the metallic FSs are obtained for all three different planes. Both the FSs obtained at the Ce 4f resonance and the ARPES data are described well by the unfolded DFT FSs and the DMFT band structures, respectively. The temperature-evolution of the Ce 4f peak agrees with that of the Ce 4f Kondo resonance. The photon energy map provides evidence for the 3D character of the Fermi-edge states unlike the theoretically predicted surface states.