Topological surface states in the Kondo insulator YbB₁₂revealed via planar tunneling spectroscopy

Planar tunnelling spectroscopy of the Kondo insulator (KI) SmB₆ suggests that an interaction between surface Dirac fermions and bulk spin excitons results in incompletely protected topological surface states (TSS) [1]. Studying new topological KIs to gain further insight into the true nature of TSS in these compounds is necessary. Band calculations predict that the KI YbB₁₂ hosts TSS protected by crystalline mirror symmetry [2]. Here we present tunneling conductance spectra obtained from the (001) surface of YbB₁₂ single crystals and discuss them in comparison to SmB₆ [1]. The linear conductance at low bias provides strong evidence for the existence of surface Dirac fermions and the double-hump structure in the negative bias region is associated with hybridized band edges, in agreement with the theory [2]. Although these similarities with SmB₆ are suggestive of the existence of TSS in YbB₁₂ in agreement with other experiments [3], we also discuss the detailed discrepancy attesting that the exact nature of its TSS is different from SmB₆.



[1] W. K. Park et al., Proc. Natl. Acad. Sci. U.S.A. 113, 6599 (2016); W. K. Park et al., Phys. Rev. B 103, 155125 (2021)

[2] H. Weng et al., PRL 112, 016403 (2014).

[3] Y. Sato et al., J. Phys. D: Appl. Phys. 54, 404002 (2021).