By employing angle-resolved photoemission spectroscopy combined with first-principles calculations, we performed a systematic investigation on the electronic structure of LaBi, which exhibits extremely large magnetoresistance (XMR), and is theoretically predicted to possess band anticrossing with nontrivial topological properties. Here, the observations of the Fermi-surface topology and band dispersions are similar to previous studies on LaSb [Phys. Rev. Lett. 117, 127204 (2016)], a topologically trivial XMR semimetal, except the existence of a band inversion along the Γ-X direction, with one massless and one gapped Dirac-like surface state at the X and Γ points, respectively. The odd number of massless Dirac cones suggests that LaBi is analogous to the time-reversal Z2 nontrivial topological insulator. These findings open up a new series for exploring novel topological states and investigating their evolution from the perspective of topological phase transition within the family of rare-earth monopnictides.
@article{arxiv.1612.03589,
title = {Evidence of topological insulator state in the semimetal LaBi},
author = {R. Lou and B. -B. Fu and Q. N. Xu and P. -J. Guo and L. -Y. Kong and L. -K. Zeng and J. -Z. Ma and P. Richard and C. Fang and Y. -B. Huang and S. -S. Sun and Q. Wang and L. Wang and Y. -G. Shi and H. C. Lei and K. Liu and H. M. Weng and T. Qian and H. Ding and S. -C. Wang},
journal= {arXiv preprint arXiv:1612.03589},
year = {2017}
}