Growth and Characterization of Antiferromagnetic Rare-earth Bismuth thin films

Recent studies have shown that Rare-earth Bismuth (RBi) hosts topologically protected Dirac surface states [1,2]. However, spectroscopic measurements on bulk single crystals thus far have been limited to (001) natural cleavage surface of RBi. Here we report the first successful realization and characterization of GdBi (111) films grown on BaF₂ substrates with Molecular Beam Epitaxy. GdBi, in a bulk form, is a semimetal with type-II antiferromagnetic (AFM) order below T_N,bulk = 28 K. With torque magnetometry, we confirm that type-II AFM order is preserved in our films with a Neel temperature T_N,film = 30 K. From electrical transport measurements, we observe a non-linear Hall effect and non-saturating magnetoresistance, the characteristics of a compensated semimetallic electronic structure. Stabilization of GdBi (111) films enables previously unexplored studies of the interplay of symmetry-breaking and Dirac crossings on the (111) surface of RBi. We further anticipate a possible Chern insulator phase in the ultrathin limit, when quantum confinement lifts semimetallicity while retaining non-trivial band topology. Reference: [1] M. Zeng and C. Fang et al., arXiv:1504.03492 (2015), [2] J. Nayak et al., Nat. Comm. 8, 13942 (2017).