Antiferromagnetic topological insulator with selectively gapped Dirac cones

Abstract

Antiferromagnetic (AF) topological materials offer a fertile ground to explore a variety of quantum phenomena such as axion magnetoelectric dynamics and chiral Majorana fermions. To realize such intriguing states, it is essential to establish a direct link between electronic states and topology in the AF phase, whereas this has been challenging because of the lack of a suitable materials platform. Here we report the experimental realization of the AF topological-insulator phase in NdBi. By using micro-focused angle-resolved photoemission spectroscopy, we discovered contrasting surface electronic states for two types of AF domains; the surface having the out-of-plane component in the AF-ordering vector displays Dirac-cone states with a gigantic energy gap, whereas the surface parallel to the AF-ordering vector hosts gapless Dirac states despite the time-reversal-symmetry breaking. The present results establish an essential role of combined symmetry to protect massless Dirac fermions under the presence of AF order and widen opportunities to realize exotic phenomena utilizing AF topological materials.

arXiv comment28 pages, 12 figures

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Cited by in corpus (6)

• Observation of spin splitting in the surface electronic structure of antiferromagnet NdBi
• Unexpected changes in the band structure within AFM1 state of CeBi
• Long-range magnetic order induced surface state in GdBi and DyBi
• Unconventional band splitting of CeSb in the devil's staircase transition
• Universal Role of Combined Symmetry for the Protection of the Dirac Cone in Antiferromagnetic Topological Insulators
• Magnetic structure of EuZn${}_2$Sb${}_2$ single-crystal thin-film