Tuesday, June 11, 2013

1306.2022 (Youhei Yamaji et al.)

Metallic Interface Emerging at Magnetic Domain Wall of Antiferromagnetic
Insulator---Fate of Extinct Weyl Electrons

Youhei Yamaji, Masatoshi Imada
Topological insulators and Chern insulators, in contrast to band insulators, accompany protected metallic surfaces described by Dirac-type fermions. Another peculiar metal with truncated Fermi surface called "arc" is predicted on the surface of zero-gap semiconductors, when Weyl fermions appear in bulk such as in iridium pyrochlore oxides R2Ir2O7 (with rare earth elements R) under a magnetic order. However, the arc on the surface survives only near the all-in/all-out-type antiferromagnetic transition temperature. Here we show that magnetic domain walls realize novel metallic interfaces preserved by zero modes or ingap states with robust arc as a footprint of extinct Weyl electrons even in the seemingly trivial antiferromagnetic insulators. The zero modes follow a one-dimensional Dirac equation that protects ingap states, namely persisting metallicity pinned at domain walls, and maintain a ferromagnetic moment, similarly to spin/charge solitons in polyacetylene. It may solve experimental puzzles of the iridates and offers a novel quantum confinement of electrons enabling magnetic control beyond semiconductor paradigm.
View original: http://arxiv.org/abs/1306.2022

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