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arXiv · 1206.0278

Dirac point spectral weight suppression and surface "gaps" in nonmagnetic and magnetic topological insulators

Su-Yang Xu·L. A. Wray·N. Alidoust·Y. Xia·M. Neupane·Chang Liu·H. -W. Ji·S. Jia·R. J. Cava·M. Z. Hasan
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Abstract

It is predicted that electrons on the surface of a topological insulator can acquire a mass (massive Dirac fermion) by opening up a gap at the Dirac point when time-reversal symmetry is broken via the out-of-plane magnetization. We report photoemission studies on a series of topological insulator materials focusing on the spectral behavior in the vicinity of the Dirac node. Our results show that the spectral intensity is suppressed resulting in a "gap"-like feature in materials with or without any magnetic impurity or doping. The Zeeman gap in magnetically doped samples, expected to be rather small, is likely masked by the non-magnetic strong spectral weight suppression involving a large energy scale we report. The photoemission spectral weight suppression observed around the Dirac node thus cannot be taken as the sole evidence for a time-reversal symmetry breaking magnetic gap. We discuss a few possible extrinsic and kinematic origins of the Dirac point spectral weight suppression ("gap") observed in many commonly studied topological materials.

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Su-Yang Xu, L. A. Wray, N. Alidoust, Y. Xia, M. Neupane, Chang Liu, H. -W. Ji, S. Jia, R. J. Cava, M. Z. Hasan. 2012-12-14. Dirac point spectral weight suppression and surface "gaps" in nonmagnetic and magnetic topological insulators. https://arxiv.org/abs/1206.0278

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