Absence of a Dirac gap in ferromagnetic Cr$_x$(Bi$_{0.1}$Sb$_{0.9}$)$_{2-x}$Te$_3$

Chung Koo Kim; Jonathan D. Denlinger; Asish K. Kundu; Genda Gu; Tonica Valla

doi:10.1063/5.0039059

paper

Absence of a Dirac gap in ferromagnetic Cr $_{x}$ (Bi $_{0.1}$ Sb $_{0.9}$ ) $_{2 - x}$ Te $_{3}$

arXiv:2012.05884 · doi:10.1063/5.0039059

Abstract

Magnetism breaks the time reversal symmetry expected to open a Dirac gap in 3D topological insulators that consequently leads to quantum anomalous Hall effect. The most common approach of inducing ferromagnetic state is by doping magnetic 3 $d$ elements into bulk of 3D topological insulators. In Cr $_{0.15}$ (Bi $_{0.1}$ Sb $_{0.9}$ ) $_{1.85}$ Te $_{3}$ , the material where the quantum anomalous Hall effect was initially discovered at temperatures much lower than the ferromagnetic transition, $T_{C}$ , the scanning tunneling microscopy studies have reported a large Dirac gap $\sim 20 - 100$ meV. The discrepancy between the low temperature of quantum anomalous Hall effect ( $≪ T_{C}$ ) and large spectroscopic Dirac gaps ( $≫ T_{C}$ ) found in magnetic topological insulators remains puzzling. Here, we used angle-resolved photoemission spectroscopy to study the surface electronic structure of pristine and potassium doped surface of Cr $_{0.15}$ (Bi $_{0.1}$ Sb $_{0.9}$ ) $_{1.85}$ Te $_{3}$ . Upon potassium deposition, the $p$ -type surface state of pristine sample was turned into an $n$ -type, allowing spectroscopic observation of Dirac point. We find a gapless surface state, with no evidence of a large Dirac gap reported in tunneling studies.

7 pages, 3 figures

Absence of a Dirac gap in ferromagnetic Crx​(Bi0.1​Sb0.9​)2−x​Te3​

Abstract

References in corpus (6)

Absence of a Dirac gap in ferromagnetic Cr $_{x}$ (Bi $_{0.1}$ Sb $_{0.9}$ ) $_{2 - x}$ Te $_{3}$