Discovery of a single topological Dirac fermion in the strong inversion asymmetric compound BiTeCl

Author List: Chen, YL (Chen, Y. L.)[ 1,2,3 ] ; Kanou, M (Kanou, M.)[ 4 ] ; Liu, ZK (Liu, Z. K.)[ 5,6 ] ; Zhang, HJ (Zhang, H. J.)[ 5,6 ] ; Sobota, JA (Sobota, J. A.)[ 3,5,6 ] ; Leuenberger, D (Leuenberger, D.)[ 3,5,6 ] ; Mo, SK (Mo, S. K.)[ 7 ] ; Zhou, B (Zhou, B.)[ 1,7 ] ; Yang, SL (Yang, S-L.)[ 3,5,6 ] ; Kirchmann, PS (Kirchmann, P. S.)[ 3 ] ; Lu, DH (Lu, D. H.)[ 8 ] ; Moore, RG (Moore, R. G.)[ 3 ] ; Hussain, Z (Hussain, Z.)[ 7 ] ; Shen, ZX (Shen, Z. X.)[ 3,5,6 ] ; Qi, XL (Qi, X. L.)[ 5,6 ] ; Sasagawa, T (Sasagawa, T.)[ 4 ]

Journal Reference: Nature Physics, Vol: 9, Issue: 11, Pages: 704-708, DOI: 10.1038/NPHYS2768, Published: Nov 2013

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In the past few years, a new state of quantum matter known as the time-reversal-invariant topological insulator has been predicted theoretically and realized experimentally. All of the topological insulators discovered so far in experiment are inversion symmetric(1-5)-except for strained HgTe, which has weak inversion asymmetry, a small bulk gap but no bulk charge polarization(6). Strong inversion asymmetry in topological insulators would not only lead to many interesting phenomena, such as crystalline-surface-dependent topological electronic states, pyroelectricity and intrinsic topological p-n junctions, but would also serve as an ideal platform for the realization of topological magneto-electric effects(7,8), which result from the modification of Maxwell equations in topological insulators. Here we report the discovery of a strong inversion asymmetric topological insulator phase in BiTeCl by angle-resolved photoemission spectroscopy, which reveals Dirac surface states and crystalline-surface-dependent electronic structures. Moreover, we observe a tenfold increase of the bulk energy gap in BiTeCl over the weak inversion asymmetric topological insulator HgTe, making it a promising platform for topological phenomena and possible applications at high temperature.

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