Discovery of a single topological Dirac fermion in the strong inversion asymmetric compound BiTeCl
Discovery of a single topological Dirac fermion in the strong inversion asymmetric compound BiTeCl
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DOI：
10.1038/nphys2768
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发表时间：
2013-11-01
期刊：
影响因子：
19.6
通讯作者：
Sasagawa, T.
中科院分区：
文献类型：
--
作者：
Chen, Y. L.;Kanou, M.;Sasagawa, T.
在过去的几年里，人们从理论上预言并在实验上实现了一种新的量子态，即时间反转不变的拓扑绝缘体。到目前为止，实验中发现的所有拓扑绝缘体都是反转对称的(1-5)--除了应变HgTe，它具有弱的反转不对称性，体隙小，但没有体电荷极化(6)。拓扑绝缘体的强反转不对称性不仅会导致许多有趣的现象，如依赖于晶面的拓扑电子态、热释电和本征拓扑p-n结，而且还将成为实现拓扑磁电效应(7，8)的理想平台，这些效应是由拓扑绝缘体中的Maxwell方程修正而来的。本文报道了用角度分辨光电子能谱在BiTeCl中发现了一个强反转的不对称拓扑绝缘体相，揭示了Dirac表面态和晶面依赖的电子结构。此外，我们观察到BiTeCl的体能隙比弱反转非对称拓扑绝缘体HgTe增加了10倍，这使其成为研究高温拓扑现象和可能应用的平台。
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.