Abstract
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 - except for strained HgTe, which has weak inversion asymmetry, a small bulk gap but no bulk charge polarization. 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, 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.
Original language | English |
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Pages (from-to) | 704-708 |
Number of pages | 5 |
Journal | Nature Physics |
Volume | 9 |
Issue number | 11 |
DOIs | |
State | Published - Nov 2013 |
Externally published | Yes |
Funding
We thank Z. Wang and C. X. Liu for the helpful discussion. Y.L.C. acknowledges support from a DARPA MESO project (No. N66001-11-1-4105) and the EPSRC First Grant (EP/K04074X/1). B.Z., Z.K.L., Z.X.S. and X.L.Q. acknowledge support from Department of Energy, Office of Basic Energy Science (contract DE-AC02-76SF00515). T.S. acknowledges support from MEXT, Japan (Grant-in-Aid for Scientific Research (B), No. 24340078). H.J.Z. acknowledges support from the Army Research Office (No. W911NF-09-1-0508). J.A.S. acknowledges support from the Stanford Graduate Fellowship. D.L. acknowledges the Swiss National Science Foundation.