Abstract
Through a combination of experimental techniques we show that the topmost layer of the topological insulator TlBiSe2 as prepared by cleavage is formed by irregularly shaped Tl islands at cryogenic temperatures and by mobile Tl atoms at room temperature. No trivial surface states are observed in photoemission at low temperatures, which suggests that these islands cannot be regarded as a clear surface termination. The topological surface state is, however, clearly resolved in photoemission experiments. This is interpreted as direct evidence of its topological self-protection and shows the robust nature of the Dirac cone-like surface state. Our results can also help explain the apparent mass acquisition in S-doped TlBiSe2.
Highlights
Topological insulators (TIs) constitute a novel class of materials that has received a large amount of attention over recent years [1, 2]
In order to obtain a better understanding of the surface termination and to understand why the topologically trivial surface states could be missing in the angle-resolved photoemission (ARPES) data, we performed scanning tunneling microscopy (STM) experiments on the same batch of samples
In our STM measurements at different bias voltages we see no evidence of any dispersive electronic states within the worms, but it should be noted that based on these measurements alone we cannot exclude the presence of such states
Summary
Topological insulators (TIs) constitute a novel class of materials that has received a large amount of attention over recent years [1, 2]. Within a simplified model it is often suggested that this protection is caused by the spin structure which suppresses backscattering events as this would require a highly improbable spin flip [2] This simplification is certainly valid for the one-dimensional edge states of two-dimensional (2D) TIs [7], the additional phase-space available for scattering for the 2D surface states of 3D TIs calls for a protection mechanism different from avoided backscattering. Later theoretical considerations verified this behaviour and suggested that the state moved to the quintuple layer [12] This indicates that the real protection mechanism of the TSS is, just like its unique spin structure, a consequence of the transition between phases of different topology at the edge of a TI [1]
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