Optically detecting the edge-state of a three-dimensional topological insulator under ambient conditions by ultrafast infrared photoluminescence spectroscopy.

Shun-Ya Maezawa,Tohru Suemoto,Kenta Kuroda,Takashi Someya,Hiroshi Watanabe,Iwao Matsuda,Masahiro Takeda

doi:10.1038/srep16443

Shun-Ya Maezawa, Tohru Suemoto + Show 5 more

Open Access

https://doi.org/10.1038/srep16443

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Journal: Scientific Reports	Publication Date: Nov 10, 2015
Citations: 4	License type: CC BY 4.0

Affiliation: The University of Tokyo

Abstract

Ultrafast infrared photoluminescence spectroscopy was applied to a three-dimensional topological insulator TlBiSe2 under ambient conditions. The dynamics of the luminescence exhibited bulk-insulating and gapless characteristics bounded by the bulk band gap energy. The existence of the topologically protected surface state and the picosecond-order relaxation time of the surface carriers, which was distinguishable from the bulk response, were observed. Our results provide a practical method applicable to topological insulators under ambient conditions for device applications.

Highlights

Detection in the visible to infrared regions
We report the application of the infrared TrPLS technique to a topological insulators (TIs), TlBiSe2, under ambient conditions (Fig. 1a)
The decay time evaluated with a single exponential fitting for each curve and the peak position time, which is a measure of the rise time, are shown as functions of photon energy in the inset of Fig. 2a

Summary

Introduction

Detection in the visible to infrared regions. TrPLS is expected to be a practical approach to investigating the surface carrier dynamics in TIs20 under the ambient condition; no TI research with TrPLS has been reported, to the best of our knowledge. Tl1−x Bi1+x Se2 (x = 0 .025) was studied, where the Fermi level is located near the Dirac point[24,25], as shown, resulting in a low intrinsic carrier concentration in the bulk conduction and valence bands. The infrared time-resolved luminescence on the order of sub- to several picoseconds from the TlBiSe2 crystal was observed. At photon energies below the bulk band gap energy, the luminescence showed behavior characteristic to the gapless surface state, as distinguished from the semiconductor-like behavior above the gap energy. This observation clearly indicates the existence of the topologically protected surface state under ambient conditions

Methods

Results

Conclusion