Gigantic surface lifetime of an intrinsic topological insulator.


The interaction between light and novel two-dimensional electronic states holds promise to realize new fundamental physics and optical devices. Here, we use pump-probe photoemission spectroscopy to study the optically excited Dirac surface states in the bulk-insulating topological insulator Bi_{2}Te_{2}Se and reveal optical properties that are in sharp contrast to those of bulk-metallic topological insulators. We observe a gigantic optical lifetime exceeding 4  μs (1  μs=10^{-6}  s) for the surface states in Bi_{2}Te_{2}Se, whereas the lifetime in most topological insulators, such as Bi_{2}Se_{3}, has been limited to a few picoseconds (1  ps=10^{-12}  s). Moreover, we discover a surface photovoltage, a shift of the chemical potential of the Dirac surface states, as large as 100 mV. Our results demonstrate a rare platform to study charge excitation and relaxation in energy and momentum space in a two-dimensional system.

DOI: 10.1103/PhysRevLett.115.116801

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@article{Neupane2015GiganticSL, title={Gigantic surface lifetime of an intrinsic topological insulator.}, author={Madhab Neupane and Su-Yang Xu and Yukiaki Ishida and Shuang Jia and Benjamin M. Fregoso and Cheng Chih Liu and Ilya Belopolski and Guang Bian and Nasser Alidoust and Tomasz Durakiewicz and Victor M. Galitski and Shik Shin and Robert Joseph Cava and M Zahid Hasan}, journal={Physical review letters}, year={2015}, volume={115 11}, pages={116801} }