Time-resolved THz dynamics in thin films of Bi2Se3

R. Valdes Aguilar; J. Qi; M. Brahlek; N. Bansal; A. Azad; S. Oh; A. J. Taylor; R. P. Prasankumar; D. A. Yarotski

doi:10.1109/IRMMW-THz.2014.6956063

Time-resolved THz dynamics in thin films of Bi₂Se₃

R. Valdes Aguilar, J. Qi, M. Brahlek, N. Bansal, A. Azad, S. Oh, A. J. Taylor, R. P. Prasankumar, D. A. Yarotski

School of Arts and Sciences, New High Energy Theory Center

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

Abstract

Topological insulators represent a new state of matter where bulk insulators exhibit metallic surfaces that are protected by time reversal symmetry. However, in common transport measurements residual bulk conductivity hinders the properties of the topologically protected surfaces. Alternatively, terahertz spectroscopy has recently been shown to be capable of discerning the bulk and surface carrier conductivity. Here we use time-resolved optical pump-THz probe spectroscopy at low temperatures to study the hot carrier response of thin films of Bi₂Se₃ of several thicknesses and separate the bulk from the surface response. We find that for thinner films the photo excitation changes the transport scattering rate and reduces the surface conductivity. For thicker films, this process competes with the photoinduced increase in bulk conductivity, which occurs on shorter timescales and scales with the increase in both the film thickness and optical excitation fluence. These different dynamics of the surface and bulk electrons indicate a decoupling of surface and bulk carriers, and present the possibility of accessing long-lived surface photo-carriers for optoelectronic applications.

Original language	English (US)
Title of host publication	2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2014
Publisher	IEEE Computer Society
ISBN (Electronic)	9781479938773
DOIs	https://doi.org/10.1109/IRMMW-THz.2014.6956063
State	Published - Nov 13 2014
Event	39th International Conference on Infrared, Millimeter and Terahertz Waves, IRMMW-THz 2014 - Tucson, United States Duration: Sep 14 2014 → Sep 19 2014

Publication series

Name	International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz
ISSN (Print)	2162-2027
ISSN (Electronic)	2162-2035

Other

Other	39th International Conference on Infrared, Millimeter and Terahertz Waves, IRMMW-THz 2014
Country/Territory	United States
City	Tucson
Period	9/14/14 → 9/19/14

All Science Journal Classification (ASJC) codes

Energy Engineering and Power Technology
Electrical and Electronic Engineering

Access to Document

10.1109/IRMMW-THz.2014.6956063

Cite this

Aguilar, R. V., Qi, J., Brahlek, M., Bansal, N., Azad, A., Oh, S., Taylor, A. J., Prasankumar, R. P., & Yarotski, D. A. (2014). Time-resolved THz dynamics in thin films of Bi₂Se₃. In 2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2014 Article 6956063 (International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz). IEEE Computer Society. https://doi.org/10.1109/IRMMW-THz.2014.6956063

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title = "Time-resolved THz dynamics in thin films of Bi2Se3",

abstract = "Topological insulators represent a new state of matter where bulk insulators exhibit metallic surfaces that are protected by time reversal symmetry. However, in common transport measurements residual bulk conductivity hinders the properties of the topologically protected surfaces. Alternatively, terahertz spectroscopy has recently been shown to be capable of discerning the bulk and surface carrier conductivity. Here we use time-resolved optical pump-THz probe spectroscopy at low temperatures to study the hot carrier response of thin films of Bi2Se3 of several thicknesses and separate the bulk from the surface response. We find that for thinner films the photo excitation changes the transport scattering rate and reduces the surface conductivity. For thicker films, this process competes with the photoinduced increase in bulk conductivity, which occurs on shorter timescales and scales with the increase in both the film thickness and optical excitation fluence. These different dynamics of the surface and bulk electrons indicate a decoupling of surface and bulk carriers, and present the possibility of accessing long-lived surface photo-carriers for optoelectronic applications.",

author = "Aguilar, {R. Valdes} and J. Qi and M. Brahlek and N. Bansal and A. Azad and S. Oh and Taylor, {A. J.} and Prasankumar, {R. P.} and Yarotski, {D. A.}",

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year = "2014",

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doi = "10.1109/IRMMW-THz.2014.6956063",

language = "English (US)",

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Aguilar, RV, Qi, J, Brahlek, M, Bansal, N, Azad, A, Oh, S, Taylor, AJ, Prasankumar, RP & Yarotski, DA 2014, Time-resolved THz dynamics in thin films of Bi₂Se₃. in 2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2014., 6956063, International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, IEEE Computer Society, 39th International Conference on Infrared, Millimeter and Terahertz Waves, IRMMW-THz 2014, Tucson, United States, 9/14/14. https://doi.org/10.1109/IRMMW-THz.2014.6956063

Time-resolved THz dynamics in thin films of Bi₂Se₃. / Aguilar, R. Valdes; Qi, J.; Brahlek, M. et al.
2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2014. IEEE Computer Society, 2014. 6956063 (International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

TY - GEN

T1 - Time-resolved THz dynamics in thin films of Bi2Se3

AU - Aguilar, R. Valdes

AU - Qi, J.

AU - Brahlek, M.

AU - Bansal, N.

AU - Azad, A.

AU - Oh, S.

AU - Taylor, A. J.

AU - Prasankumar, R. P.

AU - Yarotski, D. A.

PY - 2014/11/13

Y1 - 2014/11/13

N2 - Topological insulators represent a new state of matter where bulk insulators exhibit metallic surfaces that are protected by time reversal symmetry. However, in common transport measurements residual bulk conductivity hinders the properties of the topologically protected surfaces. Alternatively, terahertz spectroscopy has recently been shown to be capable of discerning the bulk and surface carrier conductivity. Here we use time-resolved optical pump-THz probe spectroscopy at low temperatures to study the hot carrier response of thin films of Bi2Se3 of several thicknesses and separate the bulk from the surface response. We find that for thinner films the photo excitation changes the transport scattering rate and reduces the surface conductivity. For thicker films, this process competes with the photoinduced increase in bulk conductivity, which occurs on shorter timescales and scales with the increase in both the film thickness and optical excitation fluence. These different dynamics of the surface and bulk electrons indicate a decoupling of surface and bulk carriers, and present the possibility of accessing long-lived surface photo-carriers for optoelectronic applications.

AB - Topological insulators represent a new state of matter where bulk insulators exhibit metallic surfaces that are protected by time reversal symmetry. However, in common transport measurements residual bulk conductivity hinders the properties of the topologically protected surfaces. Alternatively, terahertz spectroscopy has recently been shown to be capable of discerning the bulk and surface carrier conductivity. Here we use time-resolved optical pump-THz probe spectroscopy at low temperatures to study the hot carrier response of thin films of Bi2Se3 of several thicknesses and separate the bulk from the surface response. We find that for thinner films the photo excitation changes the transport scattering rate and reduces the surface conductivity. For thicker films, this process competes with the photoinduced increase in bulk conductivity, which occurs on shorter timescales and scales with the increase in both the film thickness and optical excitation fluence. These different dynamics of the surface and bulk electrons indicate a decoupling of surface and bulk carriers, and present the possibility of accessing long-lived surface photo-carriers for optoelectronic applications.

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U2 - 10.1109/IRMMW-THz.2014.6956063

DO - 10.1109/IRMMW-THz.2014.6956063

M3 - Conference contribution

AN - SCOPUS:84911950536

T3 - International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

BT - 2014 39th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz 2014

PB - IEEE Computer Society

T2 - 39th International Conference on Infrared, Millimeter and Terahertz Waves, IRMMW-THz 2014

Y2 - 14 September 2014 through 19 September 2014

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