Band structure and polarization effects in photothermoelectric spectroscopy of a Bi2Se3 device

Bi2Se3 is a prototypical topological insulator, which has a small bandgap (∼0.3 eV) and topologically protected conducting surface states. This material exhibits quite strong thermoelectric effects. Here, we show in a mechanically exfoliated thick (∼100 nm) nanoflake device that we can measure the e...

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Bibliographic Details
Published in:Applied physics letters 2022-03, Vol.120 (12)
Main Authors: Pournia, Seyyedesadaf, Jnawali, Giriraj, Need, Ryan F., Jackson, Howard E., Wilson, Stephen D., Smith, Leigh M.
Format: Article
Language:English
Subjects:
Applied physics
Conduction bands
Linear polarization
Optical transition
Spectral signatures
Thermoelectric materials
Topological insulators
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Summary:Bi2Se3 is a prototypical topological insulator, which has a small bandgap (∼0.3 eV) and topologically protected conducting surface states. This material exhibits quite strong thermoelectric effects. Here, we show in a mechanically exfoliated thick (∼100 nm) nanoflake device that we can measure the energy dependent optical absorption through the photothermoelectric effect. Spectral signatures are seen for a number of optical transitions between the valence and conduction bands, including a broad peak at 1.5 eV, which is likely dominated by bulk band-to-band optical transitions but is at the same energy as the well-known optical transition between the two topologically protected conducting surface states. We also observe a surprising linear polarization dependence in the response of the device that reflects the influence of the metal contacts.
ISSN:0003-6951
1077-3118
DOI:10.1063/5.0075924