Magnetoinfrared spectroscopic study of thinBi2Te3single crystals

Abstract

Thin ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at $4\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and in a magnetic field up to $35\phantom{\rule{0.222222em}{0ex}}\mathrm{T}$. The magnetotransmittance spectra of the ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$/tape composite are analyzed as a stacked-slab system, and the average thickness of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ is estimated to be $6.4\ifmmode\pm\else\textpm\fi{}1.7\phantom{\rule{0.222222em}{0ex}}\ensuremath{\mu}\mathrm{m}$. The optical conductivity of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ at different magnetic fields is then extracted, and we find that the magnetic field modifies the optical conductivity in the following ways: (1) Field-induced transfer of the optical weight from the lower-frequency regime $(<250\phantom{\rule{0.222222em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1})$ to the higher-frequency regime $(>250\phantom{\rule{0.222222em}{0ex}}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1})$ due to the redistribution of charge carriers across the Fermi surface. (2) Evolving of a Fano-resonance-like spectral feature from an antiresonance to a resonance with increasing magnetic field. Such behavior can be attributed to the electron-phonon interactions between the ${E}_{u}^{1}$ optical phonon mode and the continuum of electronic transitions. (3) Cyclotron resonance resulting from the intervalence band Landau level transitions, which can be described by the electrodynamics of massive Dirac holes.