Magneto-Infrared Spectroscopic Study of Ultrathin Bi$_{2}$Te$_{3}$ Single Crystals

TL;DR

This study uses magneto-infrared spectroscopy to explore how magnetic fields affect the optical properties of ultrathin Bi$_{2}$Te$_{3}$ crystals, revealing charge redistribution, electron-phonon interactions, and Landau level transitions.

Contribution

It provides new insights into the magneto-optical behavior of ultrathin Bi$_{2}$Te$_{3}$, including the analysis of optical conductivity changes and electron-phonon coupling under high magnetic fields.

Findings

Magnetic field causes transfer of optical weight from low to high frequencies.

Fano-resonance evolves from anti-resonance to resonance with increasing field.

Cyclotron resonance observed from inter-valence band Landau level transitions.

Abstract

Ultrathin Bi$_{2}$Te$_{3}$ single crystals laid on Scotch tape are investigated by Fourier transform infrared spectroscopy at $4$K and in a magnetic field up to $35$T. The magneto-transmittance spectra of the Bi$_{2}$% Te$_{3}$/tape composite are analyzed as a two-layer system and the optical conductivity of Bi$_{2}$Te$_{3}$ at different magnetic fields are extracted. We find that magnetic field modifies the optical conductivity in the following ways: (1) Field-induced transfer of the optical weight from the lower frequency regime ($<250$cm$^{-1}$) to the higher frequency regime ($% >250$cm$^{-1}$) due to the redistribution of charge carriers across the Fermi surface. (2) Evolving of a Fano-resonance-like spectral feature from an anti-resonance 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 inter-valence band Landau level transitions, which can be described by the electrodynamics of massive Dirac holes.