Infrared study of the multiband low-energy excitations of the topological antiferromagnet MnBi${}_2$Te${}_4$

Abstract

With infrared spectroscopy we studied the bulk electronic properties of the topological antiferromagnet MnBi${}_2$Te${}_4$ with $T_N\simeq 25\mathrm{K}$. With the support of band structure calculations, we assign the intra- and interband excitations and determine the band gap of $E_g\approx$ 0.17 eV. We also obtain evidence for two types of conduction bands with light and very heavy carriers. The multiband free carrier response gives rise to an unusually strong increase of the combined plasma frequency, ${\omega }_{\mathrm{pl}}$, below 300 K. The band reconstruction below $T_N$, yields an additional increase of ${\omega }_{\mathrm{pl}}$ and a splitting of the transition between the two conduction bands by about 54 meV. Our study thus reveals a complex and strongly temperature dependent multi-band low-energy response that has important implications for the study of the surface states and device applications.

16 pages, 15 figures

References in corpus (6)

• Topological Field Theory of Time-Reversal Invariant Insulators
• Quantized Anomalous Hall Effect in Magnetic Topological Insulators
• High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator
• Antiferromagnetic topological insulators
• Crystal growth and magnetic structure of MnBi2Te4
• Coexistence of Surface Ferromagnetism and Gapless Topological State in MnBi${}_2$Te${}_4$

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• Intrinsic magnetic topological insulators of the MnBi${}_2$Te${}_4$ family
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• Infrared study of the layered, magnetic insulator Mn(Bi${}_{0.07}$Sb${}_{0.93}$)${}_2$Te${}_4$ at low temperatures
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• Evolution of the optical response of the magnetic topological insulators Mn(Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_4$ with Sb content
• Giant and Broadband Circular Dichroism from Particle-Hole Symmetry Breaking in Weyl Semimetals