Infrared study of the multiband low-energy excitations of the topological antiferromagnet MnBi2Te4

With infrared spectroscopy, we studied the bulk electronic properties of the topological antiferromagnet MnBi2Te4 with TN≃25K. With the support of band-structure calculations, we assign the intra- and interband excitations and determine the band gap of Eg≈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, ωpl, below 300 K. The band reconstruction below TN yields an additional increase of ωpl 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 multiband low-energy response that has important implications for the study of the surface states and device applications.The work in Fribourg was supported by the Schweizerische Nationalfonds (SNF) through Grant No. 200020-172611. V.K. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG) through Grant No. KA1694/12-1. N.M. acknowledges the support of the Science Development Foundation under the President of the Republic of Azerbaijan (Grant No. E˙IF-BGM-4-RFTF1/2017-21/04/1-M-02). The work at Beijing was supported by the Natural Science Foundation of China (NSFC Grant No. 11734003), the National Key R&D Program of China (Grants No. 2016YFA0300600 and No. 2020YFA0308800), and the Beijing Natural Science Foundation (Grant No. Z190006). Z.W. acknowledges the support from Beijing Institute of Technology Research Fund Program for Young Scholars. B.S. acknowledges the support of the Fundamental Research Funds for the Central Universities, Grant No. 19lgpy260. E.V.C. acknowledges Saint Petersburg State University (Grant No. ID 73028629). Y.M.D. acknowledges the support of the Natural Science Foundation of China (Grant No. 11874206). M.M.O. acknowledges the support by Spanish Ministerio de Ciencia e Innovación (Grant No. PID2019-103910GB-I00).Peer reviewe

Infrared study of the multiband low-energy excitations of the topological antiferromagnet MnBi2Te4

With infrared spectroscopy, we studied the bulk electronic properties of the topological antiferromagnet MnBi2Te4 with TN ≃ 25 K. With the support of band-structure calculations, we assign the intra- and interband excitations and determine the band gap of Eg ≈ 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, ωpl, below 300 K. The band reconstruction below TN yields an additional increase of ωpl 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 multiband low-energy response that has important implications for the study of the surface states and device applications