Lattice Dynamics of Bi2Те3 and Vibrational Modes in Raman Scattering of Topological Insulators MnBi2Te4·n(Bi2Te3)

Abstract

This work is devoted to the experimental study and symmetry analysis of the Raman-active vibration modes in MnBi2Te4·n(Bi2Te3) van der Waals topological insulators, where n is the number of Te–Bi–Te–Bi–Te quintuple layers between two neighboring Te–Bi–Te–Mn–Te–Bi–Te septuple layers. Confocal Raman spectroscopy is applied to study Raman spectra of crystal structures with $$n = 0,1,2,3,4,5,6$$, and ∞. The experimental frequencies of vibration modes of the same symmetry in the structures with different n are compared. The lattice dynamics of free-standing one, three, and four quintuple layers, as well as of bulk Bi2Те3$$(n = \infty )$$ and MnBi2Te4$$(n = 0)$$, is considered theoretically. Vibrational modes of the last two systems have the same symmetry, but different displacement fields. These fields in the case of a Raman-active mode do not contain displacements of manganese atoms for any finite $$n$$. It is shown that two vibrational modes in the low-frequency region of the spectrum (35–70 cm–1) of structures with $$n = 1,\;2,\;3,\;4,\;5$$, and 6 practically correspond to the lattice dynamics of n free quintuple Bi2Те3 layers. For this reason, the remaining two vibration modes, which are observed in the high-frequency region of the spectrum (100–140 cm–1) and are experimentally indistinguishable in the sense of belonging to quintuple or septuple layer or to both layers simultaneously, should also be assigned to vibrations in quintuple layers under immobile atoms of septuple layers.

Growth and characterization of the magnetic topological insulator candidate Mn2Sb2Te5

“…The strongest peaks of Mn-2p 3/2 and Mn-2p 1/2 peaks at 641.0 eV and 653.1 eV are due to the contribution of Mn 2+ in Mn-Te broken bonds which elucidates the major oxidation state of Mn is 2 + . A small separation between both 2p is found to be 12 eV although it is just close to the reported by other [26]. The other peaks of Mn 3+ associated with Mn-2p 3/2 and Mn-2p 1/2 identified at 642.5 eV and 654.8 eV, and Mn 4+ associated with Mn-2p 3/2 and Mn-2p 1/2 peaks identified at 645.0 eV and 657.9 eV are known as satellite peaks of Mn valence states.…”

“…Five Raman modes are observed at 61 ± 1 cm −1 , 86 ± 1 cm −1 , 116 ± 1 cm −1 , 117 ± 6 cm −1 , and 137 ± 1 cm −1 respectively through Lorentz deconvolution. All the observed peaks are different from as reported in mother compound Mn(Bi/Sb) 2 Te 4 [25,26]. Generally, in case of Mn(Bi/Sb) 2 Te 4 , five peaks are observed in which high frequency vibrational modes is observed between 50 and 120 cm −1 .…”

Transport Properties of the Magnetic Topological Insulators Family (MnBi2Te4)(Bi2Te3)m (m = 0, 1, …, 6)

“…After discovery [1][2][3][4][5] of the first antiferromagnetic (AFM) topological insulator (TI) MnBi 2 Te 4 , a large family of intrinsic magnetic TIs in the homologous series of compounds (MnBi 2 Te 4 )(Bi 2 Te 3 ) m were intensively studied [6][7][8][9][10][11]. These are layered crystals which consist of the 2D ferromagnetic (FM) septuple layer blocks of MnBi 2 Te 4 for , and the periodic set of septuple and m non-magnetic quintuple layer blocks of Bi 2 Te 3 for .…”

“…Magnetic and electronic transport properties of these materials depend strongly on the m value and are thus highly tunable. While [1,2,6] apart from the theoretical calculations, were mainly focused on the experimental studies of the surface electronic structure (using ARPES,) and bulk magnetism (using magnetometry) for , other studies considered magneto-transport properties of compounds: MnBi 2 Te 4 [11,14], MnBi 4 Te 7 [14,15], MnBi 6 Te 10 [14,15], MnBi 8 Te 13 [16]. However, to the best of our knowledge, the magneto-transport studies of the whole (MnBi 2 Te 4 )(Bi 2 Te 3 ) m family, i.e., for , [7,11,17] till now are absent.…”

“…While [1,2,6] apart from the theoretical calculations, were mainly focused on the experimental studies of the surface electronic structure (using ARPES,) and bulk magnetism (using magnetometry) for , other studies considered magneto-transport properties of compounds: MnBi 2 Te 4 [11,14], MnBi 4 Te 7 [14,15], MnBi 6 Te 10 [14,15], MnBi 8 Te 13 [16]. However, to the best of our knowledge, the magneto-transport studies of the whole (MnBi 2 Te 4 )(Bi 2 Te 3 ) m family, i.e., for , [7,11,17] till now are absent. Here we present for the first time the systematic studies of magneto-transport properties of this family with , namely, the temperature dependences of the resistivity , magnetoresistance and the Hall effect at low temperatures.…”