Phonon modes and Raman signatures of MnBi2nTe3n+1(n=1,2,3,4) magnetic topological heterostructures

Abstract

An intrinsic antiferromagnetic topological insulator MnBi2Te4 arises when intercalating a Mn-Te bilayer chain in a topological insulator, Bi2Te3. We present observations on the inter- and intralayer phonon modes of the generalized MnBi2nTe3n+1(n=1,2,3,4) family using cryogenic low-frequency Raman spectroscopy with various polarization configurations. Two peaks at 66 and 112cm-1 show abnormal perturbation in Raman linewidths below magnetic transition temperature due to spin-phonon coupling. In MnBi4Te7, Bi2Te3 layers induce Davydov splitting of the A1g mode around 137cm-1 at 5 K. The out-of-plane interlayer force constant estimated using the linear chain model was (3.98±0.14)×1019N/m3, three times weaker than that of Bi2Te3. Adding more Bi2Te3 layers, such as MnBi6Te10 and MnBi8Te13, makes Bi2Te3 properties more dominant than magnetic properties. Our work experimentally and theoretically discovers the dynamics of phonon modes of MnBi2nTe3n+1 family, facilitating utilization of magnetic topological heterostructures.