Investigation of magnetotransport properties of topological surface states in SnBi₄Te₇ single crystal

The magnetotransport properties of SnBi₄Te₇ single crystal are presented here. The magnetoresistance measurements uncover the presence of a weak antilocalization (WAL) effect. A modified Hikami–Larkin–Nagaoka equation is used to fit the behavior of the low field magnetotransport, and two important parameters are extracted: the pre-factor (α) and the phase coherence lengths (l_ϕ). The estimated α value, particularly at lower temperatures, is closed to one, signifying the two surface states are separated by insulating bulk. However, this dominance diminishes as the temperature increases from the lowest measured temperature (T = 2 K). Phase coherence length’s temperature dependence is explained by two-dimensional (2D) electron–electron (e–e) and 2D electron–phonon (e–p) interactions. The three-dimensional (3D) WAL and the 2D WAL/electron–electron interactions model agree with the temperature-dependent resistivity data. The measured Hall resistivity of the single crystal indicates that the holes are the majority carriers. The existence of non-trivial topological surface states is also confirmed through electronic structure calculations, which reveal the presence of (0;001) Z₂ topological invariants.