Single Crystal Growth and Transport Properties of van der Waals Materials ABTe4 (A/B = Ti, Zr, Hf)

Monolayers of ABTe₄ (A/B = Ti, Zr, Hf) were theoretically predicted to be two-dimensional topological insulators, but little has been known about the physical properties of these compounds. Here, we report on the single crystal growth, bulk transport properties, and band structure calculations of these compounds. The magnetotransport properties indicate that all three compounds are multi-carrier systems. The experimental results of ZrTiTe₄ and HfTiTe₄ can be well fitted by the multi-carrier formula assuming two types of carriers, while three carrier components were necessary for HfZrTe₄. Interestingly, one of the carrier mobilities of HfZrTe₄ exceeded 1000 cm² V⁻¹ s⁻¹, which was nearly one order in magnitude larger than the carrier mobilities of ZrTiTe₄ and HfTiTe₄. Our band structure calculations showed that all three compounds are semimetals consistent with the magnetotransport properties. The band structure around the Γ-point of HfZrTe₄ exhibits features that are distinct from the other two compounds, which is likely the reason of the different carrier properties.