Quantum oscillations and electronic features in V1-<bold>δ</bold>Sb2 single crystals

Nonsymmorphic compounds have attracted much interest owing to their potential nontrivial electronic states. Here, we grew V1-delta Sb2 single crystal with a nonsymmorphic space group I4/mcm and studied their de Haas-van Alphen oscillations. Orientation-dependent magnetization showed quantum oscillations, allowing determination of the three-dimensional Fermi surface and Berry phase. Our theoretical calculation implied that VSb2's band structures manifest flat bands along the Gamma-X path, Dirac band crossings near the P and N points, and in the Gamma-Z direction, and nontrivial surface states along the Gamma( - )- Z<overline> line. However, the inconsistencies in observed and calculated quantum oscillation frequencies suggest that VSb2's band structures cannot nicely account for these electronic properties of our samples. This study reveals the profound impact of V vacancies on VSb2's electronic states, implying the possible topological quantum phase transition via defect engineering.