Effects of Se-doping in topological hourglass semimetal Nb₃SiTe₆

Abstract In low-dimensional superconducting systems, novel properties emerge due to quantum confinement effects, enhanced electron correlations and spin-orbit interactions. Nb₃SiTe₆ is a topological hourglass semimetal with both one-dimensional (1D) and two-dimensional (2D) electronic states, as well as flat bands. Such rich band characteristics make it an ideal platform for modulating and studying the effects of band structure and dimensionality. With Se substitution, the Fermi level and carrier concentration of Nb₃Si(Te 1− x Se x )₆ are modulated, causing the emergence of superconductivity, which may be attributed to the contributions of flat bands or the formation of 1D NbSe 2 chains. Consequently, the upper critical field ( H c2 ) presents an unconventional temperature dependence, deviating from the 2D Ginzburg–Landau model. Angular-dependent magneto-resistance results demonstrate the 2D electronic and superconducting state and the more robust out-of-plane upper critical field induced by the enhanced superconducting vortex pinning effect. Our results suggest that Se doped Nb₃SiTe₆ is a suitable system to study low-dimensional superconductivity, physics of flat bands, and the superconducting vortex.