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We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-x with angle-resolved photoemission spectroscopy. Furthermore, we found that excess Fe (y>0) inhibits the topological band inversion in Fe1+yTexSe1-x, which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-x with excess Fe. Basing on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may able to tune the topological transition via applying lattice strain or carrier doping.

The A15 structure of superconductors is a prototypical type-II superconductor that has generated considerable interest since the early history of superconducting materials. This paper discusses the superconducting properties of previously unreported V3−x Co x Si (0 ⩽ x ⩽ 0.30) alloys. It is found that the lattice parameter decreases with increasing cobalt-doped content and leads to an decreased residual resistivity ratio value of the V3−x Co x Si system. Meanwhile, the superconducting transition temperature (Tc ) also decreases with increasing cobalt-doped content. Furthermore, the fitted data show that the increase of cobalt-doped content also reduces the lower/upper critical fields of the V3−x Co x Si system. Type-II superconductivity is demonstrated in all V3−x Co x Si samples. With higher Co-doped content, V3−x Co x Si (0.15 ⩽ x ⩽ 0.30) alloys may have superconducting and structural phase transitions in low-temperature regions. As the electron/atom ratio increases, the Tc variation trend of V3Si is as pronounced as in crystalline alloys and monotonically follows the trend observed for amorphous superconductors.

The Kitaev model for magnetic interactions on a honeycomb lattice, which underlies the exotic quantum spin liquid (QSL) state in such systems, has long been established and experimentally confirmed. Current studies on Kitaev QSLs have focused on heavy-metal-based Mott insulators where strong spin-orbit coupling (SOC) leads to bond-dependent spin anisotropy. Here we examine a 3d transition-metal-based honeycomb lattice material BaNi2(As1-x V x )2O8, where the SOC is weak but spin exchange coupling is strongly frustrated due to the crystal field. We present an investigation of the crystal structure and magnetization of this series of Ni-based honeycomb materials, providing an alternative perspective in the search for the QSL in 3d-element-based honeycomb systems.