Discovery of Superconductivity in the Quasi-One-Dimensional SrBi₂Se₄ Single Crystals

We report the discovery of superconductivity in the quasi-one-dimensional (Q-1D) SrBi₂Se₄ single crystals grown by the self-flux method. It is found that the resistivity displays a metallic behavior in the normal state, followed by a superconducting transition at low temperatures, distinctly different from the semiconducting behavior of the previously reported polycrystalline samples. Both magnetization and specific heat measurements reveal the bulk nature of superconductivity. The extrapolated value of upper critical field μ₀H_c2(0) for H||c is ∼2.4 times larger than the Pauli limit. More intriguingly, the field dependence of resistivity at certain temperatures exhibits an anomalously hump-like feature for H⊥c; that is, the finite resistivity due to vortex motion in the dissipative state first increases with magnetic fields and then unexpectedly drops back to zero at higher fields, indicating the reentrant vortex pinning induced by increasing magnetic fields. The discovery of superconductivity in SrBi₂Se₄ single crystals thus provides a novel material platform to study the exotic superconductivity in the Q-1D electron systems.