Strongly tunable Ising superconductivity in van der Waals NbSe_2–xTe_x nanosheets

Ising superconductivity, induced by the strong spin–orbit coupling (SOC) and inversion symmetry breaking, can lead to the in-plane upper critical field exceeding the Pauli limit and hold significant potential for advancing the study of topological superconductivity. However, the enhancement of Ising superconductivity is still a challenging problem, important for engineering Majorana fermions and exploring topological quantum computing. In this study, we investigated the superconducting properties of a series of van der Waals NbSe_2−xTe_x nanosheets. The Ising superconductivity in NbSe_2−xTe_x nanosheets can be significantly enhanced by the substitution of Te, an element with strong SOC. The fitted in-plane upper critical field of NbSe_1.5Te_0.5 nanosheets at absolute zero temperature reaches up to 3.2 times the Pauli limit. Angular dependence of magnetoresistance measurements reveals a distinct two-fold rotational symmetry in the superconducting transition region, highlighting the role of strong SOC. In addition, the fitting results of the Berezinskii–Kosterlitz–Thouless (BKT) transition and the two-dimensional (2D) Tinkham formula provide strong evidence for 2D superconductivity. These findings offer new perspectives for the design and modulation of the Ising superconducting state and pave the way for their potential applications in topological superconductivity and quantum technologies.