Giant Negative Magnetoresistance beyond Chiral Anomaly in Topological Material YCuAs₂

The large negative magnetoresistance (MR) effect, which usually emerges in various magnetic systems, is a technologically important property for spintronics. Recently, the so-called "chiral anomaly" in topological semimetals offers an alternative to generate a considerable negative MR effect without utilizing magnetism. However, it requires that the applied magnetic field must be strictly along the electric current direction, which sets a strong limit for practical applications. Here, a giant negative MR effect is discovered with a value of up to -40% in 9 T at 2 K in the nonmagnetic Dirac material YCuAs₂ , which is not restricted to the specific configuration for applied magnetic fields. Based on magnetic susceptibility and NMR measurements, the giant negative MR effect is tightly connected with the unexpected spin-dependent scattering from vacancy-induced local moments, which is also beyond the classical Kondo effect. The present work not only offers an alternative route for spintronics based on nonmagnetic topological materials, but also helps to further understand the negative MR effect in topological materials.