Magnetoresistance induced by rare strong scatterers in a high-mobility two-dimensional electron gas

We observe a strong negative magnetoresistance at nonquantizing magnetic fields in a high-mobility two-dimensional electron gas. This strong negative magnetoresistance consists of a narrow peak around zero magnetic field and a huge magnetoresistance at larger fields. The peak shows parabolic magnetic field dependence and is attributed to the interplay of smooth disorder and rare strong scatterers. We identify the rare strong scatterers as macroscopic defects in the material and determine their density from the peak curvature.