Correlation of crystal quality and extreme magnetoresistance of WTe 2

High-quality single crystals of WTe2 were grown using a Te flux followed by a cleaning step involving self-vapor transport. The method is reproducible and yields consistently higher-quality single crystals than are typically obtained via halide-assisted vapor transport methods. Magnetoresistance (MR) values at 9 tesla and 2 kelvin as high as 1.75 million %, nearly an order of magnitude higher than previously reported for this material, were obtained on crystals with residual resistivity ratio (RRR) of approximately 1250. The MR follows a near B 2 law and, assuming a semiclassical model, the average carrier mobility for the highest-quality crystal was found to be at 2 K. A correlation of RRR, MR ratio and average carrier mobility is found with the cooling rate during the flux growth.