Mobility-Controlled Extremely Large Magnetoresistance In Perfect Electron-Hole Compensated Alpha-Wp2 Crystals

Recent studies discovered that the binary transition-metal compounds A(x)B(y) demonstrate extremely large magnetoresistance (XMR) undermagnetic field B,for example, 10(6)% inPtBi(2) and 10(5)% in WTe2. The underlying physical origins, however, are quite diverse, such as electron-hole balance, backscattering forbidden of Dirac/Weyl fermions, and high mobility. Here we experimentally find an ideal compound (alpha-WP2) where the perfect electronhole compensation can be sustained within a large temperature range (from 2 to 100 K). The XMR of alpha-WP2 is measured as high as 8.74x10(5)% under 9 T B at 2 K, but it is remarkably decreased from 8.74x10(5)% to 18% when the temperature is raised from 2 to 100 K; simultaneously, the mobility is decreased by more than two orders of magnitude. Magnetotransport characterizations show that MR is proportional to B-2 and the pronounced dHvA quantum oscillations come from the conventional Schrodinger fermions in alpha-WP2, which rules out the possibility of Dirac fermions. These evidences strongly suggest that XMR observed in binary A(x)B(y) semimetals is mainly attributed to high mobility, rather than Dirac/Weyl fermions, or resonant electron-hole compensation. This work elucidates the underlying physical origin of XMR in these compounds.