We have discovered a new mechanism for the extreme magnetoresistance (XMR) of order 105 % recently reported in rocksalt-structure, nonmagnetic semimetals. Under this mechanism, rather than deriving from topological protection or perfect carrier compensation, XMR can also result from the cooperative action of a substantial difference in hole and electron mobility under moderate carrier compensation.
This work challenges prevailing views that topologically nontrivial electronic states or perfect carrier compensation are the exclusive mechanisms for XMR.
High quality single crystals of YbSb were prepared in the Emerging Materials Group via flux method. Crystals were well-suited to ARPES measurements (Figure) that showed no prima facie evidence for topological protection, one of the mechanisms suggested for XMR in related systems. The ARPES bandstructure could be analyzed to estimate the electron and hole pocket volumes, and hence an e/h ratio of ~0.8, far from the perfectly compensated semimetal mechanism suggested as an alternative to topological protection. Using the measured e/h ratio as an input to a standard two-band model for conduction led to successful modeling of the measured magnetotransport data up to 9 T subject to a significant imbalance in electron and hole mobility, mh/me ~250. Subsequent measurement of the Hall conductivities yielded mh/me ~15, indicating that the two band-model may be inadequate for describing the transport in this uncompensated semimetal.
This work was carried out in collaboration with the ALS, Stanford University, SLAC, and SiMES. Work at Argonne was supported by DOE-BES Materials Science and Engineering Division.
“Distinct Electronic Structure for the Extreme Magnetoresistance in YSb” J. He, C. Zhang, N.J. Ghimire, T. Liang, C. Jia, J. Jiang, S.Tang, S. Chen,Y. He, S.-K. Mo, C.C. Hwang,M. Hansmoto, D.H. Lu, B. Moritz,T.P. Devereau, Y.L. Chen, J.F. Mitchell and Z.-X. Shen Phys Rev. Lett. 117m 267201 (2016). http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.267201