Transport in the Magnetic Weyl Semimetal Y₂Ir₂O₇

Despite their name, the behavior of undoped Weyl Semimetals (WSMs) should be semiconducting-like, with resistivity exhibiting a negative temperature coefficient, dρ/dT < 0. Unlike semiconductors (either intrinsic or those exhibiting variable range hopping) however, the density of states in WSMs will exhibit power law behavior at points or lines in the Brillouin zone, which leads to inverse power law behavior in ρ(T). We show that an inverse quartic law, as predicted for charged impurity scattering, is consistent with existing data on the rare-earth iridate pyrochlores, R₂Ir₂O₇ as a limiting form. We also show that for R = Y, ρ ∝ T^-4 over four orders of magnitude in ρ, extending into a temperature range where k_Fl << 1, suggesting behavior of a “bad” WSM. A picture of localization into deep potential wells with strong electron correlations is supported by thermopower data on the same samples. Transport and thermodynamic data will also be presented for different pyrochlore lattice systems of the general form Li₂M₂O₇, where M = Ir, Os, Ru, and Rh, for which power law behavior is also observed.

P. G. LaBarre, L. Dong, J. Trinh, T. Siegrist, A. P. Ramirez, J. Phys. Cond Mat., 32, 02LT01 (2020)