Extremely large magnetoresistance with coexistence of a nontrivial Berry phase in Nb0.5Ta0.5P: an experimental and theoretical study

In our study, we focused on Weyl semimetals NbP and TaP, known for their remarkable magnetoresistance (MR) at low temperatures due to charge carrier compensation. We synthesized an intermediate compound, Nb0.5Ta0.5P, which also exhibits extremely large magnetoresistance (XMR) at low temperatures. Although its MR% is one order of magnitude lower than that of the parent systems, Nb0.5Ta0.5P demonstrates perfect charge carrier compensation up to 50 K. The magnetoresistance in this compound follows an B-2 dependence and mirrors the classical carrier mobility's temperature dependence. We noticed a deviation from Kohler's rule in both instances, demonstrating the existence of multiple kinds of charge carriers. We conducted an analysis of Shubnikov-de Haas (SdH) oscillations to investigate the Fermi surface evolution and the presence of a nontrivial Berry phase in all three compounds. In Nb0.5Ta0.5P, quantum oscillations revealed multiple Fermi pockets. Additionally, density functional theory (DFT) calculations predicted bulk band structure features near the Fermi level, including band-crossing points. Changes in the density of states between the parent and doped systems were systematically observed, with the inclusion of spin-orbit coupling (SOC) revealing a band gap opening at Weyl node points. The significant enhancement in magnetoresistance observed in Nb0.5Ta0.5P at room temperature suggests promising avenues for exploring similar systems with suitable substitutions to develop new high-performance materials for industrial applications.