Tuning the ground state of a candidate Weyl semimetal Eu₂Ir₂O₇ by Bi doping

The interplay of spin-orbit coupling (λ) and onsite coulomb interactions (U) in the pyrochlore iridates A₂Ir₂O₇ has been predicted to give rise to a plethora of non-trivial topological phases. Here we investigate the pyrochlore series (Eu_1-xBi_x)₂Ir₂O₇ whose end members are located in two different regions of the λ-U phase space. Eu₂Ir₂O₇ (EIO) shows a metal to insulator (MI) transition at 120 K concomitant with an antiferromagnetic ordering where the Ir moments order in an all-in/all-out(AIAO) structure. EIO is predicted to be a Weyl semimetal; whereas Bi₂Ir₂O₇ (BIO) is a non-Fermi liquid metal with at least two magnetic transitions below 2 K. In this presentation, we show that Bi substitution as high as 3.5% dopes electrons in the system without altering the electronic structure and tunes the Fermi energy with little change in MI/AIAO transitions. However at higher doping levels both these transitions are very strongly suppressed. The sample prepared with 10% Bi doping showed an highly unconventional metallic behaviour and no signs of MI/AIAO ordering down to at least 2 K. For higher doping, the behaviour gradually evolved to that of BIO. Our study exemplifies the appearance of unusual behaviours at the boundary between Weyl semimetal and non-Fermi liquid of the λ-U phase space.