Ground state of Ce3Bi4Pd3 unraveled by hydrostatic pressure

Recent theoretical predictions of non-trivial topological states in Kondo insulators have boosted investigations on candidate materials. For instance, Ce$_3$Bi$_4$Pd$_3$, a noncentrosymmetric compound crystallizing in the same structure of the prototypical Kondo insulator Ce$_3$Bi$_4$Pt$_3$, has been predicted to be a Weyl Kondo semimetal driven by spin-orbit coupling [1]. Conflicting experimental results, however, argue for either a Weyl Kondo semimetallic or a narrow-gap Kondo insulating ground state [2-4]. Here we use electrical transport measurements under hydrostatic pressure to provide insights in to the ground-state properties of Ce$_3$Bi$_4$Pd$_3$. Our results reveal that Ce$_3$Bi$_4$Pd$_3$ becomes more insulating with increasing pressure, a behavior typical of Kondo insulators such as Ce$_3$Bi$_4$Pt$_3$. Moreover, the hybridization gap shows a quadratic increase with pressure akin to the effect of Pt substitution observed in Ce$_3$Bi$_4$(Pt$_{1-x}$Pd$_x$)$_3$ series [2]. These results suggest that the Kondo coupling prevails as the primary tuning parameter in these materials and Ce$_3$Bi$_4$Pd$_3$ is indeed a narrow-gap version of the Ce$_3$Bi$_4$Pt$_3$ Kondo insulator.
[1] H.-H. Lai, S. E. Grefe, S. Paschen, and Q. Si, Proc. Natl. Acad. Sci. U.S.A. 115, 93 (2018).
[2] S. Dzsaber, L. Prochaska, A. Sidorenko, G. Eguchi, R. Svagera, M. Waas, A. Prokofiev, Q. Si, and S. Paschen, Phys. Rev. Lett. 118, 246601(2018).
[3] S. Dzsaber, X. Yan, M. Taupin, G. Eguchi, A. Prokofiev, T. Shiroka, P. Blaha, O. Rubel, S. E. Grefe, H.-H. Lai, Q. Si, and S. Paschen, Proc. Natl. Acad. Sci. U.S.A. 118, e2013386118 (2021).
[4] S. K. Kushwaha, M. K. Chan, J. Park, S. M. Thomas, E. D. Bauer, J. D. Thompson, F. Ronning, P. F. S. Rosa, and N. Harrison, Nat. Comm. 10, 5487 (2019).