Kondo Insulator to Semimetal Transformation Tuned by Spin-Orbit Coupling

• Main Authors: Dzsaber, S, Prochaska, L, Sidorenko, A, Eguchi, G, Svagera, R, Waas, M, Prokofiev, A, Si, Q, Paschen, S
• Format: Journal Article
• Language: English
• Published: 16-06-2017
• Subjects: Physics - Strongly Correlated Electrons
• DOI: 10.48550/arxiv.1612.03972

Phys. Rev. Lett. 118, 246601 (2017) Recent theoretical studies of topologically nontrivial electronic states in
Kondo insulators have pointed to the importance of spin-orbit coupling (SOC)
for stabilizing these states. However, systematic experimental studies that
tune the SOC parameter $\lambda_{\rm{SOC}}$ in Kondo insulators remain elusive.
The main reason is that variations of (chemical) pressure or doping strongly
influence the Kondo coupling $J_{\text{K}}$ and the chemical potential $\mu$ --
both essential parameters determining the ground state of the material -- and
thus possible $\lambda_{\rm{SOC}}$ tuning effects have remained unnoticed. Here
we present the successful growth of the substitution series
Ce$_3$Bi$_4$(Pt$_{1-x}$Pd$_x$)$_3$ ($0 \le x \le 1$) of the archetypal
(noncentrosymmetric) Kondo insulator Ce$_3$Bi$_4$Pt$_3$. The Pt-Pd substitution
is isostructural, isoelectronic, and isosize, and therefore likely to leave
$J_{\text{K}}$ and $\mu$ essentially unchanged. By contrast, the large mass
difference between the $5d$ element Pt and the $4d$ element Pd leads to a large
difference in $\lambda_{\rm{SOC}}$, which thus is the dominating tuning
parameter in the series. Surprisingly, with increasing $x$ (decreasing
$\lambda_{\rm{SOC}}$), we observe a Kondo insulator to semimetal transition,
demonstrating an unprecedented drastic influence of the SOC. The fully
substituted end compound Ce$_3$Bi$_4$Pd$_3$ shows thermodynamic signatures of a
recently predicted Weyl-Kondo semimetal.