Tomczak, J. M. (2020). Isoelectronic tuning of heavy fermion systems: Proposal to synthesize Ce₃Sb₄Pd₃. Physical Review B, 101(3), Article 035116. https://doi.org/10.1103/physrevb.101.035116
The study of (quantum) phase transitions in heavy fermion compounds relies on a detailed understanding
of the microscopic control parameters that induce them. While the influence of external pressure is rather
straightforward, atomic substitutions are more involved. Nonetheless, replacing an elemental constituent of a
compound with an isovalent atom is, effects of disorder aside, often viewed as merely affecting the lattice
constant. Based on this picture of chemical pressure, the unit-cell volume is identified as an empirical proxy
for the Kondo coupling. Here, instead, we propose an “orbital scenario” in which the coupling in complex
systems can be tuned by isoelectronic substitutions with little or no effect onto cohesive properties. Starting with
the Kondo insulator Ce3Bi4Pt3, we consider, within band theory, isoelectronic substitutions of the pnictogen
(Bi → Sb) and/or the precious metal (Pt → Pd). We show for the isovolume series Ce3Bi4(Pt1−xPdx )3 that
the Kondo coupling is in fact substantially modified by the different radial extent of the 5d (Pt) and 4d (Pd)
orbitals, while spin-orbit coupling mediated changes are minute. Combining experimental Kondo temperatures
with simulated hybridization functions, we also predict effective masses m∗, finding excellent agreement
with many-body results for Ce3Bi4Pt3. Our analysis motivates studying the so-far unknown Kondo insulator
Ce3Sb4Pd3, for which we predict m∗/mband = O(10).
