Predicting new heavy fermion materials within carbon-boron clathrate structures

Heavy fermion materials have been a rich playground for strongly correlated physics for decades. However, engineering tunable and synthesizable heavy fermion materials remains a challenge. We strive to integrate heavy fermion properties into carbon-boron clathrates as a universal structure which can host a diverse array of interesting physical phenomena. Using a combination of density functional theory and dynamical mean-field theory, we study two rare-earth carbon-boron clathrates, ${\mathrm{SmB}}₃{\mathrm{C}}₃$ and ${\mathrm{CeB}}₃{\mathrm{C}}₃$, and explore properties arising from the strong electronic correlations. We find a significant increase in the density of states at the Fermi level in ${\mathrm{CeB}}₃{\mathrm{C}}₃$ as the temperature is lowered, indicating the development of a heavy electron state. In ${\mathrm{SmB}}₃{\mathrm{C}}₃$, a potential Kondo insulating state is identified. Both findings point to rare-earth carbon-boron clathrates as novel strongly correlated materials within a universally tunable structure, offering a fresh platform to innovate upon conventional heavy fermion materials design.