Electron Doping of $\mathrm{La_3Ni_2O_7}$ Thin Films: Candidate Metal Dopants and Their Potential Impact on Superconductivity

Abstract

The bilayer Ruddlesden-Popper nickelate $\mathrm{La_3Ni_2O_7}$ has emerged as a promising platform for exploring and understanding high-temperature superconductivities. While most prior doping studies have focused on hole doping via strontium (Sr) substitution or by tuning oxygen content, electron doping remains largely unexplored. In this work,we systematically investigate electron doping in $\mathrm{La_3Ni_2O_7}$ thin films through tetravalent element substitution, employing first-principles density functional theory calculations. Our results reveal that, unlike in cuprates, $\mathrm{cerium}$ (Ce) doping is difficult to effectively introduce electron carriers into the low-energy bands. In contrast, zirconium (Zr), hafnium (Hf), and thorium (Th) can act as efficient electron dopants. These element substitutions can significantly increase the interlayer hopping $t_{\perp}$ between $d_{z^2}$ orbitals, which may lead to enhanced superexchange coupling $J_{\perp}$ , and thereby potentially elevated superconducting $T_c$. We evaluate the interaction parameters using constrained random phase approximation. Our results identify candidate dopants for achieving electron-doped $\mathrm{La_3Ni_2O_7}$, offering a route to clarify the ongoing debate on pairing mechanisms in this system.