Double Dirac materials are a topological phase of matter in which a non-symmorphic symmetry enforces greater electronic degeneracy than normally expected up to eightfold. The cubic palladium bronzes NaPd3O4 and LaPd3S4 are built of Pd3X4 (X = O, S) anionic frameworks that are ionically bonded to A cations (A = Na, La). These materials were recently identified computationally as harboring eightfold fermions. Here we report the preparation of single crystals and electronic properties of LaPd3S4. Measurements down to T = 0.45 K and in magnetic fields up to μ0H = 65 T are consistent with normal Fermi liquid physics of a Dirac metal in the presence of dilute magnetic impurities. This interpretation is further confirmed by analysis of specific heat, magnetization measurements and comparison to density functional theory (DFT) calculations. Through a bonding analysis of the DFT electronic structure of NaPd3O4 and LaPd3S4, we identify the origin of the stability of the anionic Pd3X4 framework at higher electron counts for X = S than X = O, and propose chemical tuning strategies to enable shifting the 8-fold fermion points to the Fermi level.
@article{arxiv.2207.03387,
title = {Bonding and Electronic Nature of the Anionic Framework in LaPd$_3$S$_4$},
author = {Tanya Berry and Michael Nicklas and Qun Yang and Walter Schnelle and Rafał Wawrzyńczak and Tobias Förster and Johannes Gooth and Claudia Felser and Tyrel M. McQueen},
journal= {arXiv preprint arXiv:2207.03387},
year = {2022}
}