Bonding and Electronic Nature of the Anionic Framework in LaPd₃S₄

Abstract

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 μ0 H = 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.

Bonding and Suppression of a Magnetic Phase Transition in EuMn2P2

“…The bonding in solids is often complex, driven by the ability of a multicomponent system to minimize interactions on different length scales through the formation of complex, emergent, states. This gives rise to a variety of exotic and useful electrical and magnetic properties, including charge and magnetic order, charge, and spin density waves, and superconductivity. − The precise ground-state configuration of electrons is determined by a subtle interplay between electron–nuclear and electron–electron interactions that is set by the local atomic bonding between atoms. When a material’s structure has two distinct magnetic subunits, then the separation of energy scales within and between subunits can give rise to distinct behaviors that would not arise with a single homogeneous magnetic lattice.…”