Electron–phonon coupling (EPC) and anisotropic thermal transport properties in a series of layered quaternary hydrides XYZH (X = Ba, Sr; Y = Al, Ga; Z = Si, Ge) are systematically investigated via first-principles calculations. These compounds form covalent H–Y–Z layers separated by weakly bonded X atoms. Despite pronounced structural anisotropy, charge transport exhibits unexpectedly weak directional dependence. In contrast, the lattice thermal conductivity exhibits relatively weak anisotropy, with high-frequency hydrogen-dominated optical phonons making unexpectedly substantial contributions to cross-plane heat conduction. EPC strength is found to be highly sensitive to carrier type and composition, being strongest for p-type carriers in AlSi-based systems due to the high electronic density of states near the valence band maximum. Notably, p-type doping induces markedly stronger EPC than n-type doping, leading to a greater reduction in lattice thermal conductivity. This study unveils the unique vibrational and electron–phonon coupling mechanisms in these layered hydrides, providing critical insights for their potential applications in thermal management.
Yan et al. (Mon,) studied this question.