Structural and Spectroscopic Properties of Doped and Undoped Substoichiometric Lanthanum Trihydrides

Hydride materials are gaining attention for their potential to achieve room-temperature superconductivity, a major scientific goal. In this study, we investigate the effects of both doping and pressure on sub-stoichiometric lanthanum hydrides (LaH_3-x). These materials exhibit an intriguing insulator-to-metal transition around 250 K, which may signal hidden superconducting properties. To probe this, we synthesized both undoped LaH_3-x and nitrogen-doped LaH_3-xN_y at Sandia National Lab and performed temperature-dependent X-ray diffraction, neutron diffraction at the SNAP beamline at ORNL, and high-pressure Raman spectroscopy. Neutron diffraction enabled us to study the hydrogen sublattice and reveal how nitrogen occupies vacancies in the structure—details that X-ray methods alone couldn’t capture.



Our initial results show that nitrogen doping has a strong impact on electronic properties, potentially stabilizing new phases that could lead to unique transport properties. By using nitrogen to introduce low Z element doping, we aim to explore the structural changes and potential for achieving superconductivity at near-ambient conditions. Alongside this, we are also studying band gap closure in LaH_3-x under high pressures. These findings open exciting possibilities for both undoped and nitrogen-doped hydrides as promising candidates for superconductivity close to ambient conditions.