Breakthrough Computational Research Identifies Room Temperature Quantum Tunneling as a Primary Driver for Hydrogen Transport in Lanthanum Trihydride

New study reveals hydrogen ions tunnel through energy barriers in lanthanum trihydride at 308 K, providing a new quantum model for solid-state conductivity.

By: AXL Media

Published: Apr 29, 2026, 7:27 AM EDT

Source: Information for this report was sourced from EurekAlert!

Challenging the Classical Framework of Ionic Migration

For nearly a century, the movement of ions through solid materials has been understood as a thermally activated process where particles must gain enough energy to climb over physical potential barriers. However, new research published in Science Bulletin indicates that for hydrogen, the lightest element, this classical view is fundamentally incomplete. Investigators from the Institute of Physics at the Chinese Academy of Sciences and Fudan University have demonstrated that hydrogen in lanthanum trihydride often takes a quantum shortcut, passing through barriers rather than over them. This revelation marks a shift in how physicists view the movement of light atoms within solid state systems.

Identifying Practical Temperature Thresholds for Quantum Effects

The study utilized advanced first-principles calculations based on ring-polymer instanton theory to pinpoint exactly when quantum mechanics takes over from classical physics. Researchers found that for concerted migration, where multiple ions move together, quantum tunneling becomes the dominant transport mechanism at 71 K, which is near the temperature of liquid nitrogen. More importantly, for single-ion migration, this crossover temperature rises to 308 K. This suggests that quantum tunneling is a major factor at room temperature, contradicting the long held assumption that such effects are only relevant in extreme cryogenic environments.

The Decisive Role of Barrier Geometry in Particle Transport

By moving beyond classical models, the research team clarified why previous calculations often failed to accurately predict hydrogen behavior. In a classical system, the height of a barrier is the only factor that dictates the rate of migration. However, when nuclear quantum effects are included, the width of the barrier becomes equally critical. A narrow barrier allows hydrogen to tunnel with far greater ease than a tall, wide one. This discovery explains why the difference in migration rates between different pathways was previously overestimated, as the tunneling-friendly nature of narrow barriers was completely overlooked by traditional descriptions.