Experimental Evidence of Electron-enhanced Interfacial Thermal Conductance Through Two-Dimensional Electron Gas

Abstract

It has been a persistent challenge to experimentally distinguish the contribution of electron-phonon coupling on interfacial thermal conductance from phonon-dominated pathways. The LaAlO₃/SrTiO₃ (LAO/STO) interface offers a unique platform to address this, at which two-dimensional electron gas (2DEG) can be formed or absent depending on whether the LAO is terminated by TiO₂ or SrO during the growth, and enables a direct comparison of thermal transport with and without interfacial free electrons. Using time-domain thermoreflectance measurements, it is demonstrated that the interfacial thermal conductance is enhanced by 35–40% in the 2DEG-active interface compared to its 2DEG-free counterpart. This enhancement provides direct experimental evidence of electron-phonon coupling as an additional thermal transport channel, distinct from phonon contributions. The extracted electron-phonon coupling coefficient (G≈10¹⁶ W m⁻³ K⁻¹) aligns with the first-principles predictions for oxide interfaces. Crucially, the results resolve the long-standing ambiguity in decoupling electronic and phononic thermal pathways, offering a generalizable framework to quantify electron-phonon interactions at metal-dielectric heterointerfaces.