Ultrafast light-matter interactions inspire potential functionalities in picosecond optoelectronic applications. However, achieving directional carrier dynamics in metals remains challenging due to strong carrier scattering within a multiband environment, typically expected to isotropic carrier relaxation. In this study, we demonstrate epitaxial RuO2/TiO2 (110) heterostructures grown by hybrid molecular beam epitaxy to engineer polarization-selectivity of ultrafast light-matter interactions via anisotropic strain engineering. Combining spectroscopic ellipsometry, X-ray absorption spectroscopy, and optical pump-probe spectroscopy, we revealed the strong anisotropic transient optoelectronic response of strain-engineered RuO2/TiO2 (110) heterostructures along both in-plane [001] and [1-10] crystallographic directions. Theoretical analysis identifies strain-induced modifications in band nesting as the underlying mechanism for enhanced anisotropic carrier relaxation. These findings establish epitaxial strain engineering as a powerful tool for tuning anisotropic optoelectronic responses in metallic systems, paving the way for next-generation polarization-sensitive ultrafast optoelectronic devices.
@article{arxiv.2502.08895,
title = {Anisotropic Strain Relaxation-Induced Directional Ultrafast Carrier Dynamics in RuO2 Films},
author = {S. G. Jeong and I. H. Choi and S. Lee and J. Y. Oh and S. Nair and J. H. Lee and C. Kim and A. Seo and W. S. Choi and T. Low and J. S. Lee and B. Jalan},
journal= {arXiv preprint arXiv:2502.08895},
year = {2025}
}