Anisotropic Strain Relaxation-Induced Directional Ultrafast Carrier Dynamics in RuO2 Films

TL;DR

This paper demonstrates how anisotropic strain engineering in RuO2/TiO2 heterostructures induces directional ultrafast carrier dynamics, enabling polarization-sensitive optoelectronic responses in metallic systems.

Contribution

It introduces epitaxial strain engineering to achieve anisotropic ultrafast carrier dynamics in metals, a novel approach for polarization-sensitive optoelectronic applications.

Findings

Revealed strong anisotropic transient optoelectronic response along different crystallographic directions.

Identified strain-induced modifications in band nesting as the mechanism for anisotropic carrier relaxation.

Established epitaxial strain engineering as a tool for tuning metallic optoelectronic responses.

Abstract

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.