arXiv subjects

Guangwu Zhang

Publications and source records attributed to Guangwu Zhang.

2 recordsLinked to original sources

arXiv2026

Bending strain induced thermal conductivity suppression in freestanding BaTiO3 and SrTiO3 membranes

Freestanding perovskite oxide membranes provide a novel platform for elastic strain engineering, enabling the manipulation of phonon transport free from substrate clamping. In this work, we investigate the thermal transport properties of strontium titanate (SrTiO3) and barium titanate (BaTiO3) membranes subjected to self-formed crease induced inhomogeneous strain. By integrating spatially resolved Frequency-Domain Thermoreflectance (FDTR) with micro-Raman spectroscopy, we observe a sharp, localized suppression of thermal conductivity (k) in high-curvature regions. Specifically, k is reduced from 4.43 to 3.62 W/(m K) in SrTiO3 and from 2.27 to 1.81 W/(m K) in BaTiO3 at the crease centers, directly correlating with the local strain distribution. First-principles calculations reveal that, unlike uniform strain, the symmetry breaking induced by strain gradients significantly broadens phonon dispersion and enhances scattering rates. These findings not only elucidate the microscopic mechanisms governing phonon-strain coupling but also demonstrate the potential of inhomogeneous strain fields as a potent tool for designing dynamic solid-state thermal switches and active thermal management devices.

cond-mat.mtrl-sci↗

arXiv2025

Strain-Gradient-Driven Decoupling of Thermal Suppression from Anisotropy in \b{eta}-Ga2O3

Strain gradients, ubiquitous in flexible devices and epitaxial nanostructures, are a major blind spot for thermal transport in \b{eta}-Ga2O3. We establish that strain gradient unlocks a thermal conductivity (k) suppression mechanism fundamentally more potent than uniform strain: moderate uniaxial gradients (0.6%/nm) suppress k by 32-37% (27-30%) in thin films (nanowires), intensifying to 43.3% with biaxial gradients. This reduction far exceeds that from equivalent uniform strain and surpasses benchmark materials like silicon and BAs. Critically, a surprising decoupling emerges: while 3% uniform strain alters thermal anisotropy by ~25%, strain gradient strongly suppresses k with preserving this ratio. Mechanistically, strain gradients-induced symmetry breaking and enhanced mode coupling anisotropically activate forbidden scattering channels, making gradient-driven scattering dominant over intrinsic phonon scattering below 6.25 THz. These findings redefine non-uniform strain from a parasitic flaw into a powerful design tool for engineering thermal isolation and heat flux in next-generation flexible and high-power \b{eta}-Ga2O3 electronics.

cond-mat.mtrl-sci↗