Anomalous Temperature-Dependent Phonon Anharmonicity and Strain Engineering of Thermal Conductivity in β-Ga2O3

& beta;-Ga2O3 is a promising candidate forhigh-performance devices such as high-power electronics, but the lowlattice thermal conductivity & kappa; seriously hinders its application.In this paper, by comparing the & kappa; at 200-700 K calculatedby the temperature-dependent and fixed second- and third-order forceconstants, the softening of optical phonons and the weakening of anharmonicitywith increasing temperature are revealed. The lattice thermal conductivityalong the crystal orientation [010] ([100] and [001]) is significantlyincreased from 23.74 W/mK (10.02 and 12.00 W/mK) to 35.58 W/mK (16.76and 18.38 W/mK) due to the application of 4% compressive uniaxialstrain along the y(z) direction.The improvement of thermal transport properties is attributed to theincrease in heat capacity, phonon group velocity, and relaxation timecaused by the decrease in volume, strengthening of polar bonds, anddecrease in three-phonon scattering channels, respectively. It isworth noting that the compression along different directions causesa change in different bond angles, which leads to the improvementor reduction of crystal symmetry and further leads to anisotropicchanges in anharmonicity. Our results pave the way for further mechanismresearch and strain engineering of thermal transport properties of & beta;-Ga2O3 and guiding novel design for theapplication of & beta;-Ga2O3-based materials.