Promoting Anderson Localization for Low-Frequency Phonons in SiGe Alloyed Nanowires with Long-Range Correlated Disorder

Elucidating design principles for structures that enable phonon Anderson localization at low frequencies is crucial for applications in heat management, in thermoelectric energy harvesting, and heat-based computing technologies. Using the nonequilibrium Green's function (NEGF) method, we demonstrate that the spatial distribution of Ge with long-range correlations in SiGe nanowires significantly suppresses the transmission of low-frequency phonons (below 2 THz), breaking the Rayleigh scattering law that governs the low-frequency phonon transport in materials with point disorder, leading to a reduction in thermal conductivity by up to 60%. Importantly, these long-range spatial correlations induce phonon Anderson localization with frequencies down to 0.6 THz, with the strength being more pronounced than in randomly distributed systems. Moreover, ballistic phonons below 0.6 THz in uncorrelated structures transition to diffusive transport when spatial correlations are introduced. Our findings elucidate the heat transfer mechanisms in low-dimensional disordered systems and demonstrate possible approaches to achieving phonon Anderson localization at low frequencies.