• • Single screw dislocations in GeS nanowires reduce thermal conductivity by >50% compared to non-twisted counterparts, enabling ultralow lattice thermal conductivity for thermoelectric efficiency gains.
• • Shear strain from screw dislocations shifts AB-stacked layers by ~1/4 lattice vector along the b-axis, inducing a metastable monoclinic phase that shortens phonon lifetimes by an order of magnitude.
• • The ~200 nm diameter nanowires provide a platform to isolate dislocation-phonon interactions, but scalability to bulk materials remains unproven, with current synthesis yields <10% for single-dislocation structures.
• • Computational models predict that dislocation density of 10^10 cm^-2 could reduce thermal conductivity by 70% at 300 K, but experimental verification at such densities is lacking, posing a barrier for industrial adoption.