Elastic stiffening induces one-dimensional phonons in thin Ta₂Se₃ nanowires

Compared to extensive studies of thermal transport in two-dimensional materials, very limited attention has been paid to the corresponding phenomenon in quasi-one-dimensional van der Waals crystals. Here, we show that Ta₂Se₃ can be easily exfoliated into thin nanowires, indicating strong anisotropy in the bonding strength within the basal plane. Systematic thermal property measurements disclose signatures of one-dimensional phonons as the nanowire hydraulic diameter reduces below 19.2 nm with linearly escalating thermal conductivity as temperature increases and size dependence inconsistent with the classical size effect. We further show that these unusual transport properties are induced by elastic stiffening occurring for wires of <30 nm diameter.