Elastic stiffening induces one-dimensional phonons in thin DMR-2039351 TaSe; nanowires

Z. Pan, Deyu Li, K. Wang, S. H. Lee, Z. Q. Mao

Confined transport of energy carriers in low-dimensional materials could induce unusual phenomena, leading to properties promising for various applications. In the past, extensive efforts have been carried out to explore and understand thermal transport through a plethora of two- dimensional (2D) materials, while experimental studies of one-dimensional (1D) transport have been largely limited to earlier studies of thermal transport through single-walled carbon or boron nitride nanotubes. Only very recently, attempts to probe thermal transport in quasi-1D van der Waals (vdW) crystal nanowires have been made, which reveal interesting observations. Recently, Prof. Deyu Li's group at Vanderbilt University experimentally demonstrated 1D phonon-mediated thermal transport in TagSeg nanowires, which is enabled by a phonon stiffening effect. This conclusion is based on diameter dependent thermal conductivity measurement of the nanowires, with the diameter ranging from -15 to ~50 nm. Normally the thermal conductivity of (3D) phonons in nanowires would reduce with decreasing diameter. However, in the case of TagSeg nanowires, an unusual increasing trend was found when the diameter is below a certain value (~20 nm) at 300 K. This non-monotonic trend is absent at 50 K. This can only be explained by 1D phonon in the thin nanowires at 300k. The detailed findings are published in Appl. Phys. Lett. 120, 062201 (2022).