Giant in-plane vibrational and transport anisotropy in van der Waals Ta2Ni3Te5

Recently, layered van der Waals compounds of Ta2M3Te5 (M = Ni, Pd) have garnered revived interest due to their appealing potentials to host various exotic electronic states and exhibit nontrivial transport phenomena, such as the Luttinger liquid, quantum spin Hall effect, high-order topology, and superconductivity. In this paper, we report the synthesis of single-crystalline Ta2Ni3Te5 and reveal multifold in-plane anisotropic properties rooted in its quasi-one-dimensional bonding feature within each constituent layer. Our technique combines the power of polarized Raman spectroscopy, angle-resolved photoemission spectroscopy, first-principles calculations, and electrical/magneto-transport measurements. The phononic vibrations of chain-like low symmetric layered structure give rise to a highly anisotropic Raman response. The distinct intra- and inter-chain bonding characteristics lead to anisotropic dispersion of both electronic bands and acoustic phonons, which collectively result in giant in-plane mobility anisotropy (2000%) between the [100] and [001] directions, as verified by our electrical transport and Hall effect measurements. Accordingly, the transport behaviors along different in-plane directions also exhibit distinct temperature and magnetic-field dependence. The rich in-plane anisotropy revealed by the present work shows that Ta2Ni3Te5 is a promising platform for exploring novel two-dimensional anisotropic electronic dynamics with potential applications in next-generation nanoelectronic devices.