Unusual Electron-Phonon Interactions in Highly Anisotropic Two-Dimensional $Ta_2$$Ni_3$$Te_5$

TL;DR

This study uncovers unusual anisotropic electron-phonon interactions in quasi-one-dimensional $Ta_2Ni_3Te_5$ nano-flakes using advanced spectroscopic and theoretical techniques, revealing complex phonon behaviors and decay mechanisms.

Contribution

It demonstrates the first detailed investigation of anisotropic electron-phonon coupling in $Ta_2Ni_3Te_5$ using combined Raman spectroscopy and density functional perturbation theory.

Findings

Polarization-dependent Raman responses deviate from conventional behavior.

Observation of multi-phonon decay processes involving three- and four-phonon interactions.

Structural visualization confirms quasi-one-dimensional atomic chains as the basis for anisotropic interactions.

Abstract

Electron-phonon interactions (EPIs) represent a fundamental cornerstone of condensed matter physics, commanding persistent attention due to their pivotal role in driving novel quantum phenomena within low-dimensional materials. Here, we unveil unusual anisotropic electron-phonon coupling behaviors in quasi-one-dimensional $Ta_2$$Ni_3$$Te_5$ nano-flakes through a powerful combination of angle-resolved polarized Raman spectroscopy and density functional perturbation theory (DFPT). High-resolution transmission electron microscopy and scanning tunneling microscopy directly visualize the pronounced quasi-one-dimensional atomic chains within the crystal structure, establishing a structural foundation for the observed anisotropic interactions. Our Raman investigations reveal remarkable polarization-dependent responses in $A_g$ phonon modes that deviate significantly from conventional behavior, which our theoretical analyses attribute to complex anisotropic electron-photon and electron-phonon interactions. Temperature-dependent Raman measurements further uncover an intriguing phonon decay mechanism involving both three- and four-phonon processes, with the latter showing significant contributions in some modes - a possible manifestation of strong anisotropic electron-phonon interactions. Beyond revealing $Ta_2$$Ni_3$$Te_5$ as an exceptional platform for exploring anisotropic EPIs, this work demonstrates that integrating angle-resolved polarized Raman spectroscopy with DFPT calculations offers a powerful methodology for investigating electron-phonon interactions in emerging low-dimensional quantum materials.