Role of interlayer shear phonons on lattice symmetry switching in the transition metal dichalcogenide WTe$_{2}$

TL;DR

This study demonstrates that in WTe₂, lattice symmetry switching from T_d to 1T' phases is driven mainly by electronic excitation-induced shear sliding, independent of coherent interlayer shear phonon amplitude.

Contribution

It reveals that electronic excitation-driven shear sliding, rather than coherent phonon amplitude, governs symmetry switching in WTe₂.

Findings

Symmetry switching occurs independently of interlayer shear phonon amplitude.

Electronic excitation-driven shear sliding is the dominant mechanism.

Ultrashort pulse trains can induce structural phase transitions in 2D materials.

Abstract

Coherent phonon control using ultrashort pulse trains is the key to realizing structural phase transitions in solids by non-thermal pathways. By combining double-pulse excitation and time-resolved second harmonic generation techniques under high-density electronic excitation in a 2D layered material, WTe$_{2}$, we demonstrate that the lattice symmetry switching from the Weyl semimetallic T$_{d}$ to the semimetallic 1T$^{\prime}$ phases is independent of the amplitude of the coherent interlayer shear phonons after the arrival of the second pump pulse. This finding provides new insights into the mechanisms for symmetry switching that electronic excitation-driven shear sliding plays a dominant role.