Traversing double-well potential energy surfaces: photoinduced concurrent intralayer and interlayer structural transitions in XTe2 (X=Mo, W)

TL;DR

This study investigates ultrafast photoinduced structural transitions in XTe2 (X=Mo, W), revealing simultaneous intralayer and interlayer changes that traverse double-well potential energy surfaces, with implications for symmetry engineering in quantum materials.

Contribution

It demonstrates concurrent intralayer and interlayer structural transitions in XTe2 driven by ultrafast laser excitation, revealing a pathway across double-well potential energy surfaces.

Findings

Ultrafast suppression of intralayer Peierls distortion within 0.3 ps.

Identification of twin structure and stacking faults via ultrafast structural response.

Observation of traversal of all double-well potential energy surfaces by laser excitation.

Abstract

Manipulating crystal structure and the corresponding electronic properties in quantum materials provides opportunities for the exploration of exotic physics and practical applications. Here, by ultrafast electron diffraction, structure factor calculation and TDDFT-MD simulations, we report the photoinduced concurrent intralayer and interlayer structural transitions in the Td and 1T' phase of XTe2 (X=Mo, W). Concomitant with the interlayer structural transition by shear displacement, the ultrafast suppression of the intralayer Peierls distortion within 0.3 ps is demonstrated and attributed to Mo-Mo (W-W) bond stretching. We discuss the modification of multiple quantum electronic states associated with the intralayer and interlayer structural transitions, such as the topological band inversion and the higher-order topological state. The twin structure and the stacking fault in XTe2 are identified by the ultrafast structural response. Our work elucidates the pathway of the photoinduced intralayer and interlayer structural transitions in atomic and femtosecond spatiotemporal scale. Moreover, the concurrent intralayer and interlayer structural transitions reveals the traversal of all double-well potential energy surfaces (DWPES) by laser excitation in material system, which may be an intrinsic mechanism in the field of photoexcitation-driven symmetry engineering, beyond the single DWPES transition model and the order-disorder transition model.