Light-Induced Subpicosecond Lattice Symmetry Switch in MoTe2

Abstract

The recent development of ultrashort laser pulses allows for optical control of structural and electronic properties of complex quantum materials. The layered transition-metal dichalcogenideMoTe2, which can crystallize into several different structures with distinct topological and electronic properties, provides possibilities to control or switch between different phases. In this study, we report a photoinduced subpicosecond structural transition between the type-II Weyl semimetal phase and normal-semimetal phase in bulk crystallineMoTe2by using ultrafast pump-probe and time-resolved second-harmonic-generation spectroscopy. The phase transition is most clearly characterized by the dramatic change of the shear oscillation mode and the intensity loss of second-harmonic generation. This work opens up new possibilities for ultrafast manipulation of the topological properties of solids, enabling potentially practical applications for a topological switch device with ultrafast excitations.

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Plain Language Summary

Intense ultrashort laser pulses are a recent development that allows researchers to control the structural and electronic properties of complex quantum materials. The layered transition-metal dichalcogenideMoTe2, which can crystallize into several different structures with distinct properties, provides possibilities to control or switch between different phases. We report on a laser-induced subpicosecond structural transition between two semimetal phases inMoTe2.

For our experiments, we use a near-infrared laser that generates femtosecond pulses 1000 times per second to trigger structural change in samples ofMoTe2and to probe those changes. We find that these pulses can indeed force a rapid transition from the type-II Weyl semimetal phase (where the valence and conduction bands cross in single points) to the normal semimetal phase.

Our experiments provide an illustration of ultrafast manipulation of the topological properties of Weyl semimetals, thus enabling potential applications for a topological switch device with ultrafast excitations.