Coherent phonon dynamics at the martensitic phase transition of Ni_2MnGa

TL;DR

This study investigates the ultrafast coherent phonon dynamics during the martensitic phase transition in Ni_2MnGa using time-resolved optical reflectivity, revealing phase-specific phonons and laser-induced phase transition timescales.

Contribution

It provides new insights into phase-specific coherent phonons and demonstrates laser-induced phase transition dynamics in Ni_2MnGa.

Findings

Identification of zone-folded acoustic phonon at 1.2 THz in martensite phase

Detection of heavily damped amplitudon at 0.7 THz in pre-martensite phase

Martensitic phase transition induced by femtosecond laser pulse within a few picoseconds

Abstract

We use time-resolved optical reflectivity to study the laser stimulated dynamics in the magnetic shape memory alloy Ni_2MnGa. We observe two coherent optical phonons, at 1.2 THz in the martensite phase and at 0.7 THz in the pre-martensite phase, which we interpret as a zone-folded acoustic phonon and a heavily damped amplitudon respectively. In the martensite phase the martensitic phase transition can be induced by a fs laser pulse on a timescale of a few ps.