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Femtosecond phase-transition in hard x-ray excited bismuth
M Makita1, I Vartiainen2, I Mohacsi2,3
1Paul Scherrer Institut, CH-5232, Villigen PSI, Switzerland. mikako.makita@xfel.eu.
Scientific Reports
|January 26, 2019
Summary
Researchers observed a novel ultrafast phase transition in bismuth crystals induced by hard X-rays. This X-ray-driven transition occurred faster than predicted by thermal models, suggesting a nonthermal lattice disordering process.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Ultrafast Phenomena
Background:
- Bismuth crystal structure evolution under optical laser excitation of A1g phonons is well-studied.
- Previous studies primarily used short pulse optical lasers to investigate these phenomena.
Purpose of the Study:
- To observe and characterize the hard X-ray induced ultrafast phase transition in a bismuth single crystal.
- To investigate the lattice dynamics and phase transition mechanism under high-intensity X-ray irradiation.
Main Methods:
- Utilized a recently developed single-shot X-ray probing setup to monitor lattice evolution.
- Employed high-intensity hard X-ray pulses (~1014 W/cm2) for excitation.
- Analyzed the time evolution of the (111) Bragg peak intensity.
Main Results:
- Observed an ultrafast phase transition in bismuth single crystals induced by hard X-rays.
- The (111) Bragg peak intensity dropped to zero within 300 fs, faster than one A1g phonon oscillation period.
- Exhibited strong dependence of lattice evolution on excitation fluence.
Conclusions:
- The observed lattice disordering process has a nonthermal origin.
- The results exclude interpretations based on electron-ion equilibration or thermodynamic heating leading to plasma formation.
- This study demonstrates a new pathway for inducing and studying ultrafast phase transitions using hard X-rays.
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