Atomic vibrations play key role in material phase change

A research group working with MAX IV’s FemtoMAX beamline has succeeded to slow the phase change from the solid to liquid state in the semiconductor, indium antimonide (InSb), by reducing the inherent vibrations between atoms. An important precursory step in the process was non-thermal melting of the sample, which broke its atomic bonds. This revealed that unbound atoms move with the velocity they had at the instant the bonds were broken. Further it showed that initial velocity is governed by atomic vibrations, which in turn are temperature dependent. The findings are steps toward functional manipulation of material structure during phase transitions.

Imagine a world where we control the structure of materials by subjecting them to short-pulse laser radiation. This is the implication of research that allows us to alter the timing when phase change occurs.

Melting a material with or without heat produces a similar result, at a similar speed. What is going on at the atomic level is quite different, however. Thermal heating excites electrons to a higher energy state. Electron-phonon coupling then equilibrates the electron and lattice temperature which makes the lattice vibrate so violently that atomic bonds break. Non-thermal heating also excites electrons but breaks the bonds instantly—within femtoseconds—and releases atoms from their original structural configuration. Scientists seek to distinguish what happens after bonds sever due to these excited electrons.

Read more on the MAX IV website

Image : FemtoMAX beamline at MAX IV