Demonstrating Phonon Decay

Tungsten (IV) telluride (WTe2) is a very unique material with some amazing properties. I have talked before about magnetoresistance, the change in resistance of a material due to an applied magnetic field. The unique thing is that WTe2 changes its resistance by about 13 million percent and it can’t be saturated (when extra magnetic field fails change magnetisation of the material). It is also the first and only real material that constantly compensates keeping the same amount of electrons in the conduction and valence band at all times.

Recently a paper has been published looking into the vibrations in the lattice of WTe2 and the exact mechanisms behind phonons that appear there. The most interesting thing that was looked into was the transformation of optical phonons into acoustic phonons. Acoustic phonons are very similar to sound waves, thus the name, and are the atoms in the crystal vibrating from their mean position sending the wave energy thorough a system. Optical phonons are where there are two different atoms in the crystal (tungsten and tellurium in this case) that get polarised differently by light and so repel. Each pair of atoms will push out of position to get further away from their partner and it appears once the light is removed the energy that was in these optical phonons is turned into acoustic phonons. Understanding just one property of such a material could get scientists thinking about applications and eventually it could be an essential component in electronic circuits of the future.


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