the post included a link to a story titled Bose-Einstein condensate: magnetic particles behave repulsively
This is the first time I read about a magnon, a quasi-particle of magnetism.
Thank you for the moment of being enlightened. :-)
" magnons behave as weakly interacting quasiparticles obeying Bose–Einstein statistics (bosons)."
I am immediately suspicious about "quasiparticles obeying statistics."
The experiment description implies the quasiparticle was detected by a change in an electron's spin.
Because a Bose-Einstein condensate is an unusual state of matter the conclusion of this experiment has unclear (if any) consequences beyond quantum mechanics.
After this revelation of a magnon, I discovered there is also a plasmon. (!?)
a plasmon is a quantum of plasma oscillation. Just as light (an optical oscillation) consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective (a discrete number) oscillations of the free electron gas density. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton.
Until now, I did know of these other quasi-particles for quantum mechanics to explain "oscillations of the free electron gas density."
One might suspect new quasi-particles arise in quantum physics whenever the current set is lacking an explanation for a new observation or a subsequent reconsideration of that set. Without firm evidence each one remains just a place-holder proposal, until a better idea comes along. Apparently plasma presents a new challenge, needing its own quasi-particle beyond those already proposed for Maxwell's basic electromagnetism behaviors.
Just the term quasi-particle reveals it has no verifiable basis.