The “Demon” Particle: How do particles with mass become massless?

Question

I was reading an article today:
https://phys.org/news/2023-08-demon-physicists-year-old-massless-neutral.amp

…and it got me thinking. If electrons have mass and charge, how can they combine together in a metal and become massless and charge-less? Where does the mass go? I’m assuming it becomes energy because of e=mc^2, but what does that energy manifest as?

In: 0

Answer 1

This study is a bit above my pay grade, but the “demon particle” in this case is a quasiparticle which means it isn’t a particle in the sense that you are familiar with.

Because of this, “massless” also has a different meaning. I’m assuming that this refers to the effective mass of this quasiparticle which is sort of a measure of its response to external stimuli.

https://en.wikipedia.org/wiki/Effective_mass_(solid-state_physics)

Answer 2

I’m unfortunately not a material scientist, if we’re talking more than 3 particles/bodies at a time that’s not my area of expertise lol. But what I can say is that particles turn into other particles all the time. Through many, many different processes, but yeah something that has mass and charge can essentially dump its mass and charge into something else, itself turning into something charmless and massless. Now in the standard model of particle physics, there’s only one massless and chargeless particle, the photon, but maybe a material scientist can fill in what’s going on here. They’re talking about the energy bands in metal, and yeah that is far outside my area of expertise. Only discrete energy levels for me.

Answer 3

My initial read is that they’re using 2 or more energy bands of electrons, which allows the chance of electrons traveling in waves are complete counterparts. It’s not one demon electron, but 2 electrons that are in opposite waves making the total charge zero. As for massless, I’d need about 5 years to study their methodology to determine if they were accurately accounting for mass because of how small the mass of an electron is. Imagine a 200 ton pile of bricks, are you really going to feel anything adding one more brick?