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Physicists find particle that only has mass when moving in one direction
- isoprophlex 2y agoTitle should say "quasiparticle". The way they phrased it now, this is pretty suggestive, bordering on clickbait.
- ANarrativeApe 2y agomoving in one direction relative to what?
- xnx 2y agoTime probably
- sylware 2y ago"chirality"?
- gus_massa 2y agoNo. I had a similar idea, and the article is confusing, but it's explained near the end > "Now, at certain points the tracks intersect, so our particle train is moving along its fast track, at light speed, but then it hits an intersection and needs to switch to a perpendicular track. It's about a different effective mass for the particle in the x, y and z direction. The idea is that inside a crystal you have quasiparticles like the "holes" or the "electrons", but the "electrons" inside a crystal have a different mass that an electron movin in vacuum https://en.wikipedia.org/wiki/Effective_mass_(solid-state_physics) https://en.wikipedia.org/wiki/Effective_mass_(solid-state_ph... If the crystal is not symetrical in the x, y and z directions, it's not so weird that the "electron" (or whatever this is) has a different mass in each direction. For example crystals that are differen in the x, y and z directions may have different speed of light in each direction.
- sylware 2y agocrystal... ofc.. :(
- gus_massa 2y agoIIRC, inside iron, the magnetic field makes "electrons" with spin up and down have different band that have different curcature and then diferent effective mass. So perhaps it's possible to have a similae effect in one direction, but we should ask an expert...
- gus_massa 2y agoRetracted: IIUC the particle with spin in one direction will have a different effective mass than the particle in with dpin in the opposite direction. But they will not change mass when they change direction. (What about crystals with an asymmetric cell???)
- setopt 2y ago> What about crystals with an asymmetric cell??? Asymmetric unit cells can also cause spin-orbit coupling (e.g. Rashba effect) or altermagnetism (recently discovered effect), so it depends on the asymmetry type. The effective mass of an electron is related to d^2E(k)/dk^2 where E(k) is the electron band structure. If E(k) is linear in k_x but parabolic in k_y, the effective mass is zero in the x direction but finite in the y direction. But as far as I know, it is not possible to make the mass finite in the +x direction but zero in the -x direction.
- gus_massa 2y agoWhat happens in a half filled asymmetric band? Like https://imgur.com/a/half-filled-asymetric-band-P7NQ7zU https://imgur.com/a/half-filled-asymetric-band-P7NQ7zU A new electron will fall in places with different curvature if you choose one direction or the other. Or the mass is calculated as the average because an electric field must remove an electron form one side and put it in the oher? (I took my solid physics class too many years ago, I don't remember the details and I never understood all of them anyway.)
- gnabgib 2y agoDiscussion (16 points, 2 days ago, 7 comments) https://news.ycombinator.com/item?id=42400179 https://news.ycombinator.com/item?id=42400179
- rkagerer 2y agoThanks. That submission got flagged (presumably as clickbait). Any reason this one shouldn't too?
- sigmoid10 2y agoIt's not clickbait if you're into physics, because then the article is exactly what you'd expect. But a lot of people in the general public tend to mistake "particle" for "elementary particle" which would of course be a much bigger discovery that would not end up a side note in some blogs and instead be on the front page of every science news outlet. At least that seems to be what got people fed up in the old post's comments.
- davrosthedalek 2y agoI am a physics professor and I think this is borderline clickbait.
- fecal_henge 2y agoI really hope you prefix all your statements in life with that.
- sigmoid10 2y agoWhat kind of discovery did you expect when you clicked on the link?
- davrosthedalek 2y agoI expected it to be clickbait and be a quasi-particle.