| MadSci Network: Physics |
Weyl fermion *1 and massless dirac fermion (or electron) *2 both seem to be charged and massless. But what are the difference or similarity or connection between them? 1 says Weyl fermions are quasiparticles. but are massless dirac electrons also quasiparticles? (or fundamental particles?) If yes/no, "why" how? (just showing math rules are not enough, clearly show a convincing physical model).) 1 says "the particle's spin is both in the same direction as its motion" but why? because any massless fermion or boson propagating in 3D volume have its spin (+or- direction) sitting along its traveling direction? why? massless dirac electrons in *2) seem to have its leaner momentum and spin direction at 90 degree angle. Why? (why not at 0 or 180 degree? in massless particle in 3D?) because these massless particles are confined in 2D surface? Then what happens If "Weyl fermion" is also confined in 2D surface? does its momentum and spin now locked at 90 degree like massless dirac electrons in *2) instead of 0 or 180 degree in 3D? What about massless bosons in 2D? Would the angles be 0, 90, or 180 degree? why at these angles? What mechanism determine spin-momentum locking? For example, does 2D surface or masslessness put some kind of constraints on which way (transverse or longitudinal) the boson or fermion can vibrate and propagate compared to 3D? and this affects these angles? if so, why? 1)http://www.sciencealert.com/scientists-have-finally-discovered-massless-particles-and-they-could-radically-speed-up-electronics http://www.sciencemag.org/content/early/2015/07/15/science.aaa9297 2)"Success in observing the spatial distribution of massless Dirac electrons" http://www.titech.ac.jp/english/news/2014/028671.html - massless Dirac electron spin direction (at 90 degree to its traveling direction) shown on the right: http://www.riken.jp/~/media/riken/pr/press/2014/20140915_1/fig1.jpg
Re: 'Weyl fermion' 'massless dirac fermion (or electron)'difference?connection?
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