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Researchers see signature of “Majorana particles” inside superconducting iron
- fennecfoxen 12y agoBoth matter and antimatter? You mean like the photon and, iirc, all the other neutrally charged elementary particles? New quasi-particle is Majorana. :b
- chton 12y agoThere is more to being antimatter than just having the opposite charge. The spin of the particle also matters. For a particle to be its own antiparticle, it would have to have spin 1/2. All elementary fermions have that property, but not much else. Of the 2 classes, fermions and bosons, only fermions can be their own antiparticles. Bosons are defined with having an integer spin, so they can never have spin 1/2. Of the fermions, none are known with neutral charge except for neutrinos, and we're not sure if those are Majorana particles or not. Photons, as you mention, are bosons, with spin 1, so they can't be their own antiparticle.
- mchouza 12y agoPhotons are generally considered to be their own antiparticles: http://van.physics.illinois.edu/qa/listing.php?id=27107 http://van.physics.illinois.edu/qa/listing.php?id=27107
- chton 12y agoPhotons are something of a special case because they are massless. Gravitons, too. As bosons, their interactions are not limited by the Pauli exclusion principle, so they can not annihilate each other. They interact through different means (electromagnetic). They're both because they only have the common properties of particles and their antiparticles. It's basically like saying "the number 0 is its own negative number". It's correct according to some definitions, but not useful.
- tagrun 12y agoPhysicist here. You are confusing things. Having rest mass or Pauli-exclusion principle has nothing to do with qualification of being an anti-particle. Z boson, for instance, does have mass and is its own anti-particle. > It's basically like saying "the number 0 is its own negative number". It's correct according to some definitions, but not useful. Photons have zero charge; an anti-particle has negative of the particle's charge (and at the same time, same rest mass and spin).
- chton 12y agoAha, thanks for the correction, I must have picked up some bad info somewhere. I'll do my research better next time.
- wuliwong 12y agoI'd say that zero being it's own negative number is an important thing not to forget. :)
- acjohnson55 12y agoNeutrons are fermions with neutral charge.
- chton 12y agoExactly, and they also have spin 1/2, but we're unsure of their other properties that might make them Majorana particles.
- tagrun 12y agoThey are composite particles and we know exactly how they behave: like fermions. They are not Majorana fermions, and nothing about them is mystery. I explained how you're totally confusing things somewhere else in the thread.
- chton 12y agoMy brain added an 'I' in the middle of "neutron" in the parent comment. Probably because I was in the middle of reading something else about neutrinos :) I definitely agree that neutrons are familiar territory.
- tinyman 12y agoThere is no rule requiring antiparticles to also have spin 1/2, nor that they in general be n+1/2 spin particles (fermions). All lepton/quarks observed have half half-integer spin so there are no examples there. The SUSY sleptons/squarks would have anti-particles but integer spin if they exist, though. The W+/W- have spin 1 and are eachother's antiparticle. Z0 and the photon are their own anti particles, also spin 1. Gluons (spin 1) have anti-particles that are all another types of gluon. For composite particles, anti-deuterium and anti-helium both have integer spin. For what anti-particles actually are, I suggest looking up both C and CP conjugation.
- tagrun 12y ago> For a particle to be its own antiparticle, it would have to have spin 1/2 This is wrong. Being anti-particle has nothing to do with a particular spin. Photon is anti-photon (which by the way has spin 1).
- rprospero 12y agoThere's still a distinction between matter and anti-matter for neutral particles. For instance, the neutron and the anti-neutron are distinct, despite being neutral. They have neutral charge, but opposite baryon number. The neutron will decay into a proton by emitting and electron, while the anti-neutron will decay into an anti-proton while emitting a positron. Conservation of baryon number prevents the neutron from decaying into an anti-proton, which would otherwise make neutron sources a cheap and convenient way of producing anti-protons.
- panzi 12y agoThat's because neutrons aren't fundamental particles. They are made up of (charged) quarks.
- panzi 12y agoI literally just wanted to write the same.
- tagrun 12y ago> You mean like the photon and, iirc, all the other neutrally charged elementary particles? You are missing the point. Photon (and every such other elementary particle that annihilates itself we know) is a boson. Majorana fermion is a fermion whose anti-particle is itself. No such elementary particle exists (so far). What these people have done is a way of arranging some electrons such that they behave like Majorana fermions.
- chton 12y agoAs has been pointed out to me: ignore my previous comment. I got some fundamentals wrong and should leave the technical explanations to the real physicists :)
- chton 12y agoIt's an interesting result for solid-state physicists, but the title is very confusing to the layman. The finding is about quasi particles that have the same properties as a Majorana fermion (a Majorana bound state), due to how electrons behave in a superconductor (https://en.wikipedia.org/wiki/Majorana_fermion#Majorana_bound_states https://en.wikipedia.org/wiki/Majorana_fermion#Majorana_boun...). They did not detect a Majorana fermion itself. This is satisfactorily explained in the article, but the title is sensationalist.
- jherdman 12y ago> ... but the title is very confusing to the layman Given the density of knowledge in your comment, I'm not sure the title could be much different to aid in the understanding of the layman.
- scott_s 12y ago"New Emergent Particle Acts as its Own Anti-Particle". A layman will not know what "emergent particle" means. (I did not.) But they will at least know that the presence of an adjective implies it's not quite "a particle", and the adjective itself gives a hint to the meaning. If the layman is then piqued, they will get clarification in the article itself.
- ethbro 12y agoYou wrote the style guide for Wikipedia's mathematics articles, didn't you? ;) (By which I mean, a balance between immediate understanding vs. links for detail >> primarily links for detail without immediate understanding)
- MaysonL 12y agoWould "Virtual Particle" possibly be a more correct and explanatory term?
- scott_s 12y agoSadly, no, as "virtual particle" has a different meaning. See http://en.wikipedia.org/wiki/Virtual_particle http://en.wikipedia.org/wiki/Virtual_particle. The technical term for these, I believe is "quasiparticle": http://en.wikipedia.org/wiki/Quasiparticle http://en.wikipedia.org/wiki/Quasiparticle
- al2o3cr 12y ago(facepalm) Another day, another "popularized" article that confuses condensed-matter quasiparticles with real particles...
- acjohnson55 12y agoHonest question: If what we think of as real particles are really just useful abstractions over a more complicated reality, but that underlying reality is basically the same thing mathetmatically that exists in condensed-matter, is there a significant difference? Where does the analogy break down?
- Confusion 12y agoYes, there is a significant difference: although the quasiparticle shows the same behavior as the 'real' particle in some respects, it shows different behavior in other respects. For instance, the quasiparticle can be destroyed by the addition of some heat to the system, while a 'bare' Majorana fermion would not cease to exist in the presence of that amount of energy. Analogy: in certain measurements (e.g. distribution of reflected light frequencies), a red circle is indistinguishable from a red sphere. However, in other respects (e.g. distribution of reflected light intensity), they are quite different.
- orbifold 12y agoFrom a theorists perspective there is not much difference, they are both modeled by Quantum Field Theories. However condensed matter theory deals mostly with non-relativistic phenomena. The idea of quasiparticles, like the one they have discovered is also present in particle physics, they are called "resonances". Depending on the energy scale you can integrate out the higher energy modes of your theory to get an effective theory, in which those resonances are now the "fundamental particles", examples include pions, Kaons etc. This is analogous to how you describe quasi-particles in condensed matter theory. In contrast to condensed matter theory which is able to observe electrons on their own, the fundamental constituents in high energy particle physics have not all been observed on their own. So called quarks, the building blocks of protons and neutrons among other things, ordinarily never occur alone, due to something called confinement. This is analogous to how at low temperature in super conductors electrons appear as so called cooper pairs coupled by phonons, here quarks are in a "cosmic superconductor" coupled by gluons. One of the aims of the LHC experiment is to go to high enough energy to induce a phase transition to a quark gluon plasma, which would be analogous to the state electrons are normally in a metal. So in conclusion, it's not a coincidence that both the renormalization group by wilson and the idea for the Higgs mechanism, which also has an analogue in the theory of high temperature superconductivity and was originally proposed by Anderson in the context of condensed matter theory, were discovered by theorists working in condensed matter theory.
- kartikkumar 12y agoHere's the press announcement in 2012 of the preceeding work done in Delft: http://www.tudelft.nl/en/current/latest-news/article/detail/nanowetenschappers-vinden-langgezocht-majorana-deeltje http://www.tudelft.nl/en/current/latest-news/article/detail/.... And here's a link to the related paper on ArXiV: http://arxiv.org/abs/1204.2792 http://arxiv.org/abs/1204.2792. I know a few of the people working on the experimental setup within the Kavli Institute. Insanely complex setup! As an aerospace engineer, most of it goes well over my head, but it's interesting nonetheless!
- lnanek2 12y ago> As opposed to particles found in a vacuum, unattached to other matter, these Majoranas are what’s called “emergent particles.” They emerge from the collective properties of the surrounding matter and could not exist outside the superconductor Sounds a lot like some of the magnetic monopole announcements. It is always more of a situation than an actual thing.
- __abc 12y agoIs this a marijuana joke?
- calhoun137 12y agoThis article does demonstrate the principle that virtually every area of active research in material science, no matter how obscure, will one day have a Very Important Application in Quantum Computers. sigh