Maine farmer Posted February 9, 2016 Report Posted February 9, 2016 What exactly is quantum spin, and other than being a property of quantum particles, why does it matter? Quote
sanctus Posted February 11, 2016 Report Posted February 11, 2016 A good explanation of what it is in addition to a property is hard. The way I see it is that the particle has some angular momentum and we call this spin. There is much more to it though. I can reply better why it does matter:Easy answer first: the magnet holding your TO-Do-list on the fridge. More in detail, iron is a Ferromagnet which means that if you apply a magnetic field to it after removing it it stays (as long as it is below its Curie Temperature https://en.wikipedia.org/wiki/Curie_temperature, seeming to be at ~1k K...I always thought that one could test it at home by cooking a magnet). This property comes from the spin of the electorns, the electron like any spinning charged particle gets a magnetic dipole moment (read, as they say on wikipedia, "an electron is a tiny little magnet"). In Ferromagnets it "just" happens that all the moments align (NB: the "just" hides a lot of physics with stuff like fermion Pauli-exclusion principle etc...i.e the whole lot of quantum mechanics) creating a field that can be felt. Cool stuff: the angular moment of neutrinos have their angular momentum (spin) antiparallell to their direction of movement, anti-neutrinos have them parllalel, i.e neutrinos have only left-handed chirality anti-neutrinos have only right-handed chirality; to my understanding it is not clear yet why this is so. Very cool stuff of spin: I guess you heard of quantum entanglement? This thing where you can instantaneously affect a particle doing something to its partner entangled particle with instantaneously meaning instantaneously (but it does not break the law/axiom that it travels quicker than c, I can elaborate on that if you want). A way this is done is to partner to electrons to have opposite spins and if one is changed from up to down the other instantaneously changes from down to up; so if entangle two particles and then separate them physically they are still entangled and this spin swapping still happens not matter how far they are Quote
sanctus Posted February 11, 2016 Report Posted February 11, 2016 I did just some more research follow-up #4 says here that also below the Curie Temperature you can loose magnetism https://van.physics.illinois.edu/qa/listing.php?id=2744 Quote
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