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So what exactly is a Weyl fermion? Although we're often taught in high school science that the Universe is made up of atoms, from a particle physics point of view, everything is actually made up of fermions and bosons. Put very simply, fermions are the building blocks that make up all matter, such as electrons, and bosons are the things that carry force, such as photons.
Electrons are the backbone of today's electronics, and while they carry charge pretty well, they also have the tendency to bounce into each other and scatter, losing energy and producing heat. But back in 1929, a German physicist called Hermann Weyl theorised that a massless fermion must exist, that could carry charge far more efficiently than regular electrons.
And now the team at Princeton has shown that they do indeed exist. In fact, they've shown that in a test medium, Weyl electrons can carry charge at least 1,000 times faster than electrons in ordinary semiconductors, and twice as fast as inside wonder-material graphene.
Most notably, it might we be possible to build better ways to produce them en masse for further study. The strange monopole arrangement they express is still puzzling scientists, but applications may abound:
What's particularly cool about the discovery is that the researchers found the Weyl fermion in a synthetic crystal in the lab, unlike most other particle discoveries, such as the famous Higgs boson, which are only observed in the aftermath of particle collisions. This means that the research is easily reproducible, and scientists will be able to immediately begin figuring out how to use the Weyl fermion in electronics.
(Score: 3, Interesting) by VLM on Monday July 27 2015, @04:19PM
Its a common misconception of the class of the intersection of a pair of scissors a lightyear long moving 3 inches moves along the scissors at 10000x the speed of light but the pieces of scissors only move slowly.
The speed of an electrical field on or near a conductor is pretty darn fast fraction of c, but the electrons themselves move ridiculous slow like fractions of a mm if that.
Two ways to look at it.
Electroplating and electrorefining is ridiculously slow and takes insane currents to move measurable amounts of metal. Aluminum blocks being congealed electrons and stuff like that. You have to shove zillions of amps for hours to refine a chunk of copper ions. Now pushing electrons is the same deal, symmetric, its just you care about e- instead of Cu+.
The other way is a coulumb of electron charge is not really all that many electrons, compared to a chemistry number like a mole. So if an amp is a C per second... and the number of free electrons in a chunk of copper is blah per cubic centimeter (its non-trivial and has to do with how poorly some electron shells bond to their atoms as opposed to floating about in a chunk of metal) and the cross section of a DC current carrying wire, and it ends up being the average electron speed is like a bazillionth of a cm/sec. Too lazy to look it up but its gonna be "order of magnitude" like a millionth of a meter/sec if I did the math in my head right.
If you actually shoved electrons at a fraction of the speed of light, like the current in a vacuum tube, and got current densities like copper wire (yeah good luck with that LOL) then a crappy USB cable could carry something like peta-amps of current. Its interesting just how shitty of an emitter a hot thoriated tungsten cathode is, compared to a slice of copper touching another slice of copper. If you could emit electrons out of a heated cathode at metal electron density rates you'd be able to transmit amazing power levels, like star trek levels, which is probably where some of the "plasma relays" technobabble comes from, assuming a chemist or EE consulted on the show at some time.
(Score: 3, Interesting) by bd on Monday July 27 2015, @06:31PM
I can only guess, but reading the popular science in the article, I would guess they want to say electron mobility (i.e. related to resistivity) and not absolute speed of electrons.
That doesn't say electrons always have to be as slow as in the applications you mention, of course. The speed of an electron depends on the electron mobility times
the applied electric field.
Now imagine you are at just about any old pn-junction. For ease of calculation, let's say we have a potential difference of 1 V over 1 micron junction thickness,
leading to an impressive 1*10^6 V/m of field strength. Electron mobility of, say, Si is 1400 cm^2/Vs, that would lead us to 1.4*10^5 m/s for our electrons.
Now imagine a material with an electron mobility of 4*10^5 cm^2/Vs (twice the mobility of graphene, as this material claims to posess), and suddenly your
electrons actually move quite fast, even for lower field strengths. Of course, your top speed is limited by the typical saturation velocity, which is due to optical
phonon scattering and would have to be reduced as well.
That is the idea why much work has been done on high electron mobility transistors, as the maximum electron mobility limits the bandwidth of the transistors
in the multi-GHz regime. There, the idea is that one reduces scattering in the material as much as possible by separating the strongly scattering region damaged by
doping from the region where the electrons travel.
The material described in the article, on the other hand, where you actually have electrons with zero effective mass, due to the conduction band and valence
band touching each other, seems quite fascinating. This should result in a material that conducts electricity with far less resistance than the number
of defects would suggest. I admit I am not an expert on topological insulators and did not read enough to understand what actually is going on, but that is
what I guess from the band structure diagrams and some quick searching on the web.
(Score: 0) by Anonymous Coward on Tuesday July 28 2015, @04:43AM
SG-1 wasn't too far off with all of the crystalline based circuitry.
"So why do you think humans are attracted to gem stones? They were more elegant circuits, for a more civilized age! I'm not saying it was aliens, but ... it was ALIENS!"
(Score: 2) by bd on Tuesday July 28 2015, @09:55AM
Well, considering that materials such as metals and semiconductors are crystals (metals are crystals up to the grain boundary), I would guess crystalline
based circuitry is not too strange a thing. Of course, transparent crystals such as gem stones have a large band gap and are therefore insulators, not
the best material to make circuits with.