Weyl fermions discovered

[Charmonium]

I'm a little lost trying to understand this. I've been interested in quantum mechanics for a long time - as a lay person of course - and I've never even heard of this.

Apparently it's a quasi-particle, I guess a little like a phonon in that it doesn't have an individual existence as an actual particle but instead only exists as, I guess, a phase of matter.

This seems to be a big deal because this quasi-particle is capable of transmitting electric charge 1000x times faster than electrons in a normal semiconductor and about twice as fast as electrons in graphene.

So I'm curious as to how this qp comes into being. Is it like Cooper pairs in a superconductor or something else?

Anyway, here is one article but you can find more by googling Weyl fermion.

http://www.sciencealert.com/scienti...and-they-could-radically-speed-up-electronics

A slightly better article that basically says the same thing
http://www.gizmag.com/massless-particle-weyl-fermion-princeton/38527/

 

[disappoint]

I'm surprised you didn't try something like Princeton.edu instead of those sites you linked to that I've never even heard of.

http://www.princeton.edu/main/news/archive/S43/64/59M11/index.xml?section=topstories

 

[Charmonium]

I'm surprised you didn't try something like Princeton.edu instead of those sites you linked to that I've never even heard of.

http://www.princeton.edu/main/news/archive/S43/64/59M11/index.xml?section=topstories

A lot of that seems to be copied from whatever press release was made. There's no new info there and it certainly does nothing to explain the nature of the quasi-particle.

 

[disappoint]

A lot of that seems to be copied from whatever press release was made. There's no new info there and it certainly does nothing to explain the nature of the quasi-particle.

Really? because #1, Princeton researchers led it's discovery.

#2, One of your questions was answered in that article and you'd know that if you had bothered to read it.

This is your question from your OP:

So I'm curious as to how this qp comes into being. Is it like Cooper pairs in a superconductor or something else?

In that article I posted is this answer to it:

The crystals were then loaded into a two-story device known as a scanning tunneling spectromicroscope that is cooled to near absolute zero and suspended from the ceiling to prevent even atom-sized vibrations. The spectromicroscope determined if the crystal matched the theoretical specifications for hosting a Weyl fermion. "It told us if the crystal was the house of the particle," Hasan said.
The Princeton team took the crystals passing the spectromicroscope test to the Lawrence Berkeley National Laboratory in California to be tested with high-energy accelerator-based photon beams. Once fired through the crystal, the beams' shape, size and direction indicated the presence of the long-elusive Weyl fermion.

#3, Gizmag copied the Princeton article, not the other way around. Gizmag's is dated July 20th, 2015, The Princeton article is dated July 16th, 2015. Always go to the source. Or not, your call.

 

[Charmonium]

Really? because #1, Princeton researchers led it's discovery.

#2, One of your questions was answered in that article and you'd know that if you had bothered to read it.

This is your question from your OP:


In that article I posted is this answer to it:

That doesn't explain anything about how the particle comes into existence. It's a quasi-particle, not an actual particle. That means it's made from other states of matter. Take a look at wikipedia.

In physics, quasiparticles and collective excitations (which are closely related) are emergent phenomena that occur when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in free space. For example, as an electron travels through a semiconductor, its motion is disturbed in a complex way by its interactions with all of the other electrons and nuclei; however it approximately behaves like an electron with a different mass traveling unperturbed through free space. This "electron" with a different mass is called an "electron quasiparticle".[1] In another example, the aggregate motion of electrons in the valence band of a semiconductor is the same as if the semiconductor contained instead positively charged quasiparticles called holes. Other quasiparticles or collective excitations include phonons (particles derived from the vibrations of atoms in a solid), plasmons (particles derived from plasma oscillations), and many others.

And the information you noted was mentioned in at least one of the other articles.

edit: btw, I did read the article. Well, I skimmed it well enough to see that there was no explanation.

 

[disappoint]

Moving along, this quasi particle will be a lot more interesting once someone invents a resistor, capacitor, inductor, diode and transistor, and last but not least a cost effective source for it. Otherwise don't expect it to replace electrons anytime soon.

 

[Jeff7]

Moving along, this quasi particle will be a lot more interesting once someone invents a resistor, capacitor, inductor, diode and transistor, and last but not least a cost effective source for it. Otherwise don't expect it to replace electrons anytime soon.

Along the lines of other things that are farther along: "This new lithium-based battery could increase laptop runtimes by 8,000%."

...if development continues for the next 15 years without any surprises.

Still, it still certainly adds to our knowledge of particle physics, so :thumbsup:.

They can theoretically carry charge 1,000 times faster than ordinary electrons.

A thousand times faster? Doesn't electrical charge already move incredibly fast? As in, "a substantial percentage of the speed of light" fast?



....and is it just me, or does it look like their crazy apparatus there has a portion of it covered with aluminum foil?
I guess if the government ever switches to Weyl-based computers for surveillance, old-fashioned protection will still work.




.

 

[disappoint]

A thousand times faster? Doesn't electrical charge already move incredibly fast? As in, "a substantial percentage of the speed of light" fast?

Ordinary electrons move very slowly through a conductor actually. It's the electric field that propagates near c (the speed of light in a vacuum).

They are talking about the movement of the charge carrying particles themselves.

 

[Jeff7]

Ordinary electrons move very slowly through a conductor actually. It's the electric field that propagates near c (the speed of light in a vacuum).

They are talking about the movement of the charge carrying particles themselves.

But the drift velocity of an electron doesn't really matter, at least to a user of electricity.

When one electron so kindly nudges another one, and it in turn nudges its neighbor, and that propagates along at a very high speed, such as turning on a lightswitch and the light nearby turns on almost immediately, that's what I interpreted "carry charge" to mean.

But, maybe particle physicists and semiconductor manufacturers are concerned about it.



I'm also accustomed to many media outlets severely overstating or misinterpreting news releases from the sciences.
"New particle discovered, 1/1000th the size of a quark."
=
"Electronic devices of the future could be smaller than subatomic particles!"

 

[Charmonium]

Here's an article from Physics World that does a somewhat better job of explaining this phenomenon.

I should note that this article was available yesterday but it was impossible to get to it. I tried several times and kept getting a message that the site was down. So I'm guessing this has stimulated a lot of interest.

Now, a group headed by Zahid Hasan at Princeton University has found evidence that Weyl fermions exist as quasiparticles – collective excitations of electrons – in the semimetal tanatalum arsenide (TaAs). In 2014 Hasan and colleagues published calculations that suggested that TaAs is "Weyl semimetal". This means that TaAs should have Weyl fermions in its bulk and a distinct feature on its surface called a "Fermi arc". Using a standard technique called angle-resolved photoemission spectroscopy (ARPES), the team found evidence of a Fermi arc. The team then used a technique called soft X-ray ARPES to probe deeper into the bulk of the material, where it found further evidence for Weyl fermions in the form of "Weyl cones" and "Weyl nodes" – both of which were in agreement with the researchers previous calculations.

Fermi arcs have also been spotted in TaAs by an independent research group that includes Hongming Weng and colleagues at the Chinese Academy of Sciences. The team, which has members at the Collaborative Innovation Center of Quantum Matter in Beijing and Tsinghua University, also used ARPES in its study.

Double-gyroid crystal

Meanwhile, at the Massachusetts Institute of Technology and Zhejiang University in China, Marin Soljačić and colleagues have spotted evidence for Weyl fermions in a very different material – a "double-gyroid" photonic crystal. This crystal is made from slabs of plastic with a matrix of holes drilled in them. The slabs are then stacked in such a way that there are continuous paths through the crystal for microwave radiation to follow.

The team fired microwaves at the crystal and measured microwave transmission through the crystal while changing its orientation to the incident microwave beam – and varying the frequency of the microwaves. This allowed the researchers to map out the photonic band structure of the crystal, which reveals which microwave frequencies can travel through the crystal and which cannot. This revealed the presence of "Weyl points" in the band structure, which are indicative of Weyl fermion states existing in the photonic crystal.