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from the (sigh)-still-no-Puerto-Ricoton dept.
amblivious writes:
"Researchers investigating the creation of biexcitons noticed an unexpected drop in energy when creating multiple biexcitons in gallium arsenide, leading to the discovery of a new state of matter; the dropleton. Excitons are quasi-particles created when a photon knocks an electron loose from a material, causing an electron hole. If the forces of other charges nearby keep the electron close enough to the hole a state known as an exciton forms where the combined electron and hole act together as though they are a single particle. Biexcitons consist of two of these quasi-particles and collectively behave like a molecule. In this discovery several excitons are behaving together in a 'quantum fog' and behave like a droplet, hence the name.
See the article in Nature for more information."
(Score: -1, Offtopic) by Anonymous Coward on Monday March 03 2014, @10:02AM
the fuck-beta-on is more powerful
(Score: 5, Funny) by Ryuugami on Monday March 03 2014, @11:00AM
At first glance I read "creation of biexcitons" as "creation of biextcoins", and thought that this is yet another slightly satirical article about the newest hip Bitcoin-clone.
Luckily, I was wrong.
OTOH, their naming sense needs some work. It may behave like a droplet, but "dropleton" sounds like something a marketroid would come up with. "Buy Dropleton, It Drops Better!"
If a shit storm's on the horizon, it's good to know far enough ahead you can at least bring along an umbrella. - D.Weber
(Score: 3, Interesting) by TheSage on Monday March 03 2014, @11:22AM
I'm currently reading the (highly recommended) book "Moonshine beyond the Monster" by Terry Gannon. There, I found this gem, which seems apropriate
One of the more carefree creative outlets for mathematicians is through their happy role as nomenclators.
(Score: 3, Insightful) by Ryuugami on Monday March 03 2014, @11:32AM
Good quote, off it goes to my quote file :)
I sometimes envy people who have a sense for naming things. Mostly when naming characters in RPGs, or ship designs in space 4X games, though. If I ever discover something important, I'll likely spend more time thinking of a name then doing the actual discovery.
As the saying goes, there are two hard things in computer science: cache invalidation, naming things, and off-by-one errors.
If a shit storm's on the horizon, it's good to know far enough ahead you can at least bring along an umbrella. - D.Weber
(Score: 2, Interesting) by ls671 on Monday March 03 2014, @12:27PM
Same here. That tends to prove how easy we can get brainwashed with all that bitcoins hype lately. Well, more precisely, it is a feature of the humain brain; it will try to make something that it doesn't know look like something that it knows.
Everything I write is lies, including this sentence.
(Score: 5, Funny) by linsane on Monday March 03 2014, @12:56PM
Likewise! I can see the (as yet undiscovered) Bitcion having some very interesting properties, for example ..
- Obeys a modified version of heisenburg's uncertainty principle where the more it observed the less likely its values are to be stable
- There is a slowly increasing number of them in existence with a theoretical maximum number
- The more energy that is expended in the production of Bitcions the lower the production rate
- The Bitcion is a classical particle until it has been divided several million times to its fundamental quantum unit (satoshion?)
etc
profit?
(Score: 0) by Anonymous Coward on Monday March 03 2014, @03:28PM
"The more energy that is expended in the production of Bitcions the lower the production rate"
Actually, if you consider the acceleration of matter, the more energy that you expend to accelerate an object the less it causes it to move faster. Hence it would take an infinite amount of energy to approach the speed of light.
(Score: 1) by gishzida on Monday March 03 2014, @02:48PM
gender neutral quantum particle "intercourse"... where you get a couple of bi's excited with the natural results of dropletons your "gallium arsenide".
(Score: 2, Interesting) by keick on Monday March 03 2014, @03:17PM
Can someone please explain how this is a new state of matter, as we know it, and not just some "hey look we can create things that are missing electronics, whoppide do!"
Is this new material not a solid, liquid, gas or plasma all at the same time? Or is it just something lame like a so-quid (Wend'y Frosty). Is it not a solid in the same manor glass isn't?
Or, Occam's Razor; Some grad student did something weird with his scientific calculator and the mass turned out wrong.
(Score: 1, Informative) by Anonymous Coward on Monday March 03 2014, @03:32PM
I suppose it depends on how one defines a state of matter.
"an unexpected drop in energy when creating multiple biexcitons in gallium arsenide"
I'm guessing what they mean is that, within a phase the relationship between adding or subtracting heat and 'temperature' is approximately continuous. However, across phases, there is a discontinuity. So here by 'drop in energy' they are probably referring to a similar discontinuity.
(Score: 5, Informative) by cosurgi on Monday March 03 2014, @03:45PM
I have a pretty fresh view of that, since I just passed an exam on condensed matter physics (with best grade :). So let me tell you that exciton is a pretty amazing thingy, it is an electron-hole pair that is pretty stable. An entirely different thing than you asked. It all happens inside a crystal of GaAs. Just like diamond or silicon (which is used to make processors) is a crystal. Inside this crystal, you have about 10^23 electrons on varoius energy levels. They occupy "layers" of possible energies, just like there are orbitals in hydrogen, recall 1s, 2s, 2p thing? The same is inside a crystal, but with 10^23 electrons, not just five electrons.
And so, sometimes an electron can get kicked off from a "layer" full of 10^23 electrons. So now you have there 10^23 - 1 electrons. Pretty complex if you try to calculate it that way, with so many electrons. Much simpler to assume that you have a full layer and 1 hole in it. This hole has therefore positive charge.
The electron cannot go down in energy levels to fill the hole, because there is no available transtion in terms of wavefunctions (Shrodinger equation is involved here). So in positional coordinates they both overlap each other and coexist together. And they are attracted to each other because hole has positive charge, and electron has negative charge. The system has exactly the same hamiltonian and solution to Shrodinger's equation as if you were solving the hydrogen atom (a two particle system: in hydrogen it is proton and electron). Only the masses to plug into equation are different (the hole has an effective mass, not a real mass). But in fact it is more close to the positronium, because the effective masses of both compounds are roughly of the same order of magnitude (more interestingly you get a similar energy structure when solving a two-quark system).
So this dropleton are two negatively (electrons) and two positively (holes) charged particles, that cannot annihilate each other. Indeed that could be a molecule. I can see that indeed such a configuration would have lower energy and therefore might be stable. I am not sure what they can make of that. maybe exploit the fact that it is a boson, and infinitely many such dropletons can coexist at the same energy level, and they don't collide with each other. This could lead to some superconducting pssibilities. But it depends how many such dropletons you could make, and if you could force them to exchange (pairs of holes)/(pairs of electrons) between each dropleton, becuase only then the current could flow, I guess.
So you get a picture. This dropleton is something that happened when two electrons got kicked up into higher energy layer, from a layer full of 10^23 electrons, and those two electrons are attracted to the holes that they created, but cannot go back (for long time), because the transition has near zero probability.
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 2) by NovelUserName on Monday March 03 2014, @09:10PM
I think what the parent was asking is : "why is this a new class of matter, rather than an interesting subclass of existing matter" The reason for this question is that, to the layman, the exiton sounds like its a special subclass of matter with excited electrons- which aren't new forms of matter. Rather these are energized forms of existing matter. So the question is: why is an exiton special enough that we stop calling it an excitation state, and start calling it a new type of matter.
I at least have trouble extracting the answer from your post. Is it simply that the exiton is stable compared to the normal means by which electrons change orbitals?
(Score: 1) by cosurgi on Tuesday March 04 2014, @12:34PM
Honestly I am not sure if it is rightful to call this a "new state of matter". Maybe, and the reasoning could be following: the equations that can be used to describe exciton are exactly the same that you use to describe a single hydrogen atom in vacuum. The physical difference is that it all happens not in vacuum but in a sea of 10^23 electrons, and the hole's mass (and to be precise, electron's mass also) is a so called "effective mass".
So this is what makes it special: hydrogen atom is the simplest possible system, which has well known solutions. And you can do similar experiments, measurements & predictions on exciton to what you can do with hydrogen atom.
If they somehow manage to create 10^22 dropletons inside a crystal, then I would agree that this is a new state of matter. Because their properties would be very interesting, and maybe bizarre. Especially because they would be allowed to occupy the same energy levels (bosons). It could be similar to something what a high-temperature Bose-Einstein condensate might be if it were allowed to exists in high temperatures. But would be different enough from Bose-Einstein condensate to call it a new state of matter because: 1) high temperature, 2) inside a crystal.
A word about "high temperature". For metals, and electrons flowing there a high temperature is 50000K, but for superconductors high temperature is 50K. For this dropleton state of matter I would expect high temperature to be rather on order of 10K, but that's just a guess.
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 1) by cosurgi on Tuesday March 04 2014, @07:20PM
actually the more I think about that the more I am inclined to suspect that "high temperature" for dropletons might be around 1000K. But this is the first time I heard about them, so you can see how wild is are my guesses. If it's indeed 1000K, then it could be really interesting to investigate and may yield some useful applications.
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 1) by gottabeme on Tuesday March 04 2014, @07:02AM
I'm trying to picture this. I'm guessing the "hole" is not literally a particle. So I'm imagining an electron orbiting around a point in space, but not orbiting the point directly, rather a point offset by an imaginary pair particle, and the point of the "binary orbit" itself orbiting around the nucleus.
Is that a reasonable way to visualize it?
(Score: 1) by cosurgi on Tuesday March 04 2014, @12:19PM
In fact there is no nucleus in this picture. When you have 10^23 electrons and 10^23 nuclei our math & computers are too weak to cope with that. Therefore we assume that you have a sea of free (free from interaction with nucleus) electrons that occupy different energy layers. And this is true enough for this model to work, because when you take 10^23 atoms, and put them close enough (like they are in a crystal) then their outer electrons are free to move around between all the atoms that create the crystal (that is why you have conduction of electricity, and this particular crystal is called "metal" then). Then, similarly to the hydrogen atom, you have energy layers (aka. orbitals - but we call them layers, because each "orbital"/layer contains like 10^22 electrons (if we assume that there are 10 equally occupied layers)).
And then 1 electron goes from lower layer (with 10^22 occupied places) into higher layer (aka. an orbital with 10^22 vacant places), and wishes to go back to the hole that he created, but can't do that, because the probability of this happening is too low.
So there is no nucleus, just an electron in a sea of (10^23)-1 electrons, orbiting a hole. And this binary system has the same solutions as a hydrogen atom. The electron can occupy 1s, 2s, 2p, 3s, 3p, 3d orbits around this hole. And this electron-hole pair (called an exciton) is moving freely in the sea of electrons, and the formulas that describe their behavior are exactly similar as if it all was happening in a vacuum, not inside 10^23 electrons (the only physical difference is that a hole is impossible to create in vacuum).
Yeah, hard to explain :)
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#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
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(Score: 1) by gottabeme on Wednesday March 05 2014, @12:17AM
Thanks, that was great.
One question though--and if this is too deep for here, that's ok--but how do we "know" that, for example, the formulas are the same as for a vacuum? We can't observe individual electrons, right? So isn't this essentially an educated guess about what the electrons are doing, and a set of conclusions based upon logically extending other guesses/conclusions?
By the way, someone mod this guy up! (Probably too late now. :( )
(Score: 1) by cosurgi on Wednesday March 05 2014, @01:02AM
exactly. It is an educated guess. The only reason to think that it is exactly the same formulas is that the results agree with experimental measurements with great accuracy. If they stop agreeing, then it means that we need a new theory :)
We are not observing individual electrons here. But we can measure the extra energy level (actually all of them: 1s, 2s, 2p, ...) created by this exciton pair. We have spectrometers that have remarkable resolution, and they allow us to see those levels, just like we are observing those energy levels (using spectrometers also) in a hydrogen atom.
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(Score: 1) by cosurgi on Wednesday March 05 2014, @08:53AM
Oh, one more thing - in fact we know that this model is sometimes overly simplified. And when experimental results stop agreeing with this theory we know in fact that this is due to this simplification. There are more complex models too, which work when the simplest one stops working. Condensed matter physics is very difficult, because if you try to calculate explicitly 10^23 atoms - you are dead in the water - there is no enough computer memory. So then we are using periodic boundary conditions and many other tricks to reduce memory footprint.
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(Score: 5, Informative) by kebes on Monday March 03 2014, @03:33PM
A quasiparticle is a "collective excitation" of some other, more fundamental, particles/forces. I think the easiest one to understand is the phonon [wikipedia.org], which is a collective vibration of many atoms in a solid, which give rise to a 'localized vibration packet' that travels through the material. This becomes intuitive when you think of it in terms of sound: a sound wave travelling through air is really a bunch of gas molecules that are bumping against each other. A vibration source generates a sequence of density changes in the air, which propagate. The collective behaviour leads to a wave travelling through the air, which we call sound. In solids, phonons are the lattice vibrations that transmit sound in the solid (and in fact can be thought of as the way in which mechanical forces more generally are transmitted through the material). Coming back to quasiparticles, the crucial point is that the emergent phenomenon has properties that make it describable without worrying about (or even understanding) some of the underlying physics. So, you can model sound waves without worrying about air molecules, and even calculate their reflection, interference, etc. With phonons, we call them quasiparticles because they really do have many particle-like behaviours. They are 'effective particles', that travel with well-defined velocity, can be reflected or refracted at interfaces; these quasiparticles can even interact with each other: attracting or repelling depending on type, etc. So when physicists label something a quasiparticle, it's because the collective behaviour exhibits particle-like properties: it's a whole bunch of underlying particles that are acting in unison as a single effective entity. This not only makes it simpler to understand complex systems, but it also invariably points to some deep insights about how the system behaves.
A exciton [wikipedia.org] is a quasiparticle you get when you excite an electron in a material. The electron is knocked-out of its usual spot, leaving behind a positively-charged vacancy: an 'electron hole [wikipedia.org]'. This strongly-couple electron-hole pair (which only exists because of the excitation; i.e. energy input) has its own unique particle-like characteristics. In some cases, this exciton can separate into an electron and a hole, which are called polarons [wikipedia.org]. The 'hole' is another neat quasiparticle: it's a positive charge moving through the material, but in reality, no positive charges are moving; instead, all the negative charges (electrons) in the material are hopping around to fill the vacancy, leading to an effective motion of the positive charge. The negatively-charged polaron is also interesting: even though it's a real electron hopping around, the interaction with the medium can be thought of in terms of an 'effective electron' (whose effective mass is different from the mass of the fundamental electron particle).
Biexcitons [wikipedia.org] can arise through the interaction of two excitons. And TFA describes how they excite gallium arsenide to generate a whole bunch of excitations that all interact. Their interactions are reminiscent of a liquid (e.g. the 'pair correlation' between particle positions has the same kind of order one seems in a fluid: local preferential spacing of the particles, but long-range disroder), and so they are drawing an analogy between this collective excitation, and a small droplet of liquid.
(Score: 1) by amblivious on Monday March 03 2014, @11:49PM
Man, I'm so glad someone explained that for me ;-)
Thanks
(Score: 1) by Taibhsear on Tuesday March 04 2014, @07:45PM
This is the one part my brain was having trouble with. Thanks for clarifying. So the original electron that was excited to a higher energy level (creating the electron hole) can't just drop down to the original energy level and emit a photon (like in fluorescence, etc.) because of the sea of other electrons? And so another electron fills the first electron hole, leaving one behind themselves (the second electron hole), which yet another electron fills (creating a third hole)... Yes?
(Score: 2) by kebes on Friday March 07 2014, @01:22AM
There are various ways the excited electron can lose energy and drop back down to the ground-state, thereby eliminating both the negative and positive free charges (fluorescence being one way, thermalization being another,
(Score: 1) by waximius on Monday March 03 2014, @05:05PM
Aha! The shut down of Mt Gox makes perfect sense... not only does Uncle Sam want to control the flow of money, but he wants control over matter as well! Bastard...oh. no. I think I misread something somewhere