Researchers Discover Excitonium - a Weird New Form of Matter
Excitonium, a strange form of matter that was first theorized almost 50 years ago, has now been discovered by researchers. What is excitonium? It is a rather exotic condensate that exhibits macroscopic quantum phenomena like a superconductor or a superfluid. It consists of excitons, particles formed from an unlikely pairing of an escaped electron and the hole it leaves behind. The hole actually behaves like a positively-charged particle itself. It attracts an electron and together they form the composite particle known as the exciton.
In their experiments on non-doped crystals of the transition metal dichalcogenide titanium diselenide (1T-TiSe2), the researchers were able to observe the material and its precursor soft plasmon phase, called "the smoking gun" that proves excitonium's existence. The precursor phase emerges as the material approaches its critical temperature. The scientists reproduced their results 5 times on different cleaved crystals during the testing, adding more confidence to the study.
What they achieved in particular is developing a new technique called momentum-resolved electron energy-loss spectroscopy (M-EELS) that is sensitive enough to distinguish the new material from Peierls phase, an unrelated substance that has the same symmetry.
An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and in some liquids. The exciton is regarded as an elementary excitation of condensed matter that can transport energy without transporting net electric charge.
[...] Provided the interaction is attractive, an exciton can bind with other excitons to form a biexciton, analogous to a dihydrogen molecule. If a large density of excitons is created in a material, they can interact with one another to form an electron-hole liquid, a state observed in k-space indirect semiconductors.
Additionally, excitons are integer-spin particles obeying Bose statistics in the low-density limit. In some systems, where the interactions are repulsive, a Bose–Einstein condensed state, called excitonium, is predicted to be the ground state. Some evidence of excitonium has existed since the 1970s, but has often been difficult to discern from a Peierls phase. Exciton condensates have allegedly been seen in a double quantum well systems. In 2017 Kogar et al. found "compelling evidence" for observed excitons condensing in the three-dimensional semimetal 1T-TiSe2.
Also at Newsweek.
Signatures of exciton condensation in a transition metal dichalcogenide (DOI: 10.1126/science.aam6432) (DX)
(Score: 1, Touché) by Anonymous Coward on Monday December 11 2017, @04:00PM (1 child)
This discovery is “exciting.”
(Score: 0) by Anonymous Coward on Monday December 11 2017, @07:42PM
Mix it with boron to neutralize the excitability if it creates lab risk.
(Score: 2) by drussell on Monday December 11 2017, @04:17PM (3 children)
I thought it might have been the discovery of whatever substance it is that seems to cause all those (usually) blonde sorority girls (you know, like you see in the movies) to have such high-pitched voices and an overabundance of bubbly energy overflow...
Excitonium! :)
(Score: 0) by Anonymous Coward on Monday December 11 2017, @04:29PM (2 children)
My dick is made of solid excitonium.
Shit! It just phase shifted out of existence.
(Score: 2, Informative) by Anonymous Coward on Monday December 11 2017, @04:32PM
It didn't shift out of existence, it's just so small that you need an electron microscope to find it.
(Score: 0) by Anonymous Coward on Monday December 11 2017, @09:17PM
Hello Richard. Oh, you're away now?
(Score: 2) by GreatAuntAnesthesia on Monday December 11 2017, @04:37PM (2 children)
TFS doesn't say what research lab has made this breakthrough but, based on the name the researchers gave it, I can only imagine that this amazing new form of matter was discovered by the physicists at Marvel Comics.
From this initial assumption I surmise that Excitonium has the power to grant people with invisibility, superstrength, the power of flight and/or improbably large lycra-clad boobs.
(Score: 2) by bob_super on Monday December 11 2017, @05:45PM
Marvel ? They wouldn't go for such an obvious name ... DC, maybe
(ducks)
My money would be on San Fernando Valley scientists, and the availability of many documentaries on the human effects of Excitonium on barely legal teens.
(Score: 0) by Anonymous Coward on Tuesday December 12 2017, @06:33PM
> and/or improbably large lycra-clad boobs
Where can one obtain some, for experimental purposes?
(Score: 2) by pkrasimirov on Monday December 11 2017, @05:12PM (11 children)
Somebody please translate this to layman English?
(Score: 3, Funny) by takyon on Monday December 11 2017, @05:22PM
It's exciting. Give them more funding.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 3, Interesting) by HiThere on Monday December 11 2017, @05:55PM (1 child)
After the electron is knocked off the atom it hangs around a bit before recombining with the spot it was knocked off from. Since they're calling it "excitronium" I'm going to guess they managed to knock off a whole bunch of electrons without using a heavy enough hammer to move them far enough away that they got lost (and the atoms became ions). That this could be done is quite interesting, but it's not clear what it's useful for or how stable it is without reading the article...and I probably wouldn't understand that if I did. Pumped lasers come to mind, however.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Monday December 11 2017, @07:56PM
"Pumped lasers" huh? "Honestly its not mine baby!"
(Score: 5, Informative) by maxwell demon on Monday December 11 2017, @07:27PM (6 children)
I'll try. Well, actually it's somewhat a simplification.
I assume you know what an electron is. Now electrons obey the so-called Pauli principle, that they cannot sit all in the same state. Therefore the many electrons in a solid body in the ground state (the state of lowest energy) fill up the states starting from the lowest-energy one.
Now by adding energy, you can excite an electron, that is, move it into a higher-energy state. If you do so, the state previously occupied by the electron is now free; this is referred to as a hole. Now it turns out that those holes behave very much as if they were particles of the opposite charge. In particular, electrons and holes attract each other, in the very same way an electron and a proton attract each other. Therefore there are bound states, just as with electrons and protons; with electrons and protons the bound system is known as hydrogen, while with electrons and holes it is called an exciton (because it consists of an excited electron and the hole left over from an excitation).
Quasiparticle means it behaves like a particle, but isn't really one (remember, if consists of an electron bound to a "missing electron", i.e. a hole; quite possible the very hole created in its own excitation),
The exciton carries around energy: The energy needed to excite the electron, minus the binding energy. But is is effectively uncharged because the positive and negative charges cancel out (or, in a more fundamental view, because it is just a local reorganization of the electrons).
At this point, the interaction they speak about is not the one between electron and hole, but between different excitons (there surely was something to that effect written in the cut-out part). If those excitons attract each other, then they can, again, form bound states. The bound state of two excitons is called biexciton.
Just like many water molecules can form liquid water, many excitons together can also form a liquid; an electron-hole liquid because the excitons are made of electrons and holes. Such a liquid has actually been observed in some specific type of semiconductor.
Remember what I said above about the Pauli principle? Well, that only applies to particles whose spin is a half-integer times Planck's constant (usually shortened to "half-integer spin"). The electron is such a particle, and as "missing" electron, the hole is such a particle, too. Now if you add two half-integer spins, you get an integer spin (integer-multiple of Planck's constant). Particles with integer spion don't obey the Pauli principle; quite the opposite, they prefer to be in the same state. This behaviour is called "Bose-Einstein statistics" (why they omitted Einstein in that text I have no idea). The low-density limit is because if those pairs come too close to each other, they actually "notice" that they are actually made out of individual spin-1/2 particles.
As I wrote above, integer-spin particles like to be in the same state. If they all share the same state, this is called a Bose-Einstein condensate. The repulsive interaction is probably to avoid getting them too close together. The prediction is that in some systems, such a condensate is indeed the ground state, that is, the state of minimal energy (and therefore would naturally occur). This exciton condensate is called excitonium.
People have seen something since the 1970s that might have been excitonium, but it is actually hard to distinguish excitonium from something else, called Peierls phase (don't ask me what that is), so they couldn't say for sure.
In 2017, Kogar observed something that he claims to be "compelling evidence" for such a condensate in a specific substance.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by turgid on Monday December 11 2017, @09:20PM (1 child)
And presumably knowing the amount of energy put in to put the electron into the excited state, one can calculate the probability of it falling back into the ground state emitting a packet of energy (photon?) in a give period of time?
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 3, Informative) by maxwell demon on Tuesday December 12 2017, @07:40AM
Actually you need to also know the "energy landscape" (band structure) of the material. Indeed, actually the excited electrons I've been speaking of are actually quasiparticles, too, consisting of an actual electron and the reaction of the material to the presence of that electron. Therefore it's energy-momentum relation (basically its kinetic energy) is different from that of a free electron; indeed, it can have its energy minimum at a non-zero momentum (note that the relation between momentum and speed is also affected by the material, so non-zero momentum doesn't necessarily mean non-zero speed). This is essentially what happens in the k-space indirect semiconductors mentioned in the summary: The electron and the hole have minima at different momenta, therefore in general the electron will have to get rid of some extra momentum in order to recombine with the hole. That certainly affects the probabilities.
Also note that there may be different states of same energy, but different physical properties (for example, in most materials, a spin up and a spin down quasiparticle have the same energy). The probabilities of de-excitation may be very different between those states.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 0) by Anonymous Coward on Monday December 11 2017, @09:25PM (2 children)
this was the last post on this topic when I read. I was searching for basically exactly this - an interim stage between my knowledge and domain expertise - and you provided it very well. Thank you so much, Maxwell Demon! I don't know how many others will be in the same boat, but I really appreciate your exposition!
(Score: 0) by Anonymous Coward on Monday December 11 2017, @09:36PM
PS - your last, dry line? very good :)
(Score: 2) by inertnet on Monday December 11 2017, @11:04PM
Me too. It only made sense to me after reading his remark about energy states. Uhh instantly became duh.
(Score: 2) by pkrasimirov on Tuesday December 12 2017, @05:32PM
As a layman, and on behalf of all laymen, thank you! That was actually a solid reason why "+6 Really Informative" mod should exist.
(Score: 0) by Anonymous Coward on Monday December 11 2017, @10:19PM
It is like a big ball of wibbily wobbly timey wimey...stuff
(Score: 2) by DannyB on Monday December 11 2017, @10:51PM (1 child)
Is it a good food additive?
To transfer files: right-click on file, pick Copy. Unplug mouse, plug mouse into other computer. Right-click, paste.
(Score: 0) by Anonymous Coward on Monday December 11 2017, @11:29PM
Better yet... How is it in a bong, and should I use water or strawberry Kool-Aid?