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Title    Researchers Discover "Excitonium"
Date    Monday December 11 2017, @03:47PM
Author    martyb
Topic   
from the hypetonium dept.
https://soylentnews.org/article.pl?sid=17/12/11/020247

takyon writes:

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.

Exciton:

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)


Original Submission

Links

  1. "takyon" - https://soylentnews.org/~takyon/
  2. "Researchers Discover Excitonium - a Weird New Form of Matter" - http://bigthink.com/paul-ratner/researchers-discover-excitonium-a-new-form-of-matter
  3. "Exciton" - https://en.wikipedia.org/wiki/Exciton
  4. "Newsweek" - http://www.newsweek.com/physics-breakthrough-new-form-matter-excitonium-finally-proved-exist-after-50-743329
  5. "Signatures of exciton condensation in a transition metal dichalcogenide" - http://science.sciencemag.org/content/358/6368/1314
  6. "DX" - https://dx.doi.org/10.1126/science.aam6432
  7. "Original Submission" - https://soylentnews.org/submit.pl?op=viewsub&subid=23750

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