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Has the Mythical Unicorn of Materials Science Finally Been Found? 238

Posted by Unknown Lamer
from the even-does-the-dishes dept.
gbrumfiel writes "For years, physicists have been on the hunt for a material so weird, it might as well be what unicorn horns are made of. Topological insulators are special types of material that conduct electricity, but only on their outermost surface. If they exist, and that's a real IF, then they would play host to all sorts of bizarre phenomenon: virtual particles that are their own anti-particles, strange quantum effects, dogs and cats living together, that sort of thing. Now three independent teams think they've finally found the stuff that the dreams of theoretical physicists are made of: samarium hexaboride."
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Has the Mythical Unicorn of Materials Science Finally Been Found?

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  • by durrr (1316311) on Wednesday December 12, 2012 @11:07AM (#42261305)

    Unicornium, or Monohornium?

  • by etash (1907284) on Wednesday December 12, 2012 @11:16AM (#42261397)
    practical interesting applications for such a material ?
    • by gmuslera (3436)
      World peace was reachead at last, at least for cats and dogs. What a discovery!
      • There has been peace for cats and dogs for quite some time in my household, although it could just be a cease fire.
    • Re: (Score:2, Funny)

      by ColdWetDog (752185)

      practical interesting applications for such a material ?

      Patents. Patents. More Patents. Lawsuits.

      You know, the usual stuff.

    • Probably about as much as a material like doped silicon or germanium, which, as semiconductors, can act as electrical switches.. or amplifiers, or a few other things. On the face of it, it might not seem huge, but look how significant the invention of semiconductor material was.
      • by Rockoon (1252108)

        On the face of it, it might not seem huge, but look how significant the invention of semiconductor material was.

        Indeed, I never want to go back to a time before we had invented the 8th most common element in the universe.

    • by geekoid (135745)

      If only there was a link in the article to some sort of collaborative information source put together through a system of networks and computers.

    • Re:are there any (Score:5, Interesting)

      by slew (2918) on Wednesday December 12, 2012 @02:15PM (#42263847)

      practical interesting applications for such a material ?

      Spintronics will probably be a key practical application area. The basic idea as I understand it is that a material that exhibits strong topological insulator properties will allow for spin transport. One of the properties of topological insulators is that even in the presence of minor impurities, spin currents can be propogated quite a distance. This is apparently due to the 2d nature of the electron wavefunction on the conducting surface, the spin and the linear momentum are tightly corrolated. AFAIK, currently spintronics devices use ferromagnetic materials to create spin-coherent electric current, but apparently currents created this way have limited coherence lifetimes and thus propagation distance which limit the practical deployment.

      Another reason that this is so exciting, is that it was previously assumed that graphene conductors would be needed for spin coherent transport (graphene also have a similar 2d electron wavefunction restriction to a conducting surface), but it may turn out that manufacture of these topological insulators can be done similar to today's planar circuit fabrication techniques (which to date haven't been very applicable to creating circuits of graphene wires).

      There is also some possiblity that topological insulators this could be used in some quantum computing applications, but I haven't read any easy to digest papers on that yet.

      • by schnell (163007)
        This post is clearly extremely informative despite the fact that I did not understand any of it. But to the OP's question, though, what would some practical applications actually be?
        • Re:are there any (Score:5, Informative)

          by slew (2918) on Wednesday December 12, 2012 @07:26PM (#42267433)

          This post is clearly extremely informative despite the fact that I did not understand any of it. But to the OP's question, though, what would some practical applications actually be?

          Well, let's see if I can be a bit more specific for the typical /. user. Although there are other uses for spintronics, the current "killer" app for spintronics is high density non-volatile storage.

          The most popular user application for spintronics has been the Giant MagnetoResistive (aka GMR) read-heads used in modern disc drives to allow them to have much higher bit-density than previous generation technology. A less popular uses that may not be as familiar to the typcial /. user is the MRAM (or magneto-resistive RAM), or some magneto-resistive sensors (used in solid state compasses inside devices like cellphones and GPS car navigators).

          The underlying physics of the GMR technology is complicated, but is the result of the QM effects related to the thin layers of alternating feromagnetic materials in the read-head resulting in certain spin-statistics of the electrons in those layers. Without getting into details, the net result is that a small magnetic field can cause a giant change in resistance which can be measured (hence the name GMR) allowing much smaller magnetic domains to be used resulting in increased storage density. This is a basic application of spintronics.

          For this specific advance, it probably wouldn't be directly applicable to GMR heads, but possibly advanced spintronic based storage beyond MRAMs and racetrack memory [wikipedia.org]. Having chip interconnect that can reliably transport electron spin information will allow for much more efficient devices.

          The reason that people are looking at spintronics based storage is that in addition to the density and the non-volatile nature, the access time and durability is potentially much better than flash memory [slashdot.org]. Doing things to approach the theoretical density would be a great advance.

          Does that help?

  • by rgbrenner (317308) on Wednesday December 12, 2012 @11:25AM (#42261507)

    this sounds like an interesting article.. so why does the summary read like an april fools joke. is this the way /. encourages intelligent discussion?

    • Re: (Score:3, Funny)

      by Zeromous (668365)

      Clearly this was intended to create MASS HYSTERIA

    • by H0p313ss (811249)

      this sounds like an interesting article.. so why does the summary read like an april fools joke. is this the way /. encourages intelligent discussion?

      The quality of summaries have always varied widely depending on the submitter and editor.

      Unfortunately trying to figure out if Slashdot is dying is like trying to assess global warming by taking random temperature measurements.

    • by Chryana (708485)

      I would add to this comment that the entry on wikipedia, which is mentioned in TFA, seems so opaque to me that it might have been randomly generated and I wouldn't know any better. :(

    • by gaudior (113467)

      Why do you assume /. was ever intended to encourage intelligent discussion?

  • So it would be like steel coated porcelaine?

  • by badzilla (50355) <ultrak3wl@gPOLLOCKmail.com minus painter> on Wednesday December 12, 2012 @11:28AM (#42261543)

    I can't help feeling that "topological conductor" would be a better name for a material that behaves as an insulator in its interior but whose surface can conduct.

    • by Sockatume (732728)

      As far as I can tell, the insulating behaviour of the material arises for reasons that are related to ideas in the theory of topology. Ergo, "topological insulator". The interesting edge effects at the surface are an additional anomaly.

    • by Anonymous Coward on Wednesday December 12, 2012 @12:26PM (#42262475)

      There is actually a good reason for using "insulator" instead of "conductor". The conducting surface is a just consequence of the kind of insulating phase in the bulk rather than the central feature; it really is an kind of insulator that has conducting surface state.

      Until pretty recently most phase transitions could be traced to a breaking of symmetry, and described using something called an order parameter. Superconductivity, for example, is a consequence of breaking gauge symmetry. Topological phases, on the other hand, do *not* have an associated order parameter. They are, as you might guess from the name, distinct from trivial phases in a discrete way(and as such are robust under perturbation), and can be classified by an integer parameter.

      Topological insulators are an insulating phase that is distinct from normal insulating phases in that you cannot change to one from the other without changing it to a metal first. In a very (very) vague sense, in a topological insulator these electronic states are twisted around one another such that in order to unwind them you have to break them by making it a metal first.

      This is why the surface states are metallic. At the surface you are going from the topological phase to the trivial phase, and in order for the electronic states to unwind they have to become metallic at some point. You cannot get rid of the metallic states without destroying the topological insulating bulk phase. Furthermore, this metallic surface state will be a Dirac cone, like in graphene. So these aren't just any metallic states, they are very special ones.

      In any event, the summary is wrong. This is not the first topological insulator experimentally verified. It's just a particularly clean example, and has additional interesting wrinkles making it worth study.

      Also, if you don't like the name, it's way, way too late to hope for a change. It's been around for five years, and many thousands of papers have been written about it. Phys Rev has an RSS feed for papers on just this topic.

      • by khallow (566160)
        I don't have a complaint with the real content of the post, but I disagree with a side comment.

        Until pretty recently most phase transitions could be traced to a breaking of symmetry

        Laminar flow versus turbulent flow? Open cell versus closed cell foam? Birth and death? Solid to liquid to gas? Rough versus smooth seas? The breaking of a branch? What symmetries are being broken here?

        • So this question is, on the surface, pretty retarded. It's obvious that the terms 'phase transition' and 'symmetry' are being used as scientific jargon; your question is based on a completely different set of semantic meanings and so ultimately attempts to answer it will boil down to telling you the definition of the term and how none of your examples have anything to do with the actual subject matter.

          On the other hand, you just got a bunch of physics geeks to explain the concepts as applied to a variety of

  • by Anonymous Coward on Wednesday December 12, 2012 @11:48AM (#42261825)

    The summary includes the caveat: "If they exist, and that's a real IF".

    This is baffling, as the first topological insulators were experimentally confirmed several years ago(the family Bi2Se3, Bi2Te3, Sb2Te3, Zhang, et al. Nat Phys 5, 438 (2009)). While samarium hexaboride has some unique wrinkles in terms of physics at play, the major reason for interest is chemical. The materials above are prone the oxidation and vacancies, which shifts the fermi energy into the bulk. This means that the bulk is not fully insulating, even though the topological insulator hallmarks are still readily observable using the right experimental techniques. Samarium hexaboride appears to have a much more strongly insulating bulk, making it in some sense a much "cleaner" example.

  • IEEE July 2011 (Score:5, Informative)

    by Anonymous Coward on Wednesday December 12, 2012 @11:51AM (#42261893)

    This is a better description of Topological Insulators [ieee.org] from IEEE in July 2011. Not real sure what can be done with these things in practice. They have interesting properties, though.

  • Another use for a rare earth metal with a significant Chinese production monopoly! [criticalmetals.com]
  • I'm guessing no one noticed the bitten-apple logo laser etched on the bottom of each crystal?

  • "virtual particles that are their own anti-particles"

    You mean "bosons"? Like phonons, photons, and helium 4?

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