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Graphene Continues to Surprise

I wanted to mention something on the border between chemistry and physics that might well turn out to be important. Graphene (single-layer graphite, a two-dimensional carbon sheet of fused aromatic rings) has been a hot topic for some years, but this will make it a hotter one. It is an absolute requirement that every time you write about graphene that you mention that the breakthrough in its isolation came from the use of adhesive tape, a low-tech insight at Manchester that led to a Nobel and kicked off a massive field of research. The latest is that earlier this month, a group at MIT reported that if you bring two graphene sheets together, parallel but at a slightly different rotational angle (about 1.1 degrees), that the system becomes a superconductor at low temperatures.

That was already unexpected, but the behavior of the material (electron density versus temperature) suggests some real similarities to the copper-oxide high-temperature superconductors, and no one saw that coming, either. (Note that “high temperature”, in this field, still means “can be reached in liquid nitrogen as opposed to liquid helium”). Despite a really impressive amount of theoretical and experimental work on the cuprate materials, the full details of their superconductivity are still a matter of debate. It seems to come down to Cooper pairs (as with the classic low-temperature superconductors, but the mechanism of the electron pairing is different and in ways that still start arguments. This new graphene systems might be able to shed some light on the various proposals, and you can be certain that a great deal of late-night coffee has been consumed in recent weeks to come up with appropriate experiments along these lines.

The practical value of such an understanding could well be huge (and there is, of course, another near-certain Nobel in physics waiting for whoever puts the field on a firmer basis). To give another recent MIT-related example, new superconductor engineering is at the heart of a recent announcement the university made about fusion power. The belief is that large-bore magnets of such materials, which now appear feasible, could allow a tokamak-design fusion reactor that is far more compact than any previous attempts. Wrestling with the magnets is one of the biggest problems in designing such machines, because you need extremely strong, extremely homogeneous fields. The high-temperature superconductors were recognized early on as having great possibilities in this area, but the first fusion reactor that used only these materials only became operational in 2014 (a spherical tokamak design at Tokamak Energy in the UK).

The graphene-layer materials are still operating at very low temperatures – but considering their electron density, it’s actually a lot higher than it should be. No one is going to be make fusion reactors with twisted-graphite magnets any time soon, but twisted graphite might possibly be the platform that leads us to the magnets that fusion reactors will use.

33 comments on “Graphene Continues to Surprise”

  1. kjk says:

    Is there any reason to think these would outperform other superconductors in critical field, temperature, cost, etc? Even if it is just unusual that helps basic science understand superconductivity.

  2. Dionysius Rex says:

    I bet you a million billion dollars that there are armies of Chinese currently scotch-taping graphene for 14 hours a day, 7 days a week.

    1. Me says:

      Not to mention everything else: we’ll soon have glassene, woodene, plastic-ene, and my personal favorite, chocolate brownie-ene due to these remarkable research efforts.

      1. Chester says:

        I can’t believe you missed the opportunity to make the pun “chocolate brownene”…

        1. Me says:

          I can’t actually believe that either….I have shamed my ancestors.

      2. Anon says:

        Plasticine has already been made decades ago.

        1. Me says:

          yes, but not plastic-ene – unlike chocolate brownene this one occurred to me, hence the heiphen.

    2. cheaperisntalwaysbetter says:

      No doubt they will be just as successful as the “armies of Chinese” pharma thought would fill it’s pipelines.

      1. Dionysius Rex says:

        Well, there is a slight difference between multi-parameter lead optimization and attaching a piece of sticky tape to a pencil lead…..

  3. cynical1 says:

    Will they be able to use this in the Space Force? Let’s not forget that we’re going to be going to Mars soon, as well.

  4. luysii says:

    Ah, fusion ! !

    As college freshmen we were treated to a lecture (and very impressed by) by professor Lyman Spitzer about the Stellarator, which, with just a bit of tweaking, would produce limitless energy from water. Unfortunately this was 1956.

    Such hype has led to the statement that fusion power is the energy of the future and it always will be.

    1. Anonymous says:

      Can I use the new misaligned graphene sheets as electrodes for cold fusion?
      Finally, after all these years, will we finally have “power too cheap to meter”?

  5. Barry says:

    Cheap, clean fusion power had been “thirty years away” for decades. The MIT team is so bold as to put it “fifteen years away”. But breakthroughs are notoriously hard to schedule.

    1. Isidore says:

      This is like the degrees of infinity. The set of integers smaller than the set of real numbers, but they are both infinite. Thus a continuously moving target of “fifteen years” is smaller than “thirty years”, but either appears to be infinitely away.

      1. Jeff says:

        As a sign above my desk says: “2 + 2 = 5, for sufficiently large values of 2”.

        1. dearieme says:

          Still gurgle-worthy after all these years.

    2. eub says:

      It’s like the joke(?) about “When do you expect to be done with your dissertation?” It’s “In about eighteen months” always.

      Until the student snaps and says “I have no idea.” Then it’s about eighteen months.

  6. Thoryke says:

    Meanwhile, a team has concluded that graphene could be used as hair dye: https://www.eurekalert.org/pub_releases/2018-03/nu-gfn031218.php

  7. Paul D. says:

    The ARC reactor has been getting buzz lately, but it’s worth looking at some of the details in the 2014 paper on arxiv.

    https://arxiv.org/abs/1409.3540

    The concept, which has fusion power of ~500MW(th), uses FliBe containing 90 tonnes of beryllium and ~100 tonnes of 6Li.

    The annual world production of beryllium is just 220 tonnes.

    I have seen a claim that the total US production of 6Li during the hydrogen bomb program was 442 tonnes. That production involved a facility using more than 10,000 tonnes of mercury, and that remains an environmental headache to this day.

    Perhaps those problems could be worked around (crown ethers for lithium enrichment, say), but in the end the power density of the reactor (including the volume of magnets, neutron shield, breeding tank, and vacuum vessel) is ~0.5 MW(th)/m^3, which is very low compared to a fission reactor of the same output. It’s difficult to see how this could be competitive with fission reactors, never mind the other energy sources that are driving fission out of the marketplace.

    1. Melon Usk says:

      But one can present it as ‘truly solar energy, made on Earth’ and get government subsidy

  8. BS says:

    Graphene Continues to Hype

  9. Richard Schneiderman says:

    Engineers at the Callaway Golf Co. redesigned the golf ball by using graphene as part of the ball’s outer cover. The material consists of an ultra-thin (one-atom thick) layer of hexagonal carbon that is 150 times as strong as steel on a per-pound basis, and can be stretched to up to 120% of its length without breaking or deforming. The carbon hexagons apparently flex easily but do not break. According to Callaway’s studies, the softer the golf ball, the more forgiving it is, which means it will tend to go straight and maintain speed even if you don’t hit the ball with the center of the club face.

  10. doc says:

    Check out the OnCore golf ball. Physics, not chemistry, but you can buy a dozen now.

  11. Barry says:

    And what might we observe if three (or more) sheets of graphene were stacked, each rotated 1.1degree from the one below? And how would we assemble such a thing?
    It’s long known that the forces between one sheet of graphene and another are small; that’s what makes graphite slippery. This seems a very tenuous way to assemble an electronic device, or a magnet, or anything else.

    1. luysii says:

      Things don’t move much at 1.1 Kelvin

      1. Barry says:

        but we can’t do much fabrication at 1.1k, and the coils of magnets experience large forces as they’re charged up

    2. Some idiot says:

      Lots of sticky tape… 😉

  12. Tron says:

    Des progrès très rapides sur les conditions de fonctionnement d’un réacteur à fusion permettent de donner dés aujourd’hui de chiffrer le triple produit de fusion dans un tokamak sphérique: température 180millions de degrés rayon du plasma 1,35M et puissance du champ magnétique 3.8 testa. Seuls les aimants supraconducteurs chaud (azote liquide) permettent de telles performances par rapport à l’encombrement d’un tel dispositif. Rappelons que le tokamak sphérique est beaucoup plus compact qu’un tokamak torique et ne permet pas de loger des aimants aussi volumineux.

    http://irfu.cea.fr/dacm/Phocea/Vie_des_labos/Ast/ast.php?t=fait_marquant&id_ast=4132

  13. eub says:

    What is special about 1.1 degrees? Is there something about the spatial frequency of the moire pattern that that angle gives?

    I’d love to give it a shot at a slope of phi, the “most irrational” slope angle for a lattice, just to see if that does anything.

    1. eub says:

      Hm, maybe that’s not an easy question:
      http://www.pnas.org/content/108/30/12233
      “Many properties of the moiré bands are still not understood. For example, although we are able to explain the largest magic angle analytically, the pattern of magic angles at smaller values of θ has so far been revealed only numerically. Additionally the flattening of the entire lowest moiré band at θ ≈ 1.05° remains a puzzle.”

      Related fun: twisted graphene can realize the Hofstadter butterfly fractal.
      https://arxiv.org/pdf/1101.2606.pdf

  14. Evan Schultheis says:

    I wonder what would happen if you combined this research with the paper from January that found that Graphene behaves as a P-wave superconductor when placed adjacent to Calcium atoms…

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