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  1. Joined
    06 Mar '12
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    625
    19 Jan '19 10:38
    I have read this link below but am confused by an assertion it makes;

    https://phys.org/news/2019-01-insulators-edges.html

    It says;

    "...This makes it impossible for a quantum particle to be impeded, because the state of flowing in the other direction simply doesn't exist," explains Bernhard Irsigler, the first author of the study. In other words: in the edge state, the current flows without resistance. ..."


    "current flows without resistance"? So are they talking about superconductors here? If so, they didn't say so!
    But, if not, then the above assertions seem to me to directly contradict what I was taught about physics at university. Have they got it wrong? If not, can anyone show me a web-link that explains how topological insulators can result in electric current flow (along the edges) without any loss from electrical resistance but do this WITHOUT it being superconducting?

    And can anyone give me an example of a material that can conduct electrons with ZERO electrical resistance but is NOT superconductive?
    -or is that just nonsense?
    I have heard of "ballistic conduction" which can happen in NON-superconductors and results in very low electrical resistance but that STILL isn't ZERO electrical resistance!
  2. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
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    52865
    20 Jan '19 17:31
    I think they have shown zero resistance but without the exclusion of magnetic fields, the Meissner effect, shunting of magnetic fields around the superconductor.
    THAT they have not seen so it I guess by definition not real superconductivity.
    If proven out, it wouldn't matter much for the transmission of electrical energy through high voltage wires but of course the big trick is doing that at room or above temperatures. If they did, power lines would be at least 10% more efficient at getting power from one side of the country to the other.
  3. Standard memberDeepThought
    Losing the Thread
    Cosmopolis
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    27 Oct '04
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    28 Jan '19 22:19
    @humy said
    I have read this link below but am confused by an assertion it makes;

    https://phys.org/news/2019-01-insulators-edges.html

    It says;

    "...This makes it impossible for a quantum particle to be impeded, because the state of flowing in the other direction simply doesn't exist," explains Bernhard Irsigler, the first author of the study. In other words: in the edge state, t ...[text shortened]... ctors and results in very low electrical resistance but that STILL isn't ZERO electrical resistance!
    I think sonhouse has it right. A perfect conductor exhibits no resistance to current flow, a superconductor has negligible resistance and exhibits the Meissner effect. Superconductors are a subclass of (near) perfect conductors.

    They were looking at the boundary of a two dimensional insulator - so it's one dimensional. Resistance in a normal conductor is due to scattering events between the charge carriers and the lattice. In three dimensions that can be in any direction. In this the conductor is only one dimensional and for reasons the article doesn't make clear reflections (k -> -k) are ruled out, also the carrier seems not to have slower states available (k -> k' < k). Those two conditions would produce a perfect conductor, so I don't see why not, but I'd want to read the original paper before commenting further. This is more Kazet's field, maybe he can shed some light.
  4. Joined
    07 Dec '05
    Moves
    14798
    29 Jan '19 00:00
    @humy said
    I have read this link below but am confused by an assertion it makes;

    https://phys.org/news/2019-01-insulators-edges.html

    It says;

    "...This makes it impossible for a quantum particle to be impeded, because the state of flowing in the other direction simply doesn't exist," explains Bernhard Irsigler, the first author of the study. In other words: in the edge state, t ...[text shortened]... ctors and results in very low electrical resistance but that STILL isn't ZERO electrical resistance!
    This might help.

    https://phys.org/news/2018-11-two-dimensional-material-topological-insulator-superconductor.html
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