Physicists announce graphene’s latest cousin: stanene | Hacker News Reader

Physicists announce graphene’s latest cousin: stanene

nature.com

93 pointsrottyguy26 comments

They avoid mentioning this being a superconductor because it's not what it is. However having 0 resistance is a typical property of a superconductor, it's not the only defining property. I think the established defining properties of superconductors:

1. They have 0 resistance.

2. They have Meissner effect [1].

Being a topological insulator and only conducting along the edges I think (2) is not possible for this material. It's not like it makes it any less interesting.

[1] https://en.wikipedia.org/wiki/Meissner_effect

Are there any previously known zero-resistance materials without the Meissner effect?

I was sure carbon nanotubes matched your description, however the relevant Wikipedia article[1] mentions the electric properties without refering explicitly to resistance.

[1] https://en.wikipedia.org/wiki/Carbon_nanotube#Electrical_pro...

Bismuth is some weird shit. My daughter said "it looks like computers" when I showed her the crystals you can make with it. Faraday was using bismuth coils to try to unify gravity and was plotting to build anti-gravity devices with it. It's the most naturally diamagnetic element, meaning you can use it to make a magnet permanently 'float' in thin air and has one of the lowest values of thermal conductivity among metals.

It's also what makes Pepto Bismol pink.

Got a good source for bismuth?

I ordered a pound off Amazon for $24, but the supplier has it cheaper: RotoMetals.com. I would caution that even though Bismuth is considered non-toxic, there is some evidence that it will fuck up your brain temporarily. I strongly suggest heating it outside with ventilation.

Thanks!

You can precipitate bismuth from pepto bismol. There are some youtube videos showing the process.

I just pushed a button and a pound of it showed up at the house.

You can get it out of Pepto:

http://www.popsci.com/diy/article/2012-07/gray-matter-extrac...

Ah, ha! Now I know why Don A. Stuart (John W. Campbell) in the short story "Night" (1935) mentioned a bismuth coil as being part of an anti-gravity device. The device opens a time portal and sends the narrator into the far future. I just assumed Stuart's use of Bismuth was arbitrary, but now I know better.

"I hang on to your words because they are to me weighty; and where you say 'I, for my part cannot realise your dissatisfaction with the law of gravitation provided you conceive it according to your own principles' they give me great comfort. I'll have nothing to say against the law of action of gravity. It is against the law which measures its total strength as an inherent force that I venture to oppose my opinion; and I must have expressed myself badly (though I do not find the weak point) or I should not have conveyed any other impression...All I wanted to do was move men (hehe) from the unreserved acceptance of a principle of physical action which might be opposed to a natural truth. The idea that we may possibly have to connect repulsion with the lines of gravitation force (which is going far beyond anything my mind would venture on at present except in private cogitation) shows how far we may have to depart from the view I oppose." - Michael Faraday

Yeah, that's Faraday saying anti-gravity might exist, if he could only unify it with more encompassing lines of force. Note that the "hehe" is my aside. I love the part where he says "your words are weighty". :) The man was funny!

Can someone explain what it means to carry current at room temperature without any heat loss.

As a layman I interpret this as the material not having any resistance. If it does have resistance, what is that resistance generating if not heat? What happens if I put 200 amps through a thin stand of it?

"Loss" is the term we use when we want heat, but it's going away against our wishes. The correct term for generating and eliminating unwanted heat is "dissipation".

That this is the intended meaning is clear from the later wording "... being able to conduct electricity without generating any waste heat".

> What happens if I put 200 amps through a thin stand of it?

That's a good question. Even if a material can carry some small current with apparently zero R, that doesn't mean the same R value applies at a high current. It could be non-ohmic, that is.

If you want to read the details on how it works, I suggest this paper [1] "Large-gap quantum spin Hall insulators in tin films". The real hope is that this will be a replacement for the conductors in traditional silicon. You still have the heat bottleneck when you hit a traditional conductor. The dissipation free property breaks down at about 100C for this material, so you are going to have an issue with what ever is interacting with that 200A. [1] http://arxiv.org/pdf/1306.3008

I read it as meaning that it should be a superconductor. Why they do not mention it, I don't understand...

From the sound of it, you'll probably be able to transmit much lower amounts of electricity over a much longer distance in a conductor, and expend less effort sending the weak transmission.

200 amps proportional to an amount of work, measured in watts. If the wire demands less work, but you expend a constant amount of work, you'll just be sending that many more electrons to the other side of the wire. Like hitting a baseball with a baseball bat in fresh air, as opposed to under water.

I guess that means it's a super conductor, or maybe just a really good conductor? Did they say zero resistance, or only very low resistance?

First off in the scenario you're describing it makes no sense to assume a constant voltage, so you shouldn't be conflating amps and watts.

Second, the amount of watts going through a wire is not at all the same as the amount of watts being dissipated/expended in a wire. You're assuming that it's being used as a space heater, and it's not. The baseball is going through a very thin or empty environment and 99+% of the energy is still there at the other end.

Don't know about the implementation specifics, but Landauer's principle says that heat dissipation corresponds directly to information erasure. So, however they do it, it would have to be some kind of reversible circuit.

https://en.m.wikipedia.org/wiki/Landauer%27s_principle https://en.m.wikipedia.org/wiki/Reversible_computing

I interpreted the comment as quantum ballistic conduction, similar to what has been observed in carbon nanotubes and some other systems. There's resistance, but it's effectively quantised (ie, there's an integer number of quantum 'channels'). It's independent of the length of the material, so it's non-Ohmic. Which in this case effectively means other than an initial resistance of basically getting current into the quantum channel, there's no further conductive loss.

FYI - Ballistic conduction is _not_ super conductivity, as the electrons haven't paired up to form Cooper pairs via a phonon lattice distortion, the current carriers are not bosons, and doesn't display most of the other characteristics of superconductivity (eg Meissner effect).

https://en.m.wikipedia.org/wiki/Ballistic_conduction https://en.m.wikipedia.org/wiki/Conductance_quantum

Couldn't there be electromagnetic resistance too ?

So, if their predictions are correct - this is a room temperature superconductor, right?

Modeling indicates that a strip of stannene decorated with fluorine atoms at the edges may be a room temperature superconductor. Here's a link to pretty modeling pix: http://www.gizmag.com/stanene-topological-insulator/29976/

I'll try to add a link to the actual modeling paper later today, sorry but out of time right now.

This would be better if scarcity is not an issue. Carbon is abundant. Tin is not. It is even more scarce than Lithium.

So maybe we only use it for long-distance power and communications? I'm reminded of the Utopia story where, having no need of currency, they used gold for plumbing, because of its corrosion resistance.

Which isn't scarce at all.

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