There were some big breakthroughs in superconductive materials a few years back-you can now make wire that superconducts at liquid nitrogen temperatures. Several universities have major research programs to uncover new, higher temperature superconductors.
Why don’t we have room temperature ones today? Is there a fundamental barrier to having this?
Man, imagine the benefits from this-tiny motors, MAGLEV trains, etc.
What’s going wrong?
We secretly invented them in a lab, but the Puppeteers release a bacteria that ate all of the room-tempurature superconductors on earth.
Oil companies!
The Government!
Black Helicopters!
They don’t want us to know, man!
Yeah, a breakthrough would be great, but a jump from liquid Nitrogen temp to room temp is a significant hurdle, AFAIK.
Why should we? In these levels of physics, a “breakthrough” means moving the bar down from “damn nigh impossible” to “okay, this is gonna be a bloody tough one”. Patience, m’boy.
…but Earth’s Protector has ever since been encouraging research into new room-temperature superconductors from his secret base in the Kuiper Belt! 
Seriously, I recall reading of a ceramic involving rare-earths that remained superconductive at about the CO[sub]2[/sub] freezing point – still damawful cold, but wa-a-a-ay above the <20K temperatures required for most superconductors. I don’t have facts on this, but I’d be willing to bet dollars to (Tony) doughnuts that materials scientists are studying why this ceramic remains superconductive that high in an effort to better understand how superconductivity works, with an eye to getting higher-temperature superconductors (imagine how easy it would be to use one that works at 0 F).
In the early 90’s I worked for a research company. It was an interesting* place. We had more PHDs than people with a Bachalors or less. Anyway, it was mentioned at a meeting that a span of 15-20 years between a breakthrough and the actual production of a useful product was common.
*I started to say it was a cool place. But then I would have been required to make some kind of joke referring to the <20K for regular superC and decided that would take too much effort.
Our best theories of how superconduction works are incomplete. The higher-temperature ceramic superconductors forced physicists to review just how they thought superconductivity works.
Also, we’ve discovered in recent years that the bulk properties of a material are strongly dependent on it’s exact molecular nanostructure. A room temperature superconductor may require an exact Lego-block arrangement of atoms in a material. We’re not at that level of quality control yet.
It’s possible that there are no stable superconductors at room temperature and pressure. Nobody said that has to be one, after all, just for our convenience.
The extreme difficulty of getting any piece of matter to exhibit continual superconductivity is best detailed in Robert Hazen’s book [utl=“http://www.amazon.com/exec/obidos/tg/detail/-/0345361458/qid=1107711477/sr=8-8/ref=sr_8_xs_ap_i7_xgl14/103-5432768-9311829?v=glance&s=books&n=507846”]The Breakthrough: The Race for the Superconductor. It’s about the very early days, but nothing much has really changed since.
Any conductor should theoretically become superconducting at absolute zero. The big hitch being, you can’t get there.
The low temperature superconductors become superconducting a few degrees above absolute zero. This is due to some quantum effect that I don’t understand, (electrons becoming associated into pairs and the electron pairs behave differently from individual electrons, and then I get lost) but there is at least a theoretical basis for it. These are the superconductors used in particle accelerator magnets, MRI scanners etc.
The “high” temperature superconductors become superconducting because, ah, well, we’re still not sure. There are various theories, but essentially they were discovered by accident, and much of the research into improving them has involved varying the recipes of the ceramics and seeing what happens. And if you don’t know why something works in the first place it’s hard to improve on it, especially as according to our current understanding it shouldn’t really work at all.
Since every material is a conductor to some degree, does this mean that every material would become superconducting at absolute zero?
To put this another way: There has to be some maximum temperature above which there can be no superconductors. The problem is, we have no way of knowing just what that temperature is. Maybe that temperature will be five thousand Kelvins. Maybe it’ll be 350 Kelvins. And maybe it’ll be just a little over 100 Kelvins, and we’ve already reached the limit. Really, there’s nothing physically special about room temperature, to lead us to believe that the limit should be higher than that.
You want room-temperature superconductor? I got. I show you. Five bucks.
Okay, the high Tc (critical temperature) superconductors about which I think you’re talking (ca. 1991) were called 1-2-3 superconductors because they were formulated as YBa2CuO6+x (sorry, don’t know how to do the subscripts). These were rare earth ceramics. They got Tc above LN temps. How?
The 6+x (or 7-x) part seems to be the tricky issue. Oxygen gets subtracted from the matrix in some fractional way (paraphrasing), which somehow helps electrons/holes move easily (ueber-paraphrase).
The problems of which I was aware with adapting these materials to commercial use were:
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Materials science problems. A commercial superconductor of the 1-2-3 type would probably consist of a metal wire (silver, e.g.) coated with ceramic. These can display good high Tc superconductivity on the bench (seemingly (IIRC) the current likes to flow along the outer skin of the superconductor). But the materials are very friable and not easily adapted/ducticle as are regular metal wires.
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Current problems. IIRC, many of these materials showed superconductivity loss when you tried to pump more than a little current through them (whether because of heating, lattic deformation, etc., I don’t recall specifically). Again, achieving bench superconductivity at .5 amps. is cool but not commercially very useful.
I don’t really know what’s happened with the 1-2-3 materials, or others, lately, so perhaps someone can supplement with something more than my (largely accurate but for the moment uncited) rough answers.
Aww, damn it damn it son of a biatch. Not only did I blow the subscripts, I left one out:
Try:
YBa[sub]2[/sub]Cu[sub]3[/sub]O[sub]6+x[/sub].
Might make the 1-2-3 thing (as in, the ratio of Y to Ba to Cu) more comprehensible.