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Ballistic Quantum Wires Conduct Superbly
haleos writes: "Physics Web ran an article on Ballistic Quantum Wires which allow resistance free current flow without the super-low temperatures of present-day superconductors. Just think of what a superconducting quantum wire could do for the speed of your future pocket computer!" Rather than low temperatures keeping atoms in line, these wires gain their properties from ultra-precise manufacturing techniques.
Normal conduction occurs essentially through a diffusion process where the average distance an electron travels before "hitting something" is quite low (on the order of microns to tens of microns), aka the "mean free path", or Ld in semiconductor physics equations. Ballistic conduction occurs when you find a way to increase Ld well beyond its "conventional" values over a useful distance, which is what this article claims to have done. Very cool if true!
No, the point of the article is that impurity-free wire does not need low temperatures to be superconductive.
I have heard that controlled fusion is not possible right now because the power needed to hold the magnetic bottle of fusion material (hydrogen in plasma state.) is too high. I have heard that room temp super conductors could solve this. Dose anyone have any insight on this?
Not much, since you would still need a refridgeration unit to keep the 'wire' cold. Super low means on the order of a few Kelvin. High-temp superconductors means about the same temperature of Liquid Nitrogen or better.
Did you even read the article? You don't need to keep quantum wires cold at all, just so long as the structure isn't damaged. Any old piece of wire will superconduct at low enough temperatures, that's no big deal... quantum wires here superconduct because there's no defects that lead to resistance. Nothing in the article suggests low temperatures, or mentions Cooper pairs, which are typically found in a superconductor.
For those of you who do not know, a Cooper pair is a pair of electrons whose close proximity allows their spins to cancel out, and acts as a "Boson" rather than a "Fermion." Bosons obey one sort of statistical laws, whereas Fermions obey another. Fermions have half-integer multiple spins, and bosons have whole-integer multiple spins, so combining two fermions together creates the effect of a boson. Because bosons do not follow the Pauli exclusion rule, they can all be in the same energy state, and flow through a superconductor unimpeded. The article does not mention this.
Once again, if they discovered that a tiny wire conducted electricity perfectly when very cold, that would not be news, that would be 100 year old history. It's a sorta moot point anyways, you won't be seeing this in your portable computer for a long time.
More on superconductors here.
Just my $.02
Not much, since you would still need a refridgeration unit to keep the 'wire' cold. Super low means on the order of a few Kelvin. High-temp superconductors means about the same temperature of Liquid Nitrogen or better.
A refridgeration unit in your pocket would be heavy, probably involve condensation (i.e. wet pocket), and it would emit heat.
Keeping
what these wires could do for the speed of your future pocket computer!
In my opinion, not much. The largest obstacle in the way of infinitely fast computers is the switching time of the FETs and BJTs used to make up the logic gates etc. These largely arise from the resistance, capacitance and inductance of the material in the transistors themselves, which must be made with semiconductors.
These wires are conductors (sorry for stating the obvious) and thus could not be used to fabricate a transistor using any conventional (or even known) methods. So, I'm sorry folks, but the best way to faster computers is still probably decreasing the size of the gates on the transistors.
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