Using Superconductors as Insulators 37
slambo writes "Nando Times is reporting today that Swiss scientists have discovered a way to turn a superconductor into an insulator by applying an electric current to it. " Almost zero details in the story itself, but the whole idea really appeals to me. Anyone have more details about it?
Superconductor to transistor? (Score:1)
Great, now we just need a way to change gold into lead.
Whoops: Superconductor to INSULATOR? (Score:1)
Great. I ruined THAT joke.
Re:Temperature? (Score:1)
This doesn't sound particularly New (Score:1)
Well it#s probably some interesting new design that they're really interested in.
Full text of the article (Score:4)
--Bob
Re:GdBa2Cu3O7 is a "High Tc" Superconductor (Score:1)
Superconductor/Insulator == Josephson Junction (Score:2)
Back in the 1970's IBM researchers invented the
Superconducting Josephson Junction Gate. In the
1980's IBM produced a 1ns 1kx8 ram chip that ran
at a temperature of 2.5 Kelvin.
The Josephson Junction Gate is made of a strip of
Superconducting material that has a high resistance
when it is not Superconducting. Above the gate
strip is a single turn coil of a superconducting
material that generates a field that will exceed
the critical field for the strip and turn it
non-superconducting. The Coil is connected to the
input and the gate strip is connected to the
output. The Josephson Junction Gate functions like
a field effect CMOS gate except that it switches
current instead of voltage.
Superconductor/Insulator != Josephson Junction (Score:1)
The Josephson Junctions in my lab work a little differently. A very thin (about 10^-9 m) insulator is put between two superconductors, like a sandwich. The insulator is never superconducting. If a voltage is applied across the junction (greater that 2*superconductingbandgap/e) the junction behaves like a regular ohmic resistor (V = Ir). But smaller voltages produce very fast oscillation. Its not that its an insulator, its just that the current is oscillating back and forth so fast the the net current is 0. The oscillations are something like 500GHz/Volt. This gives sort of an odd effect where if the voltage across is zero, there is on current, but if there is a voltage, the net current is zero.
Feynman does a pretty good job of this in Feynman Lectures, Vol 3, chapt 21, I think. It one of the chapeters at the end.
cya
A possible interpertation (Score:2)
It is difficult to switch temperatures back and forth quickly. but its easy to turn magnetic fields on and off quickly.
Ceramic superconductors (unlike elemental SC like lead and vanadium) are good insulators when they are above the critical temperature/magnectic field curve.
If you wrap superconductor A in a loop around SC B, passing a current through A, and the loop was small enough/current big enough, the magnetic field produced through B would cause it to become an insulator. As soon as the current was turned off, it would be a SC again. Hence a gate.
cya
Quick Overview of Superconductivity (Score:5)
At superconductor temperatures, the vibrations of the atoms slow way down and the electrons tap in to these low freq vibrational modes (called phonons, but thats not importart) causing a net attraction between electrons. Which is wierd because normally electrons repel each other.
So then the electrons pair off (into Cooper Pairs, but still not important) but these pairs are no longer fermions. (This is the important part) Instead the pairs behave as Bosons, which don't obey the Pauli exclusion principle.
All the electron pairs end up in the same lowest energy state. Now when they travel, they all travel together, but they never have to worry about finding an empty state, so they don't loose any energy.
cya
Seebeck/Peltier effect? (Score:1)
Seebeck/Peltier effect? (Score:1)
Better way of making superconduction computers (Score:1)
voltage levels like in semiconductor transistors
is not the best way to utilize superconductors.
Take a look RSFQ logic:
http://pavel.physics.sunysb.edu/RSFQ/RSFQ.html
They represent bits with quanta of magnetic flux.
A little bit more on CMOS technology (Score:3)
There are two types of CMOS transistors: NMOS and PMOS. The only difference between them is in how they are "doped" (impurity ions injected into the silicon where they lie), as one is the opposite of the other (where NMOS is doped with an electron acceptor, PMOS is doped with a electron donor and vice versa).
NMOS = n-channel metal-oxide semiconductor
PMOS = p-channel " " "
pronounced "enn-moss" and "pee-moss" (duh
Here's an easy way to think of these:
CMOS transistors have three pins. One of them is the "gate" and the other two are the source and drain, where current will either flow or not.
An NMOS transistor acts like a switch that turns "on" (closes the circuit, making a path from one switch terminal to the other), when you apply the Vcc (the voltage representing a digital "1") to the "gate", which is the top of the transistor.
A PMOS transistor works in the opposite way, conducting a current when there is a digital "0" (usually 0V) applied to the gate.
If this sparked your interest, go to a bookstore and pick up a basic digital electronics book. It'll take you through some of the related physics (which are pretty cool) and you'll learn too.
BTW, if you've ever wondered what
Interesting idea (Score:5)
The setup for creating the standard logic gates would be similar to the CMOS version and probably wouldn't take anyone longer than an hour or so to flesh out.
The advantages:
- *zero* power loss in the transistors: this means almost zero power consumption in the chip
- low-to-zero capacitance in the transistors: computers that operate at the speed of light (electrons moving as fast as physically possible)
I don't know if the switch between conductor/insulator is infitesmal or requires a fairly large time to occur, however. I guess we'll see in a few months.
Exciting technology.. any more info, anyone?
SuperConducting Insulator (Score:1)
But theoretically it would make it easier to make even FASTER processor etc
Re:A possible interpertation (Score:1)
Using the critical magnetic field to turn the gate on and off would work, but it's hardly a new phenomenon, so why would it suddenly appear as a news article?
Also, how would you produce gates of this type on a microchip? I'm not terrbily famliar with the process, but it seems that it would cause considerable difficulty to try and do this at a nanometer scale. Perhaps that is part of their "discovery"?
Re:So? (Score:1)
The telling tale will be what the energy consumption and timing is like.
Insulator... (Score:1)
Of course the idea that we can have a piece of super conducting wire insulating itself is rather nifty.
Superconductor stuff... (Score:2)
IIRC, a superconductor is impervious to magnetic fields, and also happens to freeze the magnetic field already around it when it happens to turn superconductive.
There is also a relationship that magnetic fields can induce current flow, and current flow induces magnetic fields, right? I wonder if that is the principle behind this perfect insulator; magnetic flux lines or something frozen in such a way that it actually inhibits current flow, at least in some directions.
-AS
Temperature? (Score:1)
Re:My guess (Score:1)
My guess (Score:3)
Ok, I have a physics background and one class I vaguely remember mentioned how superconductors work. If I remember correctly superconductors work because they make paths where the internal fields balance out so precisely that any electron propelled down one of these paths encounters no resistance.
This is in opposition to regular conductors where you essentially have a cloud of electrons and a field puts a net shift in the cloud, resulting in a net movement in the cloud.
My guess is that this is something like the Hall effect. The current they introduce shifts the fields around inside the superconductor itself and kills the properties that make it a superconductor.
GdBa2Cu3O7 is a "High Tc" Superconductor (Score:1)
Details? (Score:1)
'Something exciting happened. It has something to do with superconductors maybe.'
Gee, thanks. This must be what premature ejaculation is like.
Superconducting ICs already available (Score:1)
Last time I've heard about it (in 1995, at the 21st Low Temperature Physics conference), experimental samples of the superconducting integrated circuits were already built and running at 300 Gigahertz - with the 3.5 mkm technology. I only wonder what's the state of the art now, four years later.
However, the superconducting circuits are not based on conductivity switching, like the semiconductor ones - instead, they switch and exchange the magnetic flux quanta.
So what does it mean to be a superconductor, then? (Score:1)
If I understand some of the discussion here, then a superconductor stops having zero resistance as soon as you draw enough current through it, because you generate a magnetic field that screws up the superconducting properties (i.e., it gets a nonzero resistance). This seems at odds to me with some of the things they use superconductors for, like very strong magnets. Are they just using a very thick "wire" of material, to keep the internal field strength low?
This makes superconductors seem more useful for computing (low current/voltage) and less useful for things like power transistors, which was my first thought for an application when reading the blurb.
If I understand some of the other discussion here, then all they found was that if they doped a known superconductor with some other material, then they could adjust the critical temperature a few degrees by applying a current. That is a much less general result, and it makes more sense to me. Not sure what applications behavior like that has... a thermometer that works on a very narrow range, operated by bisection (numerical methods sense)?
Someone who understands the physics better, please enlighten me.
Re:Interesting idea (Score:1)
No it doesn't. Voltage at the gate is what creates the channel that allows current to flow between the source and the drain. Ok, current is needed to overcome the gate capacitance, but it's voltage which makes the switch flip.
Ironically, though, CMOS circuit designs are dominated by current considerations. That's because the gate capacitance and the capacitance of the metal wires becomes very important for ICs, so to get that required voltage change, you need to push a lot of current into those capacitors.
So I would have said:
(Ok, if that's what you meant, then I appologize. :-)
--
Re:Superconducting ICs already available (Score:1)
And what's "3.5 mkm"? Are you talking about 3.5nm? AFAIK, that's an order of magnitude smaller than the smallest semiconductors they can fabricate now, so I find it hard to believe a new technology could be made so small.
Sorry, but I'm not convinced. I think you heard wrong.
--
Room temp? (Score:1)
A way to do it (Score:1)