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Using Superconductors as Insulators
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?
Does it involve depositing a very thin and narrow layer of material so that a small current will exceed its critical current density?
This confirms my own theory. Ordinary household glass is an excellent superconductor, even at high temperatures, but the instant you apply a current -- WHOMP!! -- it becomes an insulator.
superconducting = 0 resistivity = 0 power dissipated as heat
I don't know the temp neccacary to make GdBa2Cu3O7 superconducting off the top of my head, but once you get it to that temp it shouldn't be hard to keep it there.
Here's the abstract. What it means is that a current applied to the zirconate titanate will change its polarization, which will cause the GBCO superconductor to turn into an insulator.
It's completely different from a Josephson Junction.
Abstract:
The polarization field of the ferroelectric oxide lead zirconate titanate [Pb(ZrxTi1-x)O3] was used to tune the critical temperature of the hightemperature superconducting cuprate gadolinium barium copper oxide (GdBa2Cu3O7-x) in a reversible, nonvolatile fashion. For slightly underdoped samples, a uniform shift of several Kelvin in the critical temperature was observed, whereas for more underdoped samples, an insulating state was induced. This transition from superconducting to insulating behavior does not involve chemical or crystalline modification of the material.
Well, how about using this on the new international space station. Just keep it shielded from sunlight, and it will need no extra cooling (the coolness of space will be sufficient
Posted by FascDot Killed My Previous Use:
Great, now we just need a way to change gold into lead.
Posted by FascDot Killed My Previous Use:
Great. I ruined THAT joke.
At whatever temperature the superconductor functions. If it's superconducting, it won't give off heat, as it has no resistance.
So what is this supposed to mean? A superconducting transistor? Please enlighten me, Lord...
In Soviet Russia, Jesus asks: "What Would You Do?"
*All* superconductors have a limit to their current carrying - this is because the Magnetic fields generated by the current tend to disrupt the cooper pairs. So - build a suitable supercondictive circuit and you can turn the flow of current between two points on and off...
Well it#s probably some interesting new design that they're really interested in.
--Bob
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
However, being a cuprate-oxide it is a bummer of a material to work with. Until someone figures out a reliable fabrication and processing technology then high-tc superconducting computers are just nice things to try and get grant money with. But then since I only work with metals superconducting below 1K I would say that...
This is just a Josephson Junction Gate.
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.
Thanx Doug...
I beleive this is incorrect.
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
Superconductors not only have a critical temperature, below which they are superconductors, but also critical magnetic fields, below which they are superconducting. Critical Temp is usually on the order of liquid helium (4.5deg K) for elemental superconductors, and liquid nitrogen (70 deg K) for "High Temp" ceramic supercouctors. Critical magnetic fields are something like kilogauss to Tesela.
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
Quantum Mechanics allows electrons to fill a finite number of states. Since electrons are fermions, they obey the Pauli exclusion principal: No two electrons can be in the same state at the same time. When you have a lare sample of something (like a copper wire) there are a bunch of states at the top, and most of them are unfilled. Insulators have no empty states, so there is no where for them to go. Conductors have lots of empty states, so they just glide along.
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
It's not like this is anything new. The Peltier effect seems quite similar (the use of two dissimilar semiconductors to direct heat). I read an interesting article that explains it quite well. I assume this new "insulator" is something similar, or works on the same principle.
-= PsychLo =- x86?? xor sp,sp inc sp push sp
It's not like this is anything new. The Peltier effect seems quite similar (the use of two dissimilar semiconductors to direct heat). I read an interesting article that explains it quite well. I assume this new "insulator" is something similar, or works on the same principle.
-= PsychLo =- x86?? xor sp,sp inc sp push sp
Trying to represent ones and zeroes by switching
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.
I may as well explain (very basically) how CMOS technology works, so you can get an idea.
;))
.25 micron and other numbers mean, that's basically one of the dimensions of the transistors in the chip. Smaller transistors mean less heat and faster circuits.
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
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Well, I guess the paper doesn't really explain how this can be useful. The difference between a standard transistor and a transistor I assume that would be made from this is that the logic would be controlled by unrestricted current flow, as opposed to voltage (well, *technically* standard CMOS logic relies on current, but it's essentially voltage based).
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?
æeee!
An oxymoron if I have ever heard one ...
...
But theoretically it would make it easier to make even FASTER processor etc
DONT TREAD ON ME MOÎΩN ÎABÃ
Correct me if I'm wrong, but aren't most superconductors ceramic? And don't ceramics make rather good insulators or their own. (Provided they aren't super cooled.)
Of course the idea that we can have a piece of super conducting wire insulating itself is rather nifty.
As far as I know, we don't actually have a real model to explain exactly how superconductivity works, other than intuitive guesses...
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
-AS
*Pikachu*
One big question - at what temperature would something like this run? Keeping chips cool is hard enough without having to get to superconducting temperatures!
This makes sense to me. If I remember right, the current crop of "high"-temperature superconductors are very similar to types of ceramics, which can be great insulators. Also, the superconductor theory that I remember involves pairs of electrons transiting a crystal like structure in which the "steady-state" fields were all balanced.
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.
Generally meaning that it will work effectively when chilled with liquid nitrogen. That's much better than liquid helium, but "better" is relative...
This is one of the least informative "articles" I have ever read.
'Something exciting happened. It has something to do with superconductors maybe.'
Gee, thanks. This must be what premature ejaculation is like.
"I think any time you expose vulnerabilities it's a good thing." -Attorney General Janet Reno
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.
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.
Java: the COBOL of the new millenium.
The article (more like a blurb) seems to make it out to only work with this certain superconducter operating at low temperatures. What low temperature? Liquid nitrogen? Liquid helium? What? Until it works at room temp (or at least 0 degrees celcius), don't expect it on the desktop any time soon...
Reason is the Path to God - Anon
Lets cut back on electric.The 2yk scare we'll all eat by candelight and have no money,all in banks.BULL
icey