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Major Breakthrough In Spintronics Research
Invisible Pink Unicorn writes "Spintronics is the field of research into developing devices that rely on electron spin rather than electron charge to carry information. A major advance has been made by the Naval Research Laboratory (NRL), where they have for the first time generated, modulated, and electrically detected a pure spin current in silicon. Progress in this field is expected to lead to devices which provide higher performance with lower power consumption and heat dissipation. Basic research efforts at NRL and elsewhere have shown that spin angular momentum, another fundamental property of the electron, can be used to store and process information in metal and semiconductor based devices. The article abstract is available from Applied Physics Letters."
Now, the press release says the exciting thing about "spintronics" (ugh) is that " it frees one from the constraints of capacitive time constants and resistive voltage drops and heat buildup which accompany charge motion."
.which generates a pure spin current flowing in the opposite direction. . ."
/. article excitedly and credulously calls it?
Well, fair enough; I can readily imagine that if you could get information to flow through a magical material without having to actually make electrons move, that would be great. No more of that pesky knocking into the lattice that they do which converts their motion into heat.
But...um...how exactly do you get a spin current without the electrons actually moving? I mean, given that the spins in question are nailed to the electron? Seems tricky. Like driving down the highway without having your car move...
Furthermore, if we read further down the abstract, we find this:
"NRL scientists first inject a spin polarized electrical current. . .
Sounds to me like the existence of their spin current depends on the existence of an old-fashioned charge current. So how's this help? How is this a "key enabling advance" (as the press release calls it), still less a "major breakthrough" as the
especially if he sees the new boolean\bit implementation
On
Off
SpinNotFound
No, it's a quantum mechanical thing. Seeing spin as the electron spinning is a very intuitive picture, but also quite wrong. The real understanding of spin involves stuff like non-commuting operators that I won't go into here (and a quantum mechanics textbook will probably do it better) but the upshot is:
A single spin 1/2 particle like an electron can be in two states. You can measure the spin along x, y or z direction as you wish, and the answer will always come out to either plus or minus hbar/2. (hbar is the reduced Planck's constant).
It's with this spin like momentum and position: You can't know both at once. If you measure a certain spin along x, the spin in y and z directions will be in a Schrödinger's cat like state: Both + and - at once, but if you measure it you'll only see one. Of course you can choose an axis very close the original x, and you'll be very likely (but not sure) to measure the same general direction.
In sum, the easy thing to do with a spin is to treat it like a single bit, just pic one direction and measure along that. (For computer operation you'd probably like using 10-10000 spins at once to limit the effects of noise, just like transistors aren't quite reliable using a single electron (yet)). If you're into the advanced stuff you can have the spin hold one qubit (google it) and do quantum computation, but the technology in this particular report is likely to stay on the classical side.
Any sufficiently advanced libertarian utopia is indistinguishable from government.
Well, I'm not a particle physicist either, but I did my master's thesis on this type of system(*) So, how close are they to applications?
First of all, they've measured from 5K up to 80K which is about quarter of room temperature, practically there by solid state physics standards (see the Nature paper). Considering that the effect didn't dwindle by more than half in that range, that's a very good sign that it could be brought up to room temperature. The problem is in getting the electrons "lined up" enough. In the Nature paper they estimate that they see about 30% more spin up than down electrons, but for real applications you'd like to get a lot closer to "100% polarization". I guess that problem might be solvable, but it includes a lot of putting very thin layers of material on single crystal with quite extreme tolerances. Then again, chip fab tolerances are quite extreme already.
In cases like this it's hard to figure out how well stuff will work without actually trying, and that's what this recent paper is about: They've built a transistor-like device with technology similar to that which would be used for mass production and measured a (tiny) effect. Now it's a matter of optimisation, and they might just get there, but it'll be years at least before it's time to start drafting the chip layout.
(*) Hint: If it involves building huge accelerators to crash particles together at pseudo-Big-Bang conditions, it's particle physics. If it involves sticking little pieces of semiconductor into a magnet at 5 Kelvin it's solid state physics. Not that solid state physicists don't use particles, we're all over electrons, phonons, excitons, magnons and many other 'ons that ignorants dismiss as "quasi"particles. Hrmph!
Any sufficiently advanced libertarian utopia is indistinguishable from government.
We must move forward, not backward. Upward, not forward. And always twirling, twirling, twirling.