Nanotechnology + Superconductivity = Spintronics 88
karvind writes "Spintronics is a nanoscale technology in which information is carried not by the electron's charge, as it is in conventional microchips, but by the electron's intrinsic spin and if a reliable way can be found to control and manipulate the spins spintronic devices could offer higher data processing speeds, lower electric consumption, and many other advantages over conventional chips--including, perhaps, the ability to carry out radically new quantum computations. PhysOrg is reporting that University of Notre Dame physicist Boldizsar Janko and his colleagues have found a way to achieve this control using a magnetic semiconductor, insulator and superconducting material stack of thicknesses of order of few dozen nanometers. IBM and Stanford are also looking into spintronics."
Need Wikipedia Update? (Score:5, Interesting)
Re:Need Wikipedia Update? (Score:4, Informative)
Re-read TFA where it says "Boldizsar Janko and his colleagues believe they have found such a control technique" and "Although Janko and his colleagues have tested their approach so far only through computer simulations".
Not exactly a practical, demonstrated technology yet. Wikipedia is therefore current.
Re:Need Wikipedia Update? (Score:3, Insightful)
The wikipedia article is probably referring to the specific ability to make a selective filter to pass/block currents of only a specific spin type. Or to make a transistor to amplify/switch only on a specific spin type. etc.
Spintronics and the Chinese Threat (Score:-1, Flamebait)
Spintronics? (Score:5, Funny)
Are you SURE this isn't a technology developed jointly by the press and the White House?
Re:Spintronics? (Score:2)
Re:Spintronics? (Score:0)
Microsoft in on this, too (Score:5, Funny)
Re:Microsoft in on this, too (Score:1)
DIY? (Score:2, Funny)
Re:DIY? (Score:1)
Re:DIY? (Score:0)
Re:DIY? (Score:2)
Interestingly.... no!
The electron 'spin' being discussed is a quantum mechanical property and is not the same as macroscopic rotation.
Re:DIY? (Score:4, Funny)
A fridge magnet.
(several coulombs per second) to a certain value?
A very big, precisely calibrated fridge magnet.
Re:DIY? (Score:2)
Re:DIY? (Score:3, Informative)
Not normally, no, in general.
You can find some situations where there is a difference in the energy between the two states. The most common one is the application of a magnetic field - then, the spin state that is most aligned to the field is favoured over the other one.
The other major case is in chemcial species that have partially filled orbitals. Most of these tend to have a net magnetic moment anyway, but are much more complex, and less generally applicable.
Given the presence of a magnetic field merely changes the potential landscape, no work is going to be done.
By analogy - if you want all the cars on a road to be on the left hand side - block the right hand side of the road off. Once the block is in place, no other work need be done to ensure that all the cars are on the left. (That's a sucky analogy, but it's the best I can think of).
Re:DIY? (Score:2)
The fridge is unimportant. It's the magnet that's going to affect the electron spin. The parent didn't emphasize enough that you would need a big magnet.
Not big in the sense of "Damn, this sucker is heavy." Big in the sense of "Holy Shit! I need an industrial electrical feed into my house? I need liquid nitrogen and maybe even liquid helium? Why is every piece of steel within 20 m of my magnet flying toward it at frightening speed?" That big. I won't even get started on how you detect and quantify the spins.
Re:DIY? (Score:2)
As for detecting spins, there are a multitude of ways. For instance, proton spins are detected in magnetic resonance imaging (MRI) because while the spins' orientations are affected by the external magnetic field's direction, they happen to precess about that axis like a top with a certain frequency. That frequency itself can be manipulated to generate a coherent magnetic field that alternates with time, and can be detected separately from the external field by the use of a wire coil (AC magnetic field creates a voltage that can be measured). By spatially encoding via frequency and phase (i.e. x,y,z correspond to different frequencies of alternating magnetic field, or same frequencies with phase of oscillation slightly offset per position), a map of proton density can be created (more protons = more spins = more spins). In other words, an image. THe same type of coupling is utilized in other ways, such as standard nuclear magnetic resonance, and magnetic resonance force microscopy (MRFM). The latter is basically a sort of NMR atomic force microscope. Incredibly sensitive, but a somewhat complicated setup. Last summer, a research group led by Dan Rugar was able to detect a single electron spin using and MRFM setup.
Re:DIY? (Score:3, Informative)
For free electrons there is only an energy difference in the presence of a magnetic field.
For atoms, an energy difference comes about from Zeeman splitting, which can be seen by standard textbook perturbation theory of the hydrogen atom in a magnetic field, where the otherwise degenerate levels split. This Zeeman splitting is how astronomers are able to detect the magnetic fields of astronomic objects.
Can you explain exactly what you are trying to accomplish, and why you think you need a fully polarized set of spins?
Re:DIY? (Score:3, Informative)
Re:DIY? (Score:3, Insightful)
Free electrons means without any other interactions, and spin up and spin down have no preference. In fact, the directions up/down don't mean anything unless some non-isotropic disturbance is present in the system. This would usually be the applied magnetic field.
If you have a ferromagnet, the electrons want to align parallel, so flipping one electron costs energy. This energy can come from thermal excitations, so to get the fully aligned state you need to cool the system down to minimize these excitations.
As for your battery, remember you are fundamentally storing chemical potential to drive current (actually, I'm kind of BSing here, so maybe a chemist can correct this), so aligning the spins probably won't do much. In fact, you'd most likely waste 100x or more of the energy the battery would provide just running the fridges necessary to align the spins.
But like I said, you'd really need a spintronic battery, which maybe some scientists are studying somewhere. A standard battery would lose the spin coherence relativly quickly, even if you charged it with a fully spin-polarized current.
Now about your question, if you put the spins all in spin-down state and put an up-pointing magnetic field, that's alot of energy stored there (assuming no other interactions between the spins that would allow this). But that would be very difficult to set up a state like this.
Actually such a state, if you did set it up, is at a negative temperature, believe it or not. Basically meaning there is a population inverions, with more excited states populated than ground states, and is a process fundamental to laser operation.
Re:DIY? (Score:2)
I didn't realize that the electron spin direction was the same phenomenon as the orientation of the magnetic field - is that correct? If lots of "up" electrons are conducted through a "down" permanent magnet, does that change the orientation of either the electrons or magnet, or is there potential energy in the up electrons in the down field? If the latter, does that energy force the electrons to move out of the magnetic field? And, in a final attempt to salvage this idea, what if the quanta are photons, rather than electrons - are the dynamics the same, with out the charge repulsion in the medium? Can the photon spins all be set with equipment as cheap as that for electrons?
BTW - negative temperature: that's a fascinating trip through the lookingglass
Re:DIY? (Score:4, Informative)
Quantum mechanics forces a measure of the electron's spin (and hence the direction of the dipole moment) into one of the allowable eigenstates. For a spin-1/2 fermion, such as an electron, there are only two states.
now - if you apply a field in the z direction and measure the spin in the z direction, there is a definite preference for the spin to align with the field.
if you apply the field in the y direction and measure in the z direction, then both states are of equal energies and there is no preference.
If you turn on interactions between electrons, like ferromagnetic or anti-ferromagnetic coupling, you get interesting effects, esecially at points where there the electron-electron interaction is countered by the field, and you have phase transitions at that point. if you allow for different couplings, different field directions, you can build up very rich phase diagrams of such systems, which are actually being studied by top physicists today.
Eg - anti-ferromagnetic interactions (neighbors want to be anti-aligned) on a triangle lattice is a frustrated magnet. A spin will be up, another neighbor will be down, the third is equally frustrated and doesn't know where to go. This makes very degenerate ground states, which have interesting properties.
Re:DIY? (Score:2, Informative)
Electrons placed in a magnetic field will have a potential difference between the populations aligned with and against the field, but the difference is so small that the applications at this point are severely limited.
The population difference in a 5 tesla field (the kind you need a liquid helium superconducting floor mounted magent to create and sustain) is still only a tiny fraction of the total. This population difference is utilised in ESR (Electron Spin Resonance) spectroscopy, and the spin differnce of protons is utilised in NMR (Nuclear Magnetic Resonance) spectroscopy, which is called MRI when used in medicine (because people get nervous about anything that mentions 'nuclear').
These scientists are excited because if the spin state of an electron can be controled, manipulated and stored, it presents a new pathway into the quantum computing field. This is because, as a quantum property, electron spin is affected by the same uncertainties and dualities as other quantum properties.
As to your final points, yes conducting individual electons through a permanent magnet will create the aforementioned population difference, but this will revert to a totally random population within milliseconds of being removed from the magnetic field (unless at absolute zero, but then you couldn't have current flowing anyway). I also think it unlikely that this could be used to store energy, as the energy needs to hold a sizable population of electrons in one spin orientation would rise exponentially with the population. I am also unaware of any means influence the spin orientation of photons, possibly something akin to polarising film could be employed (polarisation is a property of electromagnetic fields, and is IIRC seperate from quantum spin).
Pheew....
Re:DIY? (Score:5, Informative)
Here's a semi-serious reply to your obviously tongue-in-cheek question. I'll assume by 'certain value' you mean direction, since the total spin of an electron is fixed to hbar/2.
It depends how many spins you want to align, what percentage of the total number of spins you want to align, and how accurately you want to control the direction the spins are aligned to. In a nutshell a magnet will align the spins, cooling will also align the spins (for ferromagnets and antiferromagnets). doing both will do it faster and give more control. But that adds to the cost.
At absolute zero the slightest applied magnetic field to a paramagnetic system will line the spins entirely along the direction of the applied field.
If you get a ferromagnet, you only need to cool below the curie point and then apply a field to get the spins aligned. You'll need to go to a stronger field than above to overcome the hysteresis, though.
As someone said above, a simple refrigerator magnetic will put out weak-enough fields that will allow you to align several spins, and it will have an effect on coulombs per second if you move it fast enough. Not to high degree of polarization, but enough to attract the magnet to the refrigerator, so that should answer your question.
Re:DIY? (Score:2)
Re:DIY? (Score:3, Informative)
If you want to send a 100% polarized current of spin-up electrons into your batteries, your batteris will have a horrible coherence time and you'll eventually lose the coherence. Ie, after probably a few seconds any free electrons chosen at random from your battery will have 50% chance of being polarized up or down. Now put that battery in a magnetic field, you'll probably have more electrons of one polarity than another. but if you're not doing anything with spintronic materials or devices, this is entirely useless to you.
If you just want aligned spins, if you took a chunk of iron and cooled it sufficiently and put it in a sufficiently-high field, you can fully polarize that chunk so all the 'free' electrons point in the field direction. Of course most of the inner electrons in the iron atoms will be 'locked' into place, and unchangeable.
Re:DIY? (Score:0)
That was the lengthiest route to "refrigerator magnet", I have ever heard. My hat is off to you sir.
So, what, Base 4 Computing? (Score:3, Interesting)
Re:So, what, Base 4 Computing? (Score:1)
Still binary (Score:1)
Re:Still binary (Score:2)
Re:Still binary (Score:1)
Re:So, what, Base 4 Computing? (Score:0)
Re:So, what, Base 4 Computing? (Score:0)
Re:So, what, Base 4 Computing? (Score:1, Informative)
Re:So, what, Base 4 Computing? (Score:2, Informative)
Re:So, what, Base 4 Computing? (Score:3, Interesting)
Base four is nice because many hardware/software algorithms can be used since groups of two bits have 4 states, and a base-4 'bit' can be thought of as two independent bits.
Re:So, what, Base 4 Computing? (Score:0)
Working natively in base 4 isn't really all that useful, but if you interpret the four states as the ones needed for working natively in base 2i (which also happen to be 0, 1, 2, and 3) you can work with complex numbers trivially. Spiffy things ensue.
Re:So, what, Base 4 Computing? (Score:1)
Spintronics vs. Plasmonics (Score:1)
Mildly disappointing (Score:1, Troll)
I don't know, I guess I may as well Google spintronics at random...
Re:Mildly disappointing (Score:5, Informative)
Particles with integer spin, such as phonons (spin 0), photons (spin 1), gravitons (spin 2) are called Bosons and obey Bose-Einstein statistics. Any number of bosons can be found in any quantum state, and at low temperatures they can condense into the ground state via Bose-Einstein Condensation.
Particles with half-integer spin, such as electrons, protons, neutrons (all spin 1/2) are called Fermions, and obey Fermi-Dirac statistics. This means interchanging two fermions in a system will cause the wavefunction of the system to acquire a factor of negative one. So if two fermions are in the same quantum state, that component of the wavefunction must be equal to it's negative - meaning zero. This is the Pauli Exclusion Principle, meaning no two fermions can ever exist in the same quantum state of a system. This effect has profound impact on physics, accounting for orbital nature of atoms, band structure of semiconductors, etc.
Anyway, back to your question about spin, another aspect of spin is that the allowable spin values must differ by integer units of hbar. So electrons, with total spin of hbar/2 are allowed two states that differ by hbar - +hbar/2 and -hbar/2. Usually the direction is chosen by an applied field, or whatever direction is chosen to measure the electron spin.
Spin is tricky because it isn't simply additive, but follows appropriate group theory. Electrons are part of SU(2) algebra, and spin interactions are weird. For example, you can simultaneously know the total spin (electrons are always hbar/2) and the spin component along one direction (for electrons this could be +hbar/2 and -hbar/2). But you cannot know the x, y, and z components simultaneously, basically because the Pauli matrices don't commute (Heisenberg uncertainty principle). So in actuality a spin-up electron really points somewhere along a cone that mostly points up, but you don't know more than that.
With two electrons, you can simultaneously know EITHER the total spin of the pair AND the total spin projected along one axis, OR you can know the projections of the two independent spins along one axis. If one electron is up and another is down, the system is in a state of 1/sqrt(2) (spin-Zero + spin-One). Also - this means that the two-electron system can exist in a Spin-1 state with the spin in one direction zero, or a Spin-0 also with the spin in one direction zero. Since the two electrons would have an integral number of spin, the system acts like a Boson. This is what allows superconductors, which are mentioned in TFA, to pair up and effectively condense.
Additionally, the spin-zero state of two electronss is very important in quantum communication, quantum teleportation, and quantum computation. This is the state with total spin zero, so no matter what direction you measure one spin, the other spin is aligned opposite.
Re:Mildly disappointing (Score:3, Informative)
Oddly enough, free electrons do not have well-defined spin directions (interference phenomena destroy any possibility of measuring it, so it does not exist). Because of this it is not the case that electron-spin correlation is important to quantum communciation. Photon linear polarization alignment in J=0 states, which is the spin-1 analogue of the spin-zero state of two free electrons, is important, though. And bound electrons do have well-defined spin directions, which is what creates interesting effects in superconductors etc.
--Tom
Re:Mildly disappointing (Score:2, Insightful)
Scientific American [sciam.com] (warning: loaded with ads etc)
Not for the light-hearted, a thorough review in Reviews of Modern Physics [aip.org] (subscription required, if you cannot access the article, drop me an email at karvind@NOSPAM.gmail.com)
On Ferroelectric spintronics [colossalstorage.net] from Colossal Storage.
Spintronics and Quantum Dots [unibas.ch]. Discussion about one possible implementation.
Another good introduction [aist.go.jp].
Hope it helps.
And room-temperature superconductors too (Score:0)
There is a limit to how much of a system you can simulate while still retaining a semblance to practical reality. Spintronics seems to exceed it.
And on top of that, even if it worked, it would be susceptible to interference from external magnetic fields, which are far harder to shield against than the electric ones that can create interference in our existing electronic systems. (Interference by magnetic induction is only a minor secondary susceptibility in electronics.)
Where spintronics get really silly though is in its need for nanotechnology. Once we have nanotech, there will be no need for spin manipulation at all, since you'll be able to build mnechanical computers with trillions of times our current MIPs using elementary principles that have been very widely documented in the nanotech literature.
Ha (Score:-1, Offtopic)
I'm positive
Re:Ha (Score:0)
Atom to another atom:
I lost an electron!
Are you sure?
I'm positive.
Lots of research (Score:5, Informative)
Spintronics also represents one of the quickest transitions from lab to market, next to the transistor via GMR sensors. The hard disk read heads on the hard drives in your computer, if you bought a new disk in the past few years, already incorporates spintronic effects through GMR (Giant MagnetoResistance). Most major media storage and also electronics companies have been heavily investigating spintronics for years too, not to mention a good percentage of condensed-matter physicsists, electrical and materials-science engineers.
Spintronics is also being investigated for quantum computation because the two electron eigenstates in any direction (up / down) can make a good basis for the Zero and One states of a qubit.
But to repeat the hype, spintronics does have potential to revolutionize the electronics industry by offering a whole new degree of freedom to manipulate of the electrons. 'Classical' transistors move/detect/switch charge, adding spin to the picture allows much more flexibility, and probably higher device speeds or data densities. Eg, perhaps microprocessors can go from binary as presence/lack of charge to spintronic up/down charge. Or perhaps even base-4 using presence/absence of both spin up and spin down flavors of electrons.
Re:Lots of research (Score:1)
I believe it was proven (sorry I don't have the source...) that the most efficient base to compute with is e, or 2.718... Since that has no physical interpretation at this time (how do you have a fraction of a state?), the next best number to use is 3 (trinary), simply because that is closer to 2.718 than 2 (binary).
Nanotechnology + Superconductivity?? (Score:0)
What would Nano-Superman be like? He's a tiny little bugger, but durn, is he strong!
IMPORTANT NEWS - Linux is dead!!! (Score:-1, Troll)
Fact: Linux has balkanized yet again. There are now no less than 120 separate, competing Linux distros, each of which has introduced fundamental incompatibilities with the other distros, and frequently with Unix standards. Average number of developers in each project (except for Redhat and Novell/Suse): fewer than five. Average number of users per project: there are no definitive numbers, but reports show that all projects are on the decline.
Fact: Trivial issues such as names and a lack of professionalism continue to plague Linux. At a recent Linux conference in San Francisco, a fight broke out between RMS (Richard M. Stallman) who says Linux should be called GNU/Linux and Linus Torvalds who created Linux and says that Linux should be called Linux. This led to a massive barroom style brawl involving at least 150 Linux geeks. The SFPD was called out to break up the melee, and arrested 150 people. It was estimated that at least 2 to 3 times that many were involved in the brawl, but there wasn't enough police on hand to arrest all of them. Thirty one people were hospitalized as a result of this brawl, and one person is still in a coma.
Fact: There are almost no Connectiva developers left, and its use, according to Netcraft, is down to a sadly crippled
Fact: X.org will not include support for Redhat's Fedora project. The newly formed group believes that Fedora has strayed too far from Unix standards and have become too difficult to support along with other Linux distros and Solaris x86. "It's too much trouble," said one anonymous developer. "If they want to make their own standards, let them doing the porting for us."
Fact: Ubuntu Linux, yet another offshoot of the beleaguered Debian "distro", is already collapsing under the weight of internal power struggles and in-fighting. "They haven't done a single decent release," notes Mark Baron, an industry watcher and columnist. "Their mailing lists read like an online version of a Jerry Springer episode, complete with food fights, swearing, name-calling, and chair-throwing. It also doesn't help that Ubuntu sounds like an obscure term for a gay orgy." Netcraft reports that Ubuntu Linux is run on exactly 0% of internet servers.
Fact: Debian Linux, which claims to focus on "being free" (whatever that is supposed to mean), is slow, and cannot take advantage of multiple CPUs. "That about drove the last nail in the coffin for Linux use here," said Michael Curry, CTO of Amazon.com. "We took our Debian boxes out to the backyard and shot them in the head. We're much happier running FreeBSD."
Fact: The Slackware Distro is now dead. The Slackware team could never get their distro to function on hardware other than Intel and S/390. Had they not been slacking off, Slackware would still be around.
Fact: Servers running SELinux, which claims to focus on security, are frequently compromised. According to Jim Markham, editor of the online security forum SecurityWatch, the few SELinux servers that exist on the internet have become a joke among the hacker community. "They make a game out of it," he says. "The SELinux team will scramble to make a new patch to fix one problem, and they've already compromised a bunch of boxes with a different exploit."
With these incontroverible facts staring (what's left of) the Linux community in the face, they can only draw one conclusion: Linux is already dead.
Alien Technology (Score:-1, Troll)
of thicknesses of order of few dozen nanometers? (Score:0)
I'm with the DJ... (Score:1)
Spin Doctor (Score:0)
boundless optimism (Score:1)
1) get an MS or PhD studying some exotic physical phenomenon
2) publish the results accompanied by wildly optimistic claims
3) ?
4) Profit!
Re:boundless optimism (Score:3, Insightful)
Re:boundless optimism (Score:2)
Now, University of Notre Dame physicist Boldizsar Janko and his colleagues believe they have found such a control technique. Their work, funded by the National Science Foundation through a Nanoscale Interdisciplinary Research Team grant, was published in the March 5, 2005, edition of the journal Nature.
I work in a biochemistry lab and if you can get a publication in one of the two most highly ranked journals Science or Nature, it helps you greatly in getting funding (as they have from NSF) or tenure.
Re:boundless optimism (Score:2)
Nice way to demonstrate your maturity. Makes me wonder if it's worth the time to bother replying to you.
Anyway, I did RTFA, and was responding to the parent's claim (or overextended southpark joke) that merely mentioning a bunch of trendy technobabble words in PhysOrg implies profit. That's why I specifically referred to "real" peer-reviewed journals.
Memory.... (Score:2)
.
-shpoffo
Re:Memory.... (Score:1)
Silicon-based magnets boost spintronics - 22 March 2004
http://www.newscientist.com/article.ns?id=dn4801 [newscientist.com]
Re:Memory.... (Score:2)
Is it too late? (Score:3, Insightful)
Is it too late to stop the proliferation of "-tron" words? "-tron" means nothing; "electrons" are so called because of the Greek word for amber, which the Greeks knew to be capable of producing a static charge. What if people abstracted part of that word out and started calling every new technology "something-ber"?
I think the technical name for the combining from "-tron" is a "cranberry morpheme," from "*cran," which apparently has no independent meaning.
Re:Is it too late? (Score:0)
Re:Is it too late? (Score:0)
Well, are we too cool for our shirt, or what?
Re:Is it too late? (Score:5, Informative)
Of course the buzzword 'spintronics' is is just 'electronics' with the word spin substituted in. The actual less-trendy synonym for spintronics is Magnetoelectronics, which is what it's usually referred to in the "real" science journals, not popular outlets like PhysOrg. magnetoelectronics.
BTW - since you mention Greek I thought a better example would be using the suffix Thon, as from Marathon, to refer to any excessivly long activity. Eg Bowl-a-thon, Dance-a-thon, Phone-a-thon, etc.
Re:Is it too late? (Score:1)
Re:Is it too late? (Score:0)
Re:Is it too late? (Score:2)
Does the "fruity and a little tart" bit explain why you prefer to remain "cranonymous"?
Re:Is it too late? (Score:0)
Re:Is it too late? (Score:1)
Is there a problem here? (Score:2)
Why? The -tron (or more accurately the -on suffix) words aren't Greek. They serve a useful purpose and the suffix is used in a single fairly well-defined way. I find it to be an ingenious solution to the labeling of particle-like objects.
How long before... (Score:1, Offtopic)
And what about cities down in Florida, like Lutz or Bithlo? Is there anyone down here who'd mind them being sent out into space?
Beat me to the punch. (Score:2)
OMGZ0RZ GOOGLE HAKT (Score:0)
http://www.myplanet.net/gthing/Picture%202.png [myplanet.net]
photonics or spintronics? (Score:2)
Re:photonics or spintronics? (Score:1)
In reality, I bet it will be a combination of the two. Photons have spin 1 and as others have pointed out and electrons are +-1/2 spin. I wonder if stimulating a photon out of an electron spin state change could be used as a direct interface between the two technologies?
Actually... (Score:2, Funny)
a quantum computer? (Score:2, Funny)
You 7ail it... (Score:-1, Troll)
Off topic, but odd. (Score:1)
Re:Off topic, but odd. (Score:0)
The opposite of old news... (Score:0)
Heh, heh... Only if! Slashdot: Speculation for nerds. Stuff that's not news yet. And this coming on the tails of "Firefox 1.1 - Nope, not yet." What happened? Everything used to be so old around here.
Boldizsar Janko (Score:0)
Its Old News (Score:1)
Re:Its Old News (Score:1)
Spintronics Holds Alot of Promise for Future (Score:1)
http://colossalstorage.net/ [colossalstorage.net]