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Researchers Put 'Spin' in Silicon

Posted by CowboyNeal on from the while-the-dj-revolves-it dept.

ccellist writes "Physorg.com is reporting on the University of Delaware and Cambridge NanoTech's experiments regarding 'spintronics,' or the ability to use information about electron spin in atoms of silicon to encode information, much like we use information about an electron's charge state in computers today. 'Spintronics' research hopes to usher in a new age of computer speed and performance by measuring and even controlling the angular momentum displayed by all electrons, and using this information to encode data. Researchers for the first time have successfully conducted the spin of electrons in a custom-made silicon chip, a process known as 'spin transport.'"

8 of 50 comments (clear)

  1. Angular momentum by suv4x4 · · Score: 4, Funny

    Quoting from a movie I saw once. The editor tells the article author how he edited his work:

    Editor: "I replaced atom with molecule here and there, atom repeats too much"
    Author: "But... it's not the same thing at all!"
    Editor: "Oh come on! Who'll know the difference. Molecule, atom.. same thing to me."

    So, in the light of this, particle "spin" isn't about an electron actually spinning, and thus "angular momentum" as seen in the article text, so that's pretty hilarious replacement.

    Another thing you may want to know for future articles: quark colors also aren't actual colors.

    1. Re:Angular momentum by digitalderbs · · Score: 4, Informative

      nah, it's all appropriate. The angular momentum is on the magnetic moment produced at the electron from an applied magnetic field, due mainly to the Zeeman interaction. The spin itself is the magnetic moment of the electron. Changes in the magnetic field (non parallel) apply a torque on the moment and change its orientation. The motions are described by the quantum angular momentum equations .. i.e. commutation relations. These commutation relations are the quantum analog to the classical angular momentum equations.

    2. Re:Angular momentum by chrisb33 · · Score: 3, Informative

      Unfortunately, the "hilarious" joke is on you, since spin actually does refer to angular momentum. It can even be interchanged with "orbital" (extrinsic) angular momentum while obeying momentum conservation, and (as the article mentions) can be measured using a magnetic field.

      A quick look at wikipedia before posting is usually helpful.

  2. It's actually quite straightforward. by Anonymous Coward · · Score: 3, Informative

    This sort of physics is actually pretty easy to comprehend, so I'm not sure how it could be twisted.

    Basically, we can think of an atom as a sea urchin. So around this atom, we have a number of spikes. These can be considered the electrons of the atom. Now, this is a major simplification of Schroedinger's equation, but essentially each spike represents the probabilty of locating an electron within a volume of space.

    Now, these spikes come in pairs, in order to balance each other. They're on opposite sides of the sea urchin atom. They slide around the atom, but they're always opposite to one another. This is typically called the Pauli exclusion principle by physicists.

    So to an external viewer looking at the atom, it appears as though the spike pairs are spinning around the circumference of the atom. Relative to the viewer's position, these spike pairs are moving either clockwise or counterclockwise around the atom. This is how we get the two different spins, which thus can be used to repesent binary information.

    Now, when you're dealing with larger atoms, with many electron pairs, the interaction between the electrons leads to a greater degree of electron stability and predictability. Thus electron pairs will still spin around the atom, but they'll travel in a path that's actually quite consistent, relative to the other electron pairs. By focusing only on certain electron pair paths, and the direction that they spin around the atom relative to the viewer's position, we can store large amounts of binary data per atom.

    1. Re:It's actually quite straightforward. by Anonymous Coward · · Score: 3, Insightful

      You're actually thinking of the outdated Rutherford-Moore model of the atom. While it was practical back in its day, it doesn't adequately describe much of the observed phenomena since that time. That's why we need to look towards models like those of quantum mechanics, where we're not dealing with randomness (because we're not in actuality), and instead we're dealing with probability distributions.

      Think of the sea urchin spikes as the probability density function of a three-dimensional Bell curve. We have a greater probability of finding an electron closer to the atom thus resulting in the greater spread at the bottom of the spike. On the other hand, we have a small probability of finding an electron the further away we go from the atom, represented by the smaller spread (ie. the point) of the spike.

  3. Expanding markets by HotBBQ · · Score: 3, Funny

    I have a far more entertaining idea for spinning silicone. It mostly involves cheesy stage names and tassels.

  4. Sounds like MRI by necro81 · · Score: 3, Interesting

    After spin injection, electrons in the silicon were then subjected to a magnetic field, which caused their spin direction to "precess" or gyrate (much like gravity's effect on a rotating gyroscope), producing tell-tale oscillations in their measurement.

    This sounds like the process used in Magnetic Resonance Imaging. In MRI, they use a BIG magnet to create a very strong magnetic field in a person's body. The main field is usually 1-3 Tesla, depending on the scanner (for reference, Earth's magnetic field is 30-50 microtesla). Then they use smaller magnets to establish a gradient in that main field, and RF pulses to query the spin precession of atoms in the body. In the case of human imaging, I think they focus on the spin precession of a hydrogen nucleus (a proton) in water. In function MRI, they focus on hemoglobin (which contains a little ferromagnetic iron, ya see), to determine where blood is most present. See this for an exhaustive overview of how it works.

    Their spintronics methods sound similar, except it's focused on a much smaller volume (a chip instead of a human body), and are tuned to the electrons in doped silicon. Very cool.
  5. Re:Big mistake in the summary by l2718 · · Score: 3, Informative

    Obviously the charge of an electron is constant (in case you get confused eV is a measurement of velocity, not charge). What we use in computers today is the QUANTITY of electrons "flowing" (these days tunnelling may be a better term) through non-conductive layers.

    Man, there are so many errors here I don't know where to begin. The Electron-Volt (eV) is a unit of energy (the work required to move an electron across a potential different of one Volt). Digital computers do not depend on the magnitude of the current, but on its abssence or presence. In fact, the goal is to have as little current as possible (less losses due to heat and radiation) -- we are nearing single-electron transistors. "Spintronics" would instead carry the information in the spin state (up or down) of an electron. The reference to "charge" probably stems from memory, where information is stored in the magnetization state of a small amount of matter.