10.23.2008

Client/Matter/State of Matter

There may be a new state of matter. Electrons, which normally travel around the nucleus of an atom on a 2D plane (a disk, or an orbit), were seen to shift to a "quasi 3D plane" when subjected to massive magnetic forces at near 0 Kelvin.

Practical uses: use the shift in state of a matter to store bits of data, allowing bits to shrink to the single particle level. Well, perhaps "practical" isn't the perfect term.

2 comments:

David said...

Isn't this describing the phenomenon which used to be called "superconductivity"?

Maxim said...

Oh goody goody goody! I finally get to comment here about something other than politics! AND I get to be a physics-science-snob-knowitall in the process. My day has been made. :)

You might have noted that some of the commenters at the Gizmodo post (esp. see DisposableInterloper) picked up on the fact that they did a bad job of relaying an already poorly-written press release. Which happens a lot when new scientific findings are presented to "the public" in an effort to make them understandable (c.f. climate change and everything surrounding it ... but I digress).

First, a basic comment about the "2-D" vs "3-D" electrons phenomenon. The "disk" or "orbit" picture of electrons around an atom is a simplified model. More accurately, electrons orbit an atom within spherical "shells" (at least some do -- others have much weirder orbital shapes, see this image for the odd shapes). Anyway, none of the electrons are at all confined to a 2-D orbit/disk around an atom. So let's put that whole picture aside for now -- that's not what this is about anyway.

Instead, after looking at the published paper itself (most of which is way out of my league), here's my best explanation of what's going on here:

They have a very thin layer of semiconductor (not important exactly what it is, let's just call it GaAs), in which they look at what the "free" electrons are doing -- i.e. ones not associated with any particular atoms, which wander around in the GaAs layer. [Such electrons, for instance, enable current to flow in normal metals/conductors (and semiconductors, under specific conditions)]. In this particular situation, because the GaAs layer is so thin, the electrons are "stuck" in it and prevented from moving perpendicular to the layer, so for them, effectively, the 3rd dimension doesn't exist. That's what they mean when they say "2-D electron gas."

Now, they're looking at what happens when they apply some crazy-strength magnetic fields to this layer of material. Normally (low mag. field) these electrons conduct pretty well -- i.e. they wander around in the material pretty freely. But with the insanely high-strength magnetic field, they "snap" into this weird configuration they haven't seen before, which they call "quasi-3D" -- probably because it's not really 3D, but not 2D either, and they have no better name. In this configuration, the conductivity gets very poor, because the electrons can no longer wander about freely. Apparently, this behavior wasn't expected.

Now - why is this notable? It's not, really. These guys did a good job of marketing themselves by linking this behavior to a transistor -- i.e. a material which can be switched from a conductive to a non-conductive state. Once you get someone to call your thingy a "transistor," the next logical thing to say is Moore's law! after which everyone discussing it is contractually obligated to state that it could "break" the physical limits of Moore's law. Well, this thing can, but at 35 milliKelvin, and with 10+ Tesla magnetic fields (the Earth's mag. field is on the order of 0.00005 Tesla on the surface).

BUT, even though the discovery is not at all "useful," it is still Very Sexy Physics. Especially because it was unexpected, so it'll give the theorists a bunch to scratch their heads about. As such, it helps us take another infinitesimal and tiny step toward understanding the fundamental physics of the universe (or, as some might call it, Knowing G-d).

A final note in response to david -- this is not superconductivity at all. It's sort of the opposite, since the relevant effect is reduced conductivity in the material, rather than nearly-infinite.

Whew. That was some hardcore geeking-out. This concludes your Five-Minutes-of-Nerd. I hope you enjoyed it.

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