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New Technology For Converting a Metal To a Semiconductor With a Laser
rtoz writes "Researchers at MIT have succeeded in producing and measuring a coupling of photons and electrons on the surface of an unusual type of material called a topological insulator. This type of coupling had been predicted by theorists, but never observed. The researchers suggest that this finding could lead to the creation of materials whose electronic properties could be 'tuned' in real time simply by shining precise laser beams at them. This work opens up a new avenue for optical manipulation of quantum states of matter. Their findings suggest that it's possible to alter the electronic properties of a material — for example, changing it from a conductor to a semiconductor — just by changing the laser beam's polarization. For example, a property called a bandgap — a crucial characteristic for materials used in computer chips and solar cells — can be altered by shining a polarized laser beam at the material."
So... you're saying that the whole "we've got to alter the polarity on the deflector array" technobabble on Star Trek, may be retconned... as reality? With lasers, onto metals?
Daaaayyym.
Seriously though - neat new twist on material science, and great exploration of particle coupling/entanglement! Could result in some rather odd, but promising advances in chip design and layout.
Ryan Fenton
Does the material exhibit these properties while the laser is hitting it, or is it affected permanently?
We've known about this since the turn of the last century. It's the photoelectric effect. Every material has a wavelength where if it is struck by a charged particle at or above that, it will absorb it and then emit an electron. This isn't news.
What's news is that we've now reached a sufficient level of understanding regarding the engineering of electro-optical systems that we are starting to build devices where the primary logic is based on optics, not electronics. This is an advancement of technology, not of understanding.
I am a bit confused by what you said. An incident photon at wavelength (Lamda) or smaller will eject an electron ( photo electric) and thermal excitation of a material like the cathode of a tube will also eject electrons. I am not getting where the charged particle comes in. From TFA:
In other situations, light can modify a material’s behavior — but only when it’s absorbed, transferring its energy to the material. In this experiment, Gedik says, the light’s energy is below the absorption threshold. This is exciting, he says, because it opens up the possibility of switching a material’s behavior back and forth without inducing other effects, such as heating — which would happen if the light were absorbed.
What they are talking about is changing the bandgap with the incident angle of polarized infrared laser light.
That's girlintraining's schtick. He comes in, makes some kind of pseudo-intellectual post full of wrongness, and the uneducated slobs mod him up. It really shows how uninformed the average slashdotter is.
no, this is not the photoelectric effect. the "bandgap" is range of energy levels where no electron exists. Thisproperty separates insulators, semiconductors and conductors. They are altering the bandgap with polarization of light
The article mentions that one can change the bandgap of a material with the laser. Isn't this what has been holding back graphene semiconductors--that they have a zero bandgap? Could this technique be used to produce practical graphene semiconductors?
Like a good neighbor, fsck is there
Jesus Christ you people have an obsession with 3D printing, combined with a hilarious naivete about what it actually does.
You might be surprised to learn there are a wide variety of effects and principles involving the interaction two words you put in bold, photons and electrons, that have nothing to do with the photoelectric effect. This has to do with altering the electronic structure, not ejecting electrons, or just giving them energy less than excitation. The creation and tuning of a bandgap when there was no before, creating a region in an energy diagram where electrons can't get to by use of light is something rather different. Might as well conflate the principle of buoyancy with the operation of something like an adsorption pump, after all they both involve movement of fluids, never mind one involves vertical forces against gravity and another has to do with confining something to a surface.
OMG, you know just enough Physics to be dangerous.
Photoelectric effect has NOTHING to do with the bandgap of materials. The former only concerns the energy difference between a bound electron (bound in the material as a whole, or bound to an atom, doesn't matter) and the free electron states. The latter comes entirely from the aggregated properties of the material, usually in the form of a crystal structure.
You can have photoelectric effect on free atoms or molecules, e.g. on a gas. There is no bandgap in a gas (there isn't even bands to begin with).
Being able to alter the bandgap means changing the energy levels within a crystal, which has a meaning even if those bands are all empty (i.e. no electrons in the bands), nor does it absolutely requires absorption or emission of photons (even though it may).
In comparison, there is no meaning to photoelectric effect without any electrons, or without photon absorption.
The article is very light on details. I wonder if that could make it possible to produce small series of microchips. It would be an incredible tool for your local fablab...
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
And anybody who points it out gets modded down to 0. Sigh.
Go to Heaven for the climate, Hell for the company -- Mark Twain
No, you are confused. The photoelectric effect ejects an election. Altering bandgap can be done without ejecting electron.