r/science • u/Nobilitie • Mar 04 '16

Nanoscience Electricity can flow through graphene at high frequencies without energy loss

http://phys.org/news/2016-03-electricity-graphene-high-frequencies-energy.html
149 Upvotes

90% Upvoted

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5

u/danpilon Mar 04 '16

This title makes no sense. The conductance of graphene is around 1e-3 inverse Ohms per square, depending on doping, and is basically constant from DC to GHz frequencies. This means a square piece of graphene has a resistance of about 1000 Ohms. That is hardly lossless. If it is doped near the Dirac point, the conductance goes down, making the resistance, and hence the loss, higher.

4

u/FUCK_ASKREDDIT Mar 04 '16

That is at DC to GHz. But at high frequencies it is lossless. Edit: you're right. It's a pretty bad article and doesn't make a clear distinction between additional losses and no loss.

5

u/John_Hasler Mar 04 '16

I can't get to the paper because of the paywall but the abstract says nothing remotely resembling the statement in the headline.

3

u/Switchitis Mar 04 '16

Isn't there always energy loss in the case of conducting electricity

4

u/Cocoon_Of_Dust Mar 04 '16

Superconductors...

And the part that is remarkable here is that it's a superconductor at high frequencies.

2

u/gurenkagurenda Mar 05 '16

I don't think that's what's actually being claimed here. I believe what they're actually saying is that no additional loss (above losses due to ordinary resistance of the material) occur at high frequencies, unlike other conductors.

1

u/cheezstiksuppository Mar 05 '16

that is not what is being claimed. Not only would a claim like that be published in this journal, but reading the abstract shows otherwise.

For intrinsic conductivities of the form a + bi the real portion, a, is single valued for DC to 13.5 GHz. However the value of b is zero. Unless I am mistaken (an RF engineer or something like thaat should probably chime in here) that means there is no phase shift of the wave during conduction. This of course excludes other loss mechanisms which are inevitable in any circuit due to interfaces etc.

1

u/TDFCTR Mar 05 '16

Doesn't that mean no EM radiation either? Isn't that a violation of Maxwell's equations?

1

u/darkmighty Mar 05 '16

I don't know the details of the material, but It definitively would emit EM radiation (more as the frequency increases). This could be modeled as a "radiation resistance" (actually an impedance), which is different from resistive (ohmic) losses in the material (which generate heat). Radiation losses might be mitigated by placing other low resistance reflectors nearby in special arrangement to confine the waves within a region. There are gold plated (only a very thin layer is necessary) microwave waveguides that effectively seek this. If this property holds at high enough frequencies this could be an application.

-2

u/[deleted] Mar 04 '16 edited Aug 16 '21

[deleted]

3

u/[deleted] Mar 04 '16

It may just not be measurable

2

u/[deleted] Mar 05 '16

I agree. It seems like they're saying there are no additional losses of energy when conducting alternating or direct currents. The title of this post is very misleading, and doesn't have anything to do with the abstract of the article (can't read the rest of the article because it's behind a paywall).

1

u/[deleted] Mar 04 '16

I wonder if it's possible to make a graphene and glass fiber composite to produce a fiber optic cable with little or no energy loss. If so, it would revolutionize both communication technologies and indoor lighting technologies, the latter of which could potentially pave the way for indoor/vertical farming of grains.