Thursday, March 1, 2018

HW 7b

5. Calculate the characteristic speed associated with the massless Dirac fermions near the K point in graphene. That is, use the relationship, \(v_k = (1/\hbar)\) times the derivative of E vs k.
(hint: You can make this easier by doing it along the ky axis.)
a) What is the speed in the K to Gamma direction?
b) What is the speed in the K to M direction?
c) How does this speed compare to the speed of light?

Here is a possibly interesting article:
https://www.nature.com/articles/nature04233



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4 comments:

  1. Zack SchlesingerMarch 4, 2018 at 7:41 AM

    That is an interesting question. This course, physics 155, would hopefully gives you the tools to begin to go to a seminar on graphene and understand some things there. Quantum conductance is more advanced and something that may be covered in a grad class, like physics 232. It is not something we want to delve into here, but I think we are doing might provide some background that would be essential to later understanding that.

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  2. UnknownMarch 5, 2018 at 3:34 PM

    What E(k) function would we use for this?

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  3. Zack SchlesingerMarch 5, 2018 at 9:37 PM

    No need to overthink this question. The dispersion is linear near the K point, right? What is the slope? To what speed does that correspond? near the K point.

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