This is Eric's logbook for Nano Japan project from 2012.6.3-2012.7.27.

updated 2012.6.1 by Nugraha

Daily schedule

Goal of the project.

Schedule for discussion

Time and DayMonTueWedThuFri
09:00-10:00SatoNugrahaTapsanitTatsumiNugraha
13:30-14:30SaitoSimonHasdeoSimonTapsanit

Questions and Answers

Q: About Brillouin Zone

Hey guys! So I believe this is where I should post questions. I don't have any specific questions today, but was just trying to understand Brillouin zones and Bloch's theorem, which appear a lot in Saito-sensei's book on Carbon Nanotubes.

From google I have an ok idea of what Brillouin zones are, but am still trying to figure out how they relate to the energy gap of the cell such as on page 28 of the CN book. I was also wondering how on page 47 the Brillouin zone can be a long line segment instead of a polygon.

If anybody has any quick words of advice for how to understand Bloch's theorem that would be great as well! It's a little bit intimidating and I'm not sure if there's a simple way to begin to understand it.

Thanks so much and see you guys in a couple of weeks!

Eric

Answer (by Tapsanit)

Please consider my answers one by one in order to understand the Brillouin zone.

Q: About copy machine

Can I use a copy machine or printer?

A: (not solved)

Yes, and they are across the hall from my room.

Q: About library

I would like to know where the library is and how to use it.

A: (not solved)

The library is on the 7th floor. To check out a book I write information on a special wooden card and place it where the book had been. I also give the slip inside of the book to the librarian, and I return the book to the librarian.

Report

This part is basically written by Eric-san. Any other people can add this. Here the information should be from new to old so that we do not need to scroll.

Task from Tapsanit (Bloch's theorem and reciprocal lattice)

  1. Check that the &tex(): Error! The expression contains invalid characters.; satisfies the Bloch's theorem.
    • Answer: Bloch's theorem is: \[ T_{\vec a_i}\Psi = e^{(i\vec{k}\cdot\vec{a_i})}\Psi \] Here &tex(): Error! The expression contains invalid characters.; is a translation operator: &tex(): Error! The expression contains invalid characters.;. Then, also note that &tex(): Error! The expression contains invalid characters.; is a periodic function. We have &tex(): Error! The expression contains invalid characters.; because &tex(): Error! The expression contains invalid characters.; is a unit lattice vector. Thus: \[ T_{\vec{a}_i} \Psi(\vec{r}) = \Psi(\vec{r} + \vec{a}_i) \] \[ = e^{(i\vec{k} \cdot (\vec{r} + \vec{a}_i))} u(\vec{r} + \vec{a}_i) \] \[ = e^{i\vec{k} \cdot \vec{a}_i} [e^{i\vec{k}\cdot \vec{r}} u(\vec{r})] \] \[ =e^{i\vec{k} \cdot \vec{a}_i}\Psi\left(\vec{r}\light) \] The Bloch theorem is satisfied.
  2. Derive the unit vectors of reciprocal lattice, &tex(): Error! The expression contains invalid characters.; and &tex(): Error! The expression contains invalid characters.;, of graphene in Eq. (2.23) of CN book using &tex(): Error! The expression contains invalid characters.; and &tex(): Error! The expression contains invalid characters.; in Eq. (2.22).
    • Answer: Here we use \[ \vec{a}_i = {\rm unit~vector~of~real~lattice} \] \[ \vec{b}_i = {\rm unit~vector~of~reciprocal~lattice} \] \[ \vec{a}_i\cdot\vec{b}_i = 2\pi \] \[ \vec{a}_i\cdot\vec{b}_j = 0 \quad {\rm if} \quad i \neq j \] From Eq. (2.22) of CN book: \[
      \vec {a}_1 = \left(\frac{\sqrt{3}}{2}a,\frac{a}{2}\right), \quad
      \vec {a}_2 = \left(\frac{\sqrt{3}}{2}a,-\frac{a}{2}\right)
      \]

\[ \vec{a}_1\cdot\vec{b}_1 = a_{1x}b_{1x}+a_{1y}b_{1y}=b_{1x}\frac{a\sqrt{3}}{2}+b_{1y}\frac{a}{2}=2\pi \] \[ \vec{a}_2\cdot\vec{b}_1 = a_{2x}b_{1x}+a_{2y}b_{1x}=b_{1x}\frac{a\sqrt{3}}{2}-b_{1y}\frac{a}{2}=0 \]

\[b_{1y}\frac{a}{2}=b_{1x}\frac{a\sqrt{3}}{2} \] \[b_{1x}\frac{a\sqrt{3}}{2}+b_{1x}\frac{a\sqrt{3}}{2}=2\pi \]

\[b_{1x}=\frac{2\pi}{a\sqrt{3}} \] \[b_{1y}=\frac{2\pi}{a} \]

\[

\vec {b}_1 = \left(\frac{2\pi}{a\sqrt{3}},\frac{2\pi}{a}\right), \quad
\vec {b}_2 = \left(\frac{2\pi}{a\sqrt{3}},\frac{-2\pi}{a}\right)

\]

June 5 (Hasdeo teaches XX and YY. from 9:00-9:30) etc

Also, Florian-san showed me how to use the POV-Ray software. We installed it on the desktop machine and I worked through the basic tutorial.

Also, solve the diff eq for a Gaussian.

If I have time consider the infinite 1D series of spring mass problems, but in the case that all masses are the same, but the spring constants are different.

June 4

to do:


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