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Rosa edited section_Density_of_states_In__.tex
over 8 years ago
Commit id: c52db486a9bce7ae8f5c5d515916a8c03dda8846
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|\sin k(N+1)-\sin kN e^{iq}}|^2 = \sin^2 k(N+1)+\sin k N^2 -2\cos q \sin kN\sin K(N+1)
\end{equation}
with 2\cos q =2\cos k-(V_g/t), then
\begin{multline}
\sin^2 k(N+1)+\sin k N^2 -2\cos q \sin kN\sin K(N+1)
&=& \sin^2 k(N+1)+\sin k N^2 -\cos k \sin kN\sin K(N+1) +\frac{V_g}{t} \sin kN\sin K(N+1)
\end{multline}
Now we simplify the following term
\begin{equation}
\sin^2 k(N+1)+\sin k N^2 -2\cos
q \sin kN\sin K(N+1) = \sin^2 k(N+1)+\sin k N^2 -2\cos k \sin kN\sin K(N+1)
+\frac{V_g}{t} =\sin k(N+1) \left[ \sin
kN\sin K(N+1) k(N+1)-2 \cos k \sin kN \right]+\sin k N^2
\end{equation}
Now then we
simplify split the
following 2\cos k in two contributions (we do not consider the last term
$\sin k N^2$ for these simplifications)
\begin{equation}
\sin^2 k(N+1)+\sin \sin k(N+1) \left[ \sin k(N+1)- \cos k \sin kN \right] =\sin k(N+1) \left[ \sin kN \cos k
N^2 -2\cos +\cos kN \sin k- \cos k \sin
kN\sin K(N+1) kN \right]
\end{equation}
Then we have
\begin{multline}
\sin k(N+1) \left[ \sin kN \cos k +\cos kN \sin k- \cos k \sin kN \right] -\sin k(N+1) \sin kN \cos k
\\
=\sin k(N+1) (\cos kN \sin k- \cos k \sin kN )
\end{multline}
However we need to add the term $\sin k N^2$ to simplify the whole denominator, then
\begin{multline}
\sin^2 k(N+1)+\sin k N^2 -\cos k \sin kN\sin K(N+1) =\sin k(N+1) (\cos kN \sin k- \cos k \sin kN ) + \sin k N^2 =
\\
\sin k(N+1) \cos kN \sin k + \sin k N (\sin kN-\cos k\sin k(N+1))
\end{mutline}
Using the fact that $\sin k(N+1)=\sin kN \cos k +\cos kN \sin k$, then the whole expression is simplified to
\begin{multline}
\sin k(N+1) \cos kN \sin k + \sin k N (\sin kN-\cos k\sin k(N+1)) = \sin^ k
\end{mutline}
Therefore the final result reads
\begin{equation}
|c_1|^2 = D^2\frac{\sin^2 q \sin ^2 k}{\sin^k -\frac{V_g}{t}\sin kN \sin k(N+1)}
\end{equation}
Finally the density of states coincides with the one in \cite{Park_2013}. Using the fact that we are using $k$ and $q$ wavevectors in units of $a$, the lattice spacing, we have
\begin{equation}
\rho(E)=\frac{\sin q a\sin^ka}{(\pi a t)(\left\sin^2(ka)+\frac{eV_g}{t}\sin{k(N+1)a}\right)\sin kNa}
\end{equation}
...