Friday, 24 August 2018

condensed matter - How to construct the matrix of Hamiltonians for a hexagonal lattice


For part of a project I need to solve the time-independent Schrödinger equation, $\mathbf H\Psi = E\Psi$ (where $\mathbf H$ is the matrix with elements $\langle\Psi_i|H|\Psi_j\rangle$, and $\mathbf S$ is a matrix with elements $\langle \Psi_i|\Psi_j\rangle$) for different lattices. I've done this for a square lattice but I'm having trouble with the hexagonal lattice. The difficulty I'm having with this is that the matrix is different depending on which sub lattice, A or B (see image below), you start on since they different possible directions (therefore different corresponding energies) to travel in.


Graphene Lattice


Edit: I forgot to mention that I am using the tight binding approximation so unless $\Psi_i$ and $\Psi_j$ are next to each other then $\langle\Psi_i|H|\Psi_j\rangle = 0$. In terms of the image above, only $\delta$ movement is allowed. $\delta_1$, $\delta_2$ and $\delta_3$ are all different in this case.


Anyone know how to make the matrix of Hamiltonians for this lattice? Any help would be greatly appreciated.




No comments:

Post a Comment

Understanding Stagnation point in pitot fluid

What is stagnation point in fluid mechanics. At the open end of the pitot tube the velocity of the fluid becomes zero.But that should result...