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QuantumATK => General Questions and Answers => Topic started by: pengdou on December 13, 2010, 10:21

Title: one questions about the Graphene Nanoribbon Tutorial
Post by: pengdou on December 13, 2010, 10:21

Dear developers,

     In   Tutorial of Graphene Nanoribbon on this website "http://quantumwise.com/documents/tutorials/BasicGrapheneTutorial/XHTML/chap.zigzag_transport.html#chap.zigzag_transport.perfect_transmission", it said the enhanced transmission around the Fermi level was due to a peculiarity in the band structure of the zigzag ribbon. In my opinion, in such a one dimensional transport system, the electron would be transfered from the source electrode to the drain electrode only through the gamma(0,0,kz=0) point in the Brillouin zone and thus the peculiarity in the band structure of the zigzag ribbon far away from the gamma(0,0,kz=0) point along the kz line should be no use for electron transport and couldn't be related with the enhanced transmission around the Fermi level. But my opinion should be wrong. Do the kz points other than gamma(0,0,kz=0) point  also take part in the transport progress in such one  dimensional transport system?
   Thanks in advance!!!

Title: Re: one questions about the Graphene Nanoribbon Tutorial
Post by: zh on December 13, 2010, 18:18

Regarding to the k, it also stands for the kinetic momentum of electrons. Sure, the electron states with kz[tex]\neq[/tex] 0 also have contribution to the electron transport.

Title: Re: one questions about the Graphene Nanoribbon Tutorial
Post by: pengdou on December 14, 2010, 12:47

Quote from: zh on December 13, 2010, 18:18

Regarding to the k, it also stands for the kinetic momentum of electrons. Sure, the electron states with kz[tex]\neq[/tex] 0 also have contribution to the electron transport.

Dear zh,
   Thanks for your answer. But I am still confused about the k point. For example,as Nordland mentioned in "http://quantumwise.com/forum/index.php?topic=36.0",for a 1D system the 'Quantum Numbers' should be set as  [0.0, 0.0, 0.0]. Thus  in the transmisson spectrum, all "Transmission Eigenvalues" at different energies only tunnel through gamma point [0.0, 0.0, 0.0]. I still don't know through which k-point the electrons with kz[tex]\neq[/tex] 0  tunnel? Do they also tunnel through gamma point [0.0, 0.0, 0.0] during the transport progress?

Title: Re: one questions about the Graphene Nanoribbon Tutorial
Post by: kstokbro on December 14, 2010, 13:10

For the transmission calculation you only specify k-points in the x and y directions,
The k-points in the transport direction are selected through the energy, i.e. T(E0, kx,ky) gives the transmission of all
states with energy, E(kx,ky,kz) = E0

Title: Re: one questions about the Graphene Nanoribbon Tutorial
Post by: pengdou on December 17, 2010, 08:27

Quote from: kstokbro on December 14, 2010, 13:10

For the transmission calculation you only specify k-points in the x and y directions,
The k-points in the transport direction are selected through the energy, i.e. T(E0, kx,ky) gives the transmission of all
states with energy, E(kx,ky,kz) = E0

Thanks very much for your and zh's every valuable word.  I get your point a little bit after several days' thinking over them.