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nnp:transmission:transmission_through_a_3d_nanowire

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nnp:transmission:transmission_through_a_3d_nanowire [2019/10/21 10:54]
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-===== Transmission through a 3D nanowire ===== 
-We apply the Contact Block Reduction (CBR) method to a simple GaAs nanowire of cuboidal shape. 
-The corresponding tutorial for nextnano<​sup>​3</​sup>​ is [[https://​www.nextnano.com/​nextnano3/​tutorial/​3Dtutorial_CBR_nanowire.htm|here]]. ​ 
  
-==== System ==== 
-We consider a GaAs cuboidal tube of dimensions 10 nm$\times$10 nm$\times$20 nm. Two leads of 10 nm$\times$10 nm each are attached to the edge of the device. 
- 
-==== Input file ==== 
-To simulate 3D (or 2D) system with CBR method in nextnano++ correctly, The quantum regions have to be appropriately specified in the input file.  
-<​code>​ 
-quantum{ 
- region{ 
- name = "​lead_1"​ 
- x    = [-6,6] 
- y    = [-6,6] 
- z    = [-0.1,0.1] 
- boundary{ x=dirichlet y=dirichlet z=cbr } 
-                Gamma{ num_ev = $num_eigenstates_device } 
- } 
-} 
-</​code>​ 
-The perpendicular directions, i.e. x- and y-directions,​ of the system are elongated by one grid due to the treatment of edge points in nextano++. Since the simulation is three dimensional,​ the lead region specified here has to be two dimensional. The number $\pm0.1$ is chosen to be smaller than the grid spacing, so that the region "​lead_1"​ becomes a 2D sheet (//Note: this is slightly different in nextnano<​sup>​3</​sup>​ input//). CBR boundary condition has to be imposed in the propagation direction, i.e. z-direction,​ whereas Dirichlet boundary condition is set for perpendicular directions. 
- 
-<​code>​ 
-cbr{ 
-         name = "​device"​ 
-         lead{ name = "​lead_1"​ } 
-         lead{ name = "​lead_2"​ } 
-         ​delta_energy ​  = $delta_energy 
-         ​abs_min_energy = $E_min 
-         ​abs_max_energy = $E_max 
-         ​options ​       = [1, 0, 0] 
-} 
-</​code>​ 
-Here we specify the device region and leads attached to the device. The program calculates transmission through the region "​device",​ from "​lead_1"​ to "​lead_2"​. The resolution, minimum and maximum of the energy axis can be also tuned here.