How does the ATK software apply a bias voltage on the homogeneous devices

[zhaopeng77]

Dear Sir,
 
     In many graphene nanoribbon devices, the left electrode, right electrode and the center of the device appear to be homogeneous. In light of this, a bias voltage is unlikely to be applied to the central region. However, the ATK software seems managed to do so. Could you comment on this and explain it in details. In particularly, how does the ATK software apply a bias voltage on the devices and where does the primary potential drop locate?
    Long for your reply. And thanks in advance.

Best Wishes,

[Jess Wellendorff]

Perhaps the spin-up HOMO is unlikely to be populated?

[Jess Wellendorff]

Where does the spin-down electron "go" in order to facilitate transmission? Perhaps the spin-up HOMO electron have nowhere to "go"?