sir,
in the case of bilayer system with out applying any potential conduction band comes above zero and valance band come below zero.while applying positive voltage both valance band and conduction band come below zero.while applying negative voltage both valance band and conduction band come above zero.
but in my simulation both positive and negative voltage conduction band comes above zero and valance band come below zero.i didnt get valance band and conduction band shift.
with this i attached two band structure diagram.