  The switching behaviour of stilbene molecular system (SMS) device is
investigated with the help of non-equilibrium Green's function (NEGF) approach
using first principles calculation. The transmission spectrum of cis-isomers
confirmed that more electrons are transferred across the SMS-device using
optical excitation by the spin of C$=$C bond by torsion angle
$(\theta=180^\circ)$. The current-voltage characteristics show the lower
magnitude of current for trans-stilbene and higher magnitude of current for
cis-stilbene for an externally applied bias voltage. The outcome of the
proposed work suggests that cis and trans-stilbene molecular device can be used
as a switch.
