  We apply a first-principles computational approach to study a light-sensitive
molecular switch. The molecule that comprises the switch can convert between a
trans and a cis configuration upon photo-excitation. We find that the
conductance of the two isomers vary dramatically, which suggests that this
system has potential application as a molecular device. A detailed analysis of
the band structure of the metal leads and the local density of states of the
system reveals the mechanism of the switch.
