Many-body theory of current-induced fluorescence in molecular junctions

Nonequilibrium superoperator Green's function theory is used to calculate the fluorescence signal of molecules induced by currents in scanning tunneling microscope junctions. The spectrum of benzene and its variation with tip position and bias are simulated at the density functional theory level. The formal analogy with laser-induced fluorescence is pointed out. Many-body effects can be accounted for through self-energies and the Keldysh Dyson equations. The sum-over-orbital expressions obtained within density functional theory may not be expressed as an amplitude square. This is due to dephasing effects induced by the many-electron excitations, which act as a bath.