  Motivated by recent developments in measurements of electron spin resonances
of individual atoms and molecules with the scanning tunneling microscope
(ESR-STM), we study electron transport through an impurity under periodic
driving as a function of the transport parameters in a model junction. The
model consists of a single-orbital quantum impurity connected to two electrodes
via time-dependent hopping terms. The hopping terms are treated at the lowest
order in perturbation theory to recover a Lindblad-like quantum master equation
with electron transport.
  As in the experiment, the ESR-STM signal is given by the variation of the
long-time DC current with the driving frequency. The density-matrix coherences
play an important role in the evaluation of the ESR-STM signal. Electron
correlation is included in our impurity mode. The charging energy $U$ has
significant influence on the spin dynamics depending on the sign and magnitude
of the applied DC bias. Our model allows direct insight into the origin of the
ESR signal from the many-body dynamics of the impurity.

Mesoscale and Nanoscale Physics