title: Coupling artificial molecular spin states by photon-assisted tunnelling.
abstract: Artificial molecules containing just one or two electrons provide a powerful platform                 for studies of orbital and spin quantum dynamics in nanoscale devices. A well-known                 example of these dynamics is tunnelling of electrons between two coupled quantum                 dots triggered by microwave irradiation. So far, these tunnelling processes have                 been treated as electric-dipole-allowed spin-conserving events. Here we report that                 microwaves can also excite tunnelling transitions between states with different                 spin. We show that the dominant mechanism responsible for violation of spin                 conservation is the spin-orbit interaction. These transitions make it                 possible to perform detailed microwave spectroscopy of the molecular spin states of                 an artificial hydrogen molecule and open up the possibility of realizing full                 quantum control of a two-spin system through microwave excitation.
authors: Kavli Institute of Nanoscience, TU Delft, 2600 GA Delft, The Netherlands. lars.schreiber@physik.rwth-aachen.de
authors: L R
authors: LR
authors: Schreiber
authors: F R
authors: FR
authors: Braakman
authors: T
authors: T
authors: Meunier
authors: V
authors: V
authors: Calado
authors: J
authors: J
authors: Danon
authors: J M
authors: JM
authors: Taylor
authors: W
authors: W
authors: Wegscheider
authors: L M K
authors: LM
authors: Vandersypen