Magnetically induced simultaneous slow and fast light

A Lambda-type atom coupled by a driving light field and an rf field is restudied. It shows that, owing to Autler-Townes splitting caused by the driving light field and the magnetic dipole transition caused by the rf field, the medium shows distinct characteristics and exhibits the simultaneous slow and fast light at two frequencies. This effect can be attained by simply increasing the magnetic field and making its Rabi frequency much stronger than the probe light. Also, slow and fast light can be converted flexibly between two frequencies by phase control of the rf field.