Coherent population trapping in two electron three-level systems with aligned spins

This work investigates the possibility of realizing coherent population trapping (CPT) in a two-electron three-level system with parallel spins. Making an analogy with solid-state physics, this study demonstrates that a V-type three-level system with two electrons can be described as a Λ-type three-level system for one single hole. Cancellation of the probe field absorption is obtained when the hole is placed in the dark state. Alternatively, in terms of the two-electron V-type system, the CPT condition is realized when one electron is placed in the ground state and the other one in the bright combination of the excited states. In addition, when the electron-electron Coulomb repulsion is taken into account, it is shown that this technique offers the possibility of measuring, with subnatural resolution, some superposition-state matrix elements of the electron-electron correlation that due to their time dependent nature are inaccessible by standard measuring procedures.