Author(s)

Mohammad Ali Vesaghi, Mohsen Babamoradi, Mehdi Heidari Saani

.

Many electron calculations on a simplest realistic two electron system i.e. H₂molecule was applied and as the consequence correlation effects was reflected accurately in the wavefunctions of H₂. Zanardi’s entanglement measurement, demonstrated that the maximum of entanglement for the ground state happens when U =J and this resolved the controversial conclusion of U = 0 for maximum entanglement. It was shown that the ground and third excited states are maximally entangled. These maximally entangled states and also the minimally entangled states are correlated to their spin’s property. The wavefunctions of the not magnetic (S = 0) ground and excited states explicitly depend on correlation parameters whereas the first excited states which is magnetic (S² = 2 and S_z≠0) is not entangled. The second excited state is not magnetic but its wavefunction does not depend on correlation parameters therefore it is a moderately entangled state. In any case, by switching on a magnetic field an entangled state with S_z = 0 can be extracted from a not entangled degenerate magnetic state. We suggest that in a realistic molecular scale system, there is two criteria for finding maximally entangled electronic states, first the system should be in moderately correlated regime and second the system should have a non-magnetic (S_z = 0) electronic state.

Hubbard Model, Entanglement, Hydrogen Molecule

M. Vesaghi, M. Babamoradi and M. Saani, "Maximally Entangled States in the Hydrogen Molecule: The Role of Spin and Correlation," Journal of Modern Physics, Vol. 2 No. 7, 2011, pp. 664-668. doi: 10.4236/jmp.2011.27079.