Strong correlations versus Ucenter pairing and fractional AharonovBohm effect
Abstract
The influence of the interaction between electrons on the AharonovBohm effect is investigated in the framework of the Hubbard model. The repulsion between electrons associated with strong correlation is compared with the case of attraction such as Ucenter pairing. We apply the Betheansatz method and exact numerical diagonalization to the Hubbard Hamiltonian. It is shown that the quasihalfquantumflux periodicity occurs for any nonzero values of U for two electrons. For a large number of sites, or strong U, the quasiperiodicity becomes an exact halfquantum flux periodicity. The character of the state created on the ring is different in both cases. In Ucenter pairing the electrons are bound in pairs located on the same site. For strong correlations (large positive U) the electrons tend to be as far from each other as possible. We show by numerical solution of the Betheansatz equations that for three electrons the flux peiodicity of the groundstate energy is equal to 1/3. The onethird periodicity may occur even for small values of the ratio U/t, for the very dilute system. It is shown analytically using the Betheansatz equations for N electrons that for dilute systems with arbitrary value of the Hubbard repulsion U, the fractional AharonovBohm effect occurs with period f_{T}=1/N in units of the elementary flux quantum. Such a period occurs when the value Nt/LU is small, where L is the number of sites. Parity effects disappear in this fractional regime. We discuss possible experiments to detect fractional AharonovBohm effects.
 Publication:

Physical Review B
 Pub Date:
 June 1994
 DOI:
 10.1103/PhysRevB.49.16234
 arXiv:
 arXiv:condmat/9401064
 Bibcode:
 1994PhRvB..4916234K
 Keywords:

 71.27.+a;
 74.20.Mn;
 03.65.Bz;
 73.40.Gk;
 Strongly correlated electron systems;
 heavy fermions;
 Nonconventional mechanisms;
 Tunneling;
 Condensed Matter
 EPrint:
 30 pages (Latex), 10 figures upon request, submitted to Phys. Rev