Biomedical subjects

A A Aligia

Publications and source records attributed to A A Aligia.

4 recordsLinked to original sources

PubMed2006

Effective Kondo model for a trimer on a metallic surface.

I consider a Hubbard-Anderson model which describes localized orbitals in three different atoms hybridized both among themselves and with a continuum of extended states. Using a generalized Schrieffer-Wolf transformation, I derive an effective Kondo model for the interaction between the doublet ground state of the isolated trimer and the extended states. For an isoceles trimer with distances a, l, l between the atoms, the Kondo temperature is very small for l a when a is small. The results agree with experiments for a Cr trimer on Au(111).

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PubMed2004

Detection of topological transitions by transport through molecules and nanodevices.

We analyze the phase transitions of an interacting electronic system weakly coupled to free-electron leads by considering its zero-bias conductance. This is expressed in terms of two effective impurity models for the cases with and without spin degeneracy. Using the half-filled ionic Hubbard ring, we demonstrate that the weight of the first conductance peak as a function of external flux or of the difference in gate voltages between even and odd sites allows one to identify the topological charge transition between a correlated insulator and a band insulator.

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PubMed2004

Spin-charge separation in Aharonov-Bohm rings of interacting electrons.

We investigate the properties of strongly correlated electronic models on a flux-threaded ring connected to semi-infinite free-electron leads. The interference pattern of such an Aharonov-Bohm ring shows sharp dips at certain flux values, determined by the filling, which are a consequence of spin-charge separation in a nanoscopic system.

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PubMed2004

Exact bond ordered ground state for the transition between the band and the Mott insulator.

We derive an effective Hamiltonian H(eff) for an ionic Hubbard chain, valid for t< >t) and the Mott insulator (MI) (U-Delta>>t). Using spin-particle transformations [Phys. Rev. Lett. 86, 1082 (2001)]], we map H(eff)(U=Delta) into an SU(3) antiferromagnetic Heisenberg model whose exact ground state is known. In this way, we show rigorously that a spontaneously dimerized insulating ferroelectric phase appears in the transition region between the BI and the MI.

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