33 research outputs found
T>0 properties of the infinitely repulsive Hubbard model for arbitrary number of holes
Based on representations of the symmetric group , explicit and exact
Schr\"odinger equation is derived for Hubbard model in any
dimensions with arbitrary number of holes, which clearly shows that during the
movement of holes the spin background of electrons plays an important role.
Starting from it, at T=0 we have analyzed the behaviour of the system depending
on the dimensionality and number of holes. Based on the presented formalism
thermodynamic quantities have also been expressed using a loop summation
technique in which the partition function is given in terms of characters of
. In case of the studied finite systems, the loop summation have been
taken into account exactly up to the 14-th order in reciprocal temperature and
the results were corrected in higher order based on Monte Carlo simulations.
The obtained results suggest that the presented formalism increase the
efficiency of the Monte Carlo simulations as well, because the spin part
contribution of the background is automatically taken into account by the
characters of .Comment: 26 pages, 1 embedded ps figure; Phil. Mag. B (in press
Field and chirality effects on electrochemical charge transfer rates: Spin dependent electrochemistry
This work examines whether electrochemical redox reactions are sensitive to the electron spin orientation by examining the effects of magnetic field and molecular chirality on the charge transfer process. The working electrode is either a ferromagnetic nickel film or a nickel film that is coated with an ultrathin (5\u201330 nm) gold overlayer. The electrode is coated with a self-assembled monolayer that immobilizes a redox couple containing chiral molecular units, either the redox active dye toluidine blue O with a chiral cysteine linking unit or cytochrome c. By varying the direction of magnetization of the nickel, toward or away from the adsorbed layer, we demonstrate that the electrochemical current depends on the orientation of the electrons\u2019 spin. In the case of cytochrome c, the spin selectivity of the reduction is extremely high, namely, the reduction occurs mainly with electrons having their spin-aligned antiparallel to their velocity