Correlated disordered electrons and organic magnetoconductance

Abstract

The purpose of this paper is to explore the magnetoconductance (MC) effect in an organic semiconductor. By taking into account the external magnetic field and the hyperfine interaction, we determine the magnetoconductance (MC) from a numerical solution by using a steady-state rate equation for correlated electrons in Gaussian disordered systems. The ingredient of this model is that at thermal equilibrium, the spins of the polarons relax in the same direction as the local magnetic fields. We have investigated the MC dependence of the external magnetic field, the hyperfine interaction, the carrier densities, the intra-site coulomb energy, and the applied electrical field. We show that the interplay between the Hubbard energy and the charge-carrier density leads to positive and negative magnetoconductance. The theoretical calculations are in qualitative agreement with the experimental results.

Magnetoresistance in organic semiconductors: Including pair correlations in the kinetic equations for hopping transport

“…The averaging is performed over all right-hand side of the equations, therefore pair correlations contribute to the currents described by Eqs. (20,21). The electron transition rates W ij acquired additional upper indexes in (21) corresponding to the roles of sites i and j.…”

“…The effect was demonstrated with the Monte-Carlo simulations. This study was followed by several attempts to include these parallel/antiparallel configurations into the conventional theory of hopping conduction [14][15][16][17][18][19][20]. The number of these attempts itself indicate the interest in generalizing the conventional theory of hopping transport to include the effects similar to OMAR.…”

Microscopic theory of organic magnetoresistance based on kinetic equations for quantum spin correlations

“…Note that the same coefficients Φ qq ′ p enter the equations (20) and (24). The second term in r.h.s.…”

“…In a stationary system the derivatives dc P I /dt are equal to zero. Therefore the equations (9), (19), (20), (24) and (25) compose a closed system of linear equations for the correlations potentials. It incudes all the charge and spin correlations.…”

Electric current noise in mesoscopic organic semiconductors induced by nuclear spin fluctuations

“…In this paper we suggest to measure the current noise spectra in mesoscopic organic semiconductors. Although the nuclear spins are often assumed to be static [12,17,[24][25][26], their dynamics unavoidably takes place due to the interaction with the electrons. This dynamics is slow and does not change the average electric current.…”