Current-controlled magnetism in T-shape tape-porphyrin molecular bridges

The electronic transport properties of T-shape tape-porphyrin molecular wires are studied by the self-consistent tight-binding formalism based on the density functional theory coupled with the Keldysh Green’s functions. Effects of the additionally fused single or double porphyrin macrocycles on the conductances are investigated. We predict the appearance of the current loop inside the molecules, which produces the local magnetic field whose strength is more than 0.1 T at the bias voltage of 1.2 V. Based on this finding, we propose a novel method for controlling the spin orientation of the cation site by the magnetic field generated by the current loop. This point is important also from the scientific viewpoints, since detecting a change in the spin orientation against inversion of the bias polarity should give a strong evidence of the quantum current loop inside the molecular wires. Furthermore, we consider the molecules where all the cations are substituted by some magnetic metal ions. In this case, if the current-induced magnetic field exceeds the effective coupling between the local magnetic moments, the T-shape tape-porphyrins are expected to work as uni-molecular memories.