Molecular spintronics and topological properties of trans polyacetylene molecules
Mohammad Ali Mohammadi Keshtan
Iran University of Science and Technology
(January 3, 2024)
Exploiting the spin degree of freedom, in addition to the charge of electrons, is the goal of spintronics for accomplishing and optimizing the efficiency of solid state devices. Besides, investigation of the topological properties of matters has played a leading role during the last decades. Furthermore, organic materials and molecules are prospective candidates in these fields.
In this talk, we investigate the topological and spin dependent electron transport properties of the trans polyacetylene molecule on a two terminal nanoscale system by utilizing the Green’s function method in the framework of the Landauer-Büttiker formalism.
First, by using the Su-Schrieffer-Heeger Hamiltonian, effects of external electric and magnetic exchange fields are investigated. Though molecule Hamiltonians do not respect the chiral symmetry, molecules with the intracell single carbon-carbon bonding and an even number of monomers in their chains have two edge states and possess topological properties. A perpendicular exchange magnetic field induces the spin polarization in different electron energy regions, which are expanded by stronger exchange fields. This spin polarization can be manipulated by applying the perpendicular electric field and remains robust against the transverse electric field variations.
Next, a new tight-binding Hamiltonian up to the third nearest neighbours for the dimerized trans polyacetylene molecule is proposed by using the linear combination of atomic orbitals in the Slater–Koster approach in combination with the density functional theory band structure data. The effects of strain are also considered in the Hamiltonian. At a peculiar value of compression strain, the electron conductance shifts 0.27 eV in energy, which is an exploitable magnitude for straintronic applications.
Therefore, this proposed device works as a perfect spin filter, spin memory, strain sensors and strain switches.