Ring Polyacetylene Molecules Bridge Conductance

With the rapid improvement of the integrated level of computers, the sizes of devices are reduced, and the quantum effects become obvious, all of which offer a very good opportunity for the development of devices. Therefore, the study of molecular devices becomes a multi-disciplinary hot spot relating to physics, chemistry, material science, and so on.In this paper, we will choose a polyacetylene loop as a molecular bridge, based on Landauer-Buttiker transport theory and tight-binding approximation, we take a detail investigation on the electronic transmission properties of this molecular bridge connected with multi-terminal metals by solving the scattering wave function for the system, obtain some important conclusions, which are valuable in designing molecular devices.First, in the two-terminal connection model, we find that when the coupling between leads and the polyacetylene loop is very weak, there is a strong oscillation of conductance changes with energy, as the coupling becomes strong, the oscillation tends to weak; When the loop becomes large, the number of the tunneling peak will increase; The energy of conductance peaks and local density peaks are nearly same, and the figures of conductance and local density changes with energy are similar, thus the conductance and local density are correlated, and so on, and we give the analysis and explanation individually. Then, we give the probability amplitude of each lattice point in the loop, compare the probability amplitude of output sites with other ones. We then find the values of conductance peaks are different if the lead sites are changed, so it can be used to design molecular devices.Then, we study the three-terminal connection model, and compare the physical properties with two-terminal connection model, we emphasis on discussing the finding that symmetry of the system infects the conductance and local density, when the three terminals obey rotational symmetry, the conductance of the two output terminals is equal, while the local density is different slightly. When the three terminals don't obey rotational symmetry, though the energy of each conductance...