Effects of width and relative position of electrode on transport properties of spintronic nanodevice

Abstract

Using nonequilibrium Green’s function combined with density functional theory, we investigate the spin-resolved transport properties of a single porphycene molecular device with the zigzag graphene nanoribbon electrodes from first-principles calculations. The calculated results show that the width and the relative position of the electrode play an important factor in the spin-resolved I–V characteristics of this molecular device. When a single porphycene molecule connects to electrodes straightly, the device exhibits a significant spin-filtering behavior with a nearly 100% spin filtering efficiency. In addition, negative differential resistance behavior can be observed in its β-spin I–V characteristic. The electrode widening can enhance the negative differential resistance behavior of the β-spin I–V characteristics, but weaken the spin filtering efficiency of the device at high bias voltages. When a single porphycene molecule connects to electrodes un-straightly, the β-spin currents increase linearly in the whole bias range and its I–V characteristics no longer show the negative differential resistance behavior. Moreover, the electrode widening can enhance both α-spin currents and β-spin currents evidently leading to the absent of the spin filtering characteristic.