基于石墨烯电极的Co-Salophene分子器件的自旋输运

采用基于非平衡格林函数结合第一性原理的密度泛函理论的计算方法,研究了基于锯齿型石墨纳米带电极的Co-Salophene分子器件的自旋极化输运性质.计算结果表明,当左右电极为平行自旋结构时,自旋向上的电流明显大于自旋向下的电流,自旋向下的电流在-1V,1V]偏压下接近零,分子器件表现出优异的自旋过滤效应.与此同时,在自旋向上电流中发现负微分电阻效应.当左右电极为反平行自旋结构时,器件表现出双自旋过滤和双自旋分子整流效应.除此之外,整个分子器件还表现出较高的巨磁阻效应.通过分析器件的自旋极化透射谱、局域态密度、电极的能带结构和分子自洽投影哈密顿量,详细解释该分子器件表现出众多特性的内在机理.研究结果对设计多功能分子器件具有重要的借鉴意义.

Spin-dependent transport properties of a Co-Salophene molecule between graphene nanoribbon electrodes

Molecular spintronics has attracted much attention because of many novel functionalities at the single molecule level over the past decades.Recently,much research has focused on organic molecules containing transition metals in the field of molecular spintronics,which possesses desired spin-dependent transport properties for spintronic device applications. In this paper,based on non-equilibrium Green's function formalism combined with the first-principles density functional theory,the spin-dependent transport properties of an organic Co-Salophen molecule sandwiched between two zigzag graphene nanoribbon (ZGNR) electrodes are investigated.By applying an external magnetic field,the spin directions of the left and right ZGNR electrodes may be switched to two different configurations:the parallel (P) and antiparallel (AP) spin configurations.It is found that for the P spin configuration,the spin-up current is significantly larger than the spin-down one which is nearly zero in a bias range from -1.0 V to 1.0 V,exhibiting a nearly perfect spin filtering effect (up to 100%).Moreover,the spin-up current shows negative differential resistance behavior at ±0.3 V.For the AP spin configuration,the spin-down current is much larger than the spin-up one at the positive bias.On the contrary,the spinup current is much larger than the spin-down one at the positive bias.Therefore,the device exhibits bipolar spin filtering effect.It is also found that the spin-up current at the negative bias is much larger than that at the corresponding positive bias,while the spin-down current at the negative bias is much smaller than that at the corresponding positive bias,which shows the outstanding spin rectifying effect.Besides,a significant giant magnetoresistance effect is also obtained in the device when the spin directions of the left and right ZGNR electrodes switch between P and AP spin configurations. The spin transport properties of the device under P and AP spin configurations are attributed to the different orbital symmetries of spin subbands (π^* and π) of the electrodes and the spatial distribution of molecular orbitals within the bias window.By analyzing the spin-polarization transmission spectrum,the local density of states,the band structures and symmetries of the ZGNR electrodes and the projected self-consistent Hamiltonian states of molecular orbitals,the internal mechanism for multiple functional characteristics of the device is explained in detail.Our results indicate the Co-Salophen molecule can be a promising candidate for future applications in molecular spintronics device,and also provide a theoretical reference for designing the next-generation molecular nano-devices.