有机亚铁磁体的高自旋极化率实现机制及其自旋输运特性

The researches on the spin-dependent transport through the organic ferromagnets have already been performed, however, the researches on the spin-dependent transport through the organic ferrimagnets is just a new field. In comparison with the organic ferromagnets, the organic ferrimagnets possess much more complex electronic structures and richer mechanisms of the magnetic couplings, and under the quantum controlling of the external circumstances, they can exhibit much more sensitive responses to the temperature and the external magnetic fields. Thus, the organic ferrimagnets have wider and more potential applications of the organic spintronic devices with multiple functionalities. In this subject, by the means of the quantum statistic Green's function theory and the non-equilibrium Green's function theory combined with other theoretical methods, the mechanisms to realize the high or complete spin polarization in the organic ferrimagnets will be studied, and meanwhile, the multi-channel spin-dependent transport effects induced by the multiple organic radicals and conjoined bridges in them will be presented,the mechanisms of the spin-dependent coherence and decoherence will be determined. The relation between the the formation and evolution of the high-spin states and the low-spin states and the spin-dependent transport the organic ferrimagnets will be presented. And then, the effects of the electron-electron interaction, the electron-phonon couplings, the ferrimagnetic phase transition, the spin-Peierls phase transition, the formation and evolution of the solitions, polarons and bipolarons on the spin-dependent transport based on the organic ferrimagnets will be studied. Our research results can be applied to explain the corresponding experimental works in this field, and based on the above-mentioned studies, the basic concepts and the research contents in the organic spintronics will be enriched, developed and perfected, in particular, the results will show nice guides for the designs of the organic spintronic devices with the new and multiple functionalities.

关于有机铁磁体自旋输运的研究已经开展，但对有机亚铁磁体的自旋输运特性的研究，却是一个全新的研究领域。较有机铁磁体，有机亚铁磁体的电子结构和磁性耦合机理更加复杂；在外界调控下，表现出更敏感的温度和外场响应特性，因此，有机亚铁磁体在设计新型有机自旋器件方面，具有更为广阔的应用前景。本项目采用量子统计的格林函数和非平衡态格林函数方法，并结合其它理论方法，研究有机亚铁磁体高自旋极化率的实现机制；研究有机亚铁磁体由多自由基或多桥联体引起的自旋多通道隧穿效应，探索电子的相干与退相干机制；研究有机亚铁磁内高自旋态和低自旋态的形成、演化与其自旋输运间的关系；研究系统电子-电子关联、电子-声子耦合、亚铁磁相变及自旋-派尔斯相变、孤子与极化子等元激发准粒子的形成与演化对自旋极化输运的影响。我们的研究成果，将解释已有的实验，完善和发展有机自旋学的基本概念和研究内容，并为实验上设计新颖的有机自旋器件提供理论依据。

在国家自然科学基金的资助下，按照项目的研究计划，我们对有机亚铁磁体、有机磁性分子、石墨烯纳米带、DNA一维链以及二维量子系统的磁学、自旋电子学及自旋热电子学等进行了详系统地研究；同时，在该项目的资助下，我们开展了凝聚态前沿物理前沿课题的研究，如拓扑绝缘体、量子自旋霍尔效应、量子反常霍尔效应等，使得本课题的研究始终处于凝聚态物理学科前沿。对这些课题的研究，我们已取得了一些创新性的研究成果，主要有：（1）我们对一维DNA链的动力学行为进行了研究，发现DNA链在外加电压下，激发的电流将诱导链内电致力效应，增强了DNA链的动力学过程，并形成DNA泡结构，对生物定向打靶提供了理论依据；同时，我们对DNA热电性质进行了研究，得到了增强DNA链热电效率的物理机制；（2）我们对磁性单分子的热自旋Seebeck效应进行了研究，得到了磁性分子的自旋Seebeck的调控机制；（3）我们对基于石墨烯、硅烯、黑磷纳米带的热自旋电子学性质进行了研究，得到了一些新奇的热自旋电子学现象，如负微分的自旋Seebeck效应、热自旋庞磁阻效应、热自旋流过滤效应、热自旋整流效应和热自旋流开关效应等，特别是我们设计了自旋Seebeck二级管，同时我们将对该方向的研究推向器件应用，得到了同时具有负微分自旋Seebeck效应的自旋Seebeck二级管的理论设计；（4）此外，在本项目的资助下，我们还对拓扑绝缘体进行了研究，如有限尺寸效应对量子反常霍尔效应的影响，发现随着材料宽度减小，上下边缘态中的不同自旋态的耦合将不一样，使得量子反常霍尔效应有着增强的趋势，同时设计了一些新型的二维拓扑材料。研究成果以学术论文的形式在Nano. Lett.、2D Mater.、Phys. Rev. B、New J. Phys.、Nanoscale、Nanotechnology、Phys. Chem. Chem.Phys.、Sci. Rep.、Appl. Phys. Lett. 等学术刊物上发表。