长程自旋极化超流输运理论研究

This project mainly studies the dependence of the long-range spin-polarized supercurrent on the strength of the magnetization, the thickness of ferromagnetic layers and the structural symmetry of local magnetic moment in the superconductor-ferromagnet structures. We will construct the wave functions for spin-singlet and triplet pairs as well as their evolutionary model for quantum states. The results will clarify the root causes and the internal mechanisms about several experimental and theoretical anomalies in the superconductor-ferromagnet heterostructure junctions, such as remotely induced magnetism in a normal metal using a superconducting spin-valve; the phenomena about the changes of the superconducting subgap, the “0-π transition” et al induced by inhomogeneous magnetizations; gate-voltage control of the long-range spin-polarized supercurrent. It can help us to reveal basic law of long-range spin-polarized supercurrent transporting in superconductor-ferromagnet structure. The conclusion can provide the theoretical bases for the development of the spin-dependent quantum-coherence devices, and promotes the development of spintronics.

本项目主要研究超导-铁磁结构中长程自旋极化超流随铁磁体的磁化强度、铁磁层厚度、局域磁序结构对称性变化的物理过程和规律。我们将构造描述自旋单、三重对的波函数及其量子态演化模型，并探究超导-铁磁异质结中若干实验和理论反常现象的根本原因和内在机制，如:利用超导自旋阀在正常金属中远程诱导磁矩；非均匀磁矩引起的超导子能隙变化、“0-π态转变”等现象；栅压对长程自旋极化超流的调控作用。这些研究有助于揭示超导-铁磁结构中长程自旋极化超流输运的基本规律，为研制自旋相关的量子相干器件提供基本理论依据，推动自旋电子学发展。

本项目主要研究超导-铁磁异质结中非均匀铁磁结构对超导电性和长程超流的影响。我们构造了描述自旋单、三重对的波函数及其量子态演化模型,并利用该模型所得结果阐述了异质结中若干实验和理论反常现象的根本原因和内在机制，如：圆锥形交换场下的非均匀超导电性；一维圆锥形铁磁约瑟夫森结中形成的自发超流；正常金属/超导/铁磁-1/铁磁-2自旋阀结构中正常金属和超导区域内诱导的局域磁矩；铁磁层间的势垒对超导/双层铁磁/超导结中临界电流的调制作用。这些研究有助于揭示超导-铁磁结构中构成库珀对的纠缠电子的分布特征以及长程超流输运的基本规律。所得结论为研制超导量子相干器件提供了理论依据，推动了超导自旋电子学的发展。