Theoretical study on vortex states in superconductors

第二类超导体中的De Haas-van Alphen效应理论我们对第二类超导体中的De Haas-van Alphen振荡进行了数值和分析研究。我们推导了涡旋态下观察到的额外衰减的解析公式，该公式也可以用来估计与带隙和/或角度相关的带隙各向异性。基于Ginzburg-Landau方程，在相变温度附近，我们对超流体^3He的涡晶格结构进行了理论研究，给出了完整的相图。我们还预测了三分量旋量玻色-爱因斯坦凝聚体的新的涡旋结构。Maki参数的计算Maki参数是第二类超导体中最基本的量之一，它与相变时的比热跃迁，即Magn…斜率的变化有关我们对它进行了详细的研究，表明它与费米面的详细结构有很强的依赖关系，特别是在Dean材料中。第二类超导体上临界场的计算上临界场H&lt；c2&gt；是第二类超导体中最基本的量之一。很早就知道，清洁样品的H&lt；c2&gt；取决于详细的费米面结构。然而，目前还没有进行详细的计算。我们推导了一个H&lt；c2&gt；方程，它使我们能够利用费米面从第一性原理电子结构计算中定量地计算H&lt；c2&gt；。利用它，我们对Nb、NbSe_2和MgB_2的H&lt；c2&gt；进行了详细的研究，得到了与实验很好的定量一致。计算了H&lt；c2&gt；附近的第二类超导体的磁通流电阻率。我们对上临界场附近的磁通-流电阻率进行了详细的计算，以阐明总体温度和杂质浓度的依赖关系。较少

Theory of the de Haas-van Alphen effect in type-II superconductorsWe performed numerical and analytical studies of the de Haas-van Alphen oscillation in type-II superconductors. We derived an analytic formula for the extra attenuation observed in the vortex state, which can also be used to estimate the band and/or angle dependent gap anisotropy. Using it, we estimated gap amplitude of several materials.Vortex structures of superfluid ^3He and spinor Base-Einstein condensatesBased on the Ginzburg-Landau equations near the transition temperature, we performed a theoretical study on the vortex-lattice structures of superfluid ^3He in rapid rotation to present an entire phase diagram. We also predicted novel vortex structures of the three-component spinor Bose-Einstein condensate.Calculation of the Maki parameterThe Maki parameter is one of the most basic quantities in type-II superconductors which is relevant to the specific-heat jump at the transition, the change in the slope of the magn … More etization curve at the transition, etc. We performed a detailed study on it to show that it has a strong dependent on the detailed Fermi-surface structures, especially in dean materials.Calculation of the upper critical field of type-II superconductorsThe upper critical field H_<c2> is one of the most basic quantities in type-II superconductors. It has been knownn for a long time that H_<c2> of clean samples depends on the detailed Fermi-surface structures. However, few detailed calculations have been performed yet. We derived an H_<c2> equation which enables us to calculate H_<c2> quantitatively by using Fermi surfaces from first-principles electronic-structure calculations. Using it, we performed detailed studies on H_<c2> of Nb, NbSe_2, and MgB_2 to find excellent quantitative agreements with experiments.Calculation of the flux-flow resistivity of type-II superconductors near H_<c2>The electronic resistance in the vortex state of type-II superconductors is a complicated phenomenon involving the motion of vortices which has not been understood sufficiently. We performed a detailed calculation on this flux-flow resistivity near the upper critical field to clarify the overall temperature and impurity-concentration dependences. Less