发表机构
Department of Physics and Astronomy, University of Kentucky（肯塔基大学物理与天文学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究揭示二维超导体下临界场随尺寸变化的奇异规律，通过微观模型推导其标度关系，为二维超导体弱场热力学提供微观基础。
AI 中文摘要
在块状三维II型超导体中，孤立涡旋成为热力学有利态时的下临界场是与尺寸无关的材料属性。我们表明二维超导体的情况不同：超导体尺寸越大，产生第一个涡旋所需的磁场越弱。二维下的下临界场始终与尺寸相关。对于面积为$\boldsymbol{\textit{A}}$的圆盘，弱屏蔽 regime 下的下临界场$\boldsymbol{B_v(\textit{A})}$标度为$\boldsymbol{\textit{A}^{-1}\boldsymbol{\textit{ln}}(\textit{A}/\textit{A}_0)}$，强屏蔽 regime 下标度为$\boldsymbol{\textit{A}^{-1/2}}$。我们从一个解析易处理的微观模型推导出这些结果，该模型能描述磁场中均匀态和单量子化涡旋态的多体波函数，并通过将其长程二维超流电流与三维麦克斯韦方程耦合来纳入屏蔽效应。这些结果促使在$\boldsymbol{(1/\textit{A}, B)}$平面上组织二维超导体的弱场基态，原点代表零场热力学极限且具有奇异性。沿$\boldsymbol{B}$轴趋近原点会得到越来越稀疏的涡旋晶格，沿$\boldsymbol{1/\textit{A}}$轴趋近则得到均匀无涡旋态。我们的理论表明，携带固定有限通量的每条轨迹在热力学极限下最终都会趋近无涡旋态，为二维超导体的弱场热力学提供了坚实的微观基础。
英文摘要
In a bulk 3D type-II superconductor, the lower critical field at which an isolated vortex becomes thermodynamically favorable is a size-independent material property. We show that the situation is different in 2D superconductors: the larger the superconductor, the weaker the field needed to create its first vortex. The lower critical field in 2D is always size-dependent. For a disk of area $\mathcal A$, the lower critical field $B_v(\mathcal A)$ scales as $\mathcal A^{-1}\ln(\mathcal A/\mathcal A_0)$ in the weak-screening regime and as $\mathcal A^{-1/2}$ in the strong-screening regime. We derive these results from an analytically tractable microscopic model that admits many-body wavefunctions for both the uniform and singly quantized vortex states in a magnetic field, and incorporate screening by coupling their long-distance 2D supercurrents to 3D Maxwell equations. These results motivate organizing the weak-field ground-state of a 2D superconductor in the $(1/\mathcal A,B)$ plane. The origin represents the zero-field thermodynamic limit and it is singular. Approaching the origin along the $B$ axis leads to an increasingly dilute vortex lattice, whereas approaching along the $1/\mathcal A$ axis yields the uniform vortex-free state. Our theory shows that every trajectory carrying fixed finite flux ultimately approaches the vortex-free state in the thermodynamic limit and provides a firm microscopic foundation for the weak-field thermodynamics of 2D superconductors.
Comments10+34 pages
