AI 中文总结
研究超导薄膜条中涡旋进入电流与去配对电流，通过脏极限乌萨德尔理论的固定电流吉布斯泛函从微观角度重新审视问题，对零外场下理想均匀薄膜条带研究其无涡旋态稳定性，发现势垒消失电流与去配对电流精确重合。
AI 中文摘要
在珀尔-伦敦理论中，通常将涡旋进入超导条带时的电流与边缘势垒的消失联系起来。本研究从微观角度重新审视该问题，将其视为无涡旋载流态局部稳定性的丧失，运用脏极限乌萨德尔理论的固定电流吉布斯泛函，该理论在任意温度下均有效。对于零外场下忽略自场效应的理想均匀薄膜条带，研究了无涡旋态对空间均匀和非均匀微扰的稳定性。结果表明，势垒消失电流由均匀微扰确定，且与去配对电流精确重合。
英文摘要
The vortex-entry current density $J_{\rm v}$ of a superconducting strip is usually defined, within phenomenological Pearl--London theory, as the current density at which the edge barrier for vortex entry disappears. In that approach, $J_{\rm v}$ depends on a short-distance core cutoff introduced by hand, and its temperature dependence cannot be determined within the same framework. To remove this cutoff ambiguity and determine the temperature dependence, one needs a microscopic calculation of the vortex-entry current. Nevertheless, such a microscopic calculation has never been carried out. Here, we formulate and solve this problem for an ideal homogeneous dirty-limit superconducting thin-film strip at zero applied field, with self-field effects neglected. Vortex entry is treated as the loss of local stability of the vortex-free current-carrying state. The calculation uses the fixed-current Gibbs functional of Usadel theory, which is valid over the full temperature range $0<T<T_c$, and examines both spatially uniform and nonuniform perturbations. The microscopic calculation shows that the condition for disappearance of the vortex-entry barrier is identical to the depairing condition. The central result is not merely that two current densities have the same value. The criterion for disappearance of the vortex-entry barrier and the depairing criterion are not independent conditions. Both identify the same loss of local stability of the vortex-free current-carrying state, namely, the same spinodal. Consequently, $J_{\rm v}(T)=J_{\rm dp}(T)$ for all $0<T<T_c$. This result determines the temperature dependence of $J_{\rm v}$, removes the Pearl--London core-cutoff ambiguity, and establishes the microscopic equivalence of the vortex-entry and depairing current criteria.
Comments6 pages, no figures
