London theory of the crossing vortex lattice in highly anisotropic layered superconductors
London theory of the crossing vortex lattice in highly anisotropic layered superconductors
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高度各向异性层状超导体中交叉涡晶格的伦敦理论
DOI：
10.1103/physrevb.64.094521
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发表时间：
2001
影响因子：
3.7
通讯作者：
K. Kadowaki
中科院分区：
文献类型：
--
作者：
S. Savel’ev;J. Mirković;K. Kadowaki
基于各向异性的伦敦理论，提出了一种新的描述由煎饼涡穿过的约瑟夫森涡(JVS)。对于PVs间距为$a$的致密($a\lambda_J$)PV晶格和非线性JV芯尺寸$\lambda_J$，计算了JV及其能量的场分布。结果表明，在较高的平面外磁场中形成的“移位”PV晶格(PV主要沿交错涡旋结构中的JV位移)在一定磁场下转变为被JV子晶格“俘获”的PV晶格，其中$Ph0是通量量子，$伽马是各向异性参数，$S$是CuO$2$面间的距离.
在面内磁场较低或较高的情况下，随着面内磁场的进一步减小，当面内磁场较低(B_x<；\Gamma\Phi_0/\lambda_{ab}^2)或较高($B_x\gtrsim\Phi_0/\Gamma S^2$)时，在面内穿透深度为$_(B_x<；\Gamma\Phi_0/\lambda_{ab}^2)的情况下，交叉涡旋晶格结构(PV和JV子晶格分别共存)的自由能可超过倾斜晶格(普通PV-JV涡旋结构)的自由能。这意味着交错涡旋结构是在中间场取向上实现的，而如果磁场靠近$c和$ab平面排列，则可以存在倾斜的涡旋晶格。在中间面内磁场$\Gamma\Phi_0/\lambda_{ab}^2\less sim B_x\less sim\Phi_0/\Gamma S^2$中，由于在位于$ab平面附近的磁场中，与倾斜的涡旋结构相比，在接近$ab平面的磁场中，交叉的涡旋结构似乎稳定下来，直到发生锁定转变，因为这种结构的能量比倾斜的涡旋结构低。
A novel description of Josephson vortices (JVs) crossed by the pancake vortices (PVs) is proposed on the basis of the anisotropic London theory. The field distribution of a JV and its energy have been calculated for both dense ($a \lambda_J$) PV lattices with distance $a$ between PVs, and the nonlinear JV core size $\lambda_J$. It is shown that the ``shifted'' PV lattice (PVs displaced mainly along JVs in the crossing vortex lattice structure), formed in high out-of-plane magnetic fields transforms into the PV lattice ``trapped'' by the JV sublattice at a certain field, lower than $\Phi_0/\gamma^2s^2$, where $\Phi_0$ is the flux quantum, $\gamma$ is the anisotropy parameter and $s$ is the distance between CuO$_2$ planes.
With further decreasing $B_z$, the free energy of the crossing vortex lattice structure (PV and JV sublattices coexist separately) can exceed the free energy of the tilted lattice (common PV-JV vortex structure) in the case of $\gamma s<\lambda_{ab}$ with the in-plane penetration depth $\lambda_{ab}$ if the low ($B_x<\gamma\Phi_0/\lambda_{ab}^2$) or high ($B_x\gtrsim \Phi_0/\gamma s^2$) in-plane magnetic field is applied. It means that the crossing vortex structure is realized in the intermediate field orientations, while the tilted vortex lattice can exist if the magnetic field is aligned near the $c$-axis and the $ab$-plane as well. In the intermediate in-plane fields $\gamma\Phi_0/\lambda_{ab}^2\lesssim B_x \lesssim \Phi_0/\gamma s^2$, the crossing vortex structure with the ``trapped'' PV sublattice seems to settle in until the lock-in transition occurs since this structure has the lower energy with respect to the tilted vortex structure in the magnetic field ${\vec H}$ oriented near the $ab$-plane.