在三维受抑XY模型下研究了强无序强II型超导体中涡旋的动力学行为。对于[Phys. Rev. Lett. { \bf 91}，077002（2003）]和[Phys. Rev. B { \bf 68}，220502（R）（2003）]中，通过进行大规模动力学模拟，提供了在未屏蔽极限中有限温度涡旋玻璃化转变的强有力证据。在两种模型中得到的关联长度指数和动力学指数彼此不同，也不同于三维玻璃规模型中的关联长度指数和动力学指数。此外，一个真正的连续脱钉过渡在零温度下观察到的两个模型。对退钉化转变的热圆化的标度分析表明，与最近的研究相反，在涡旋玻璃相中存在一种非Arrhenius型的蠕变运动。
英文摘要：
Dynamics of vortices in strongly type-II superconductors with strong disorder is investigated within the frustrated three-dimensional XY model. For two typical models in [Phys. Rev. Lett. {\bf 91}, 077002 (2003)] and [Phys. Rev. B {\bf 68}, 220502(R) (2003)], a strong evidence for the finite temperature vortex glass transition in the unscreened limit is provided by performing large-scale dynamical simulations. The obtained correlation length exponents and the dynamic exponents in both models are different from each other and from those in the three-dimensional gauge glass model. In addition, a genuine continuous depinning transition is observed at zero temperature for both models. A scaling analysis for the thermal rounding of the depinning transition shows a non-Arrhenius type creep motion in the vortex glass phase, contrarily to the recent studies..
Equilibrium First-Order Melting and Second-Order Glass Transitions of the Vortex Matter in Bi$_2$Sr$_2$CaCu$_2$O$_8$
通过测量存在涡旋“振动”时的局部\emph{equilibrium}磁化强度$M(H,T)$，绘制了BiPDMATHABMN Sr $_2$ CaCu $_2$ O $_8$的热力学$H-T$相图。两个同样尖锐的一级磁化步骤显示在一个单一的温度扫描，体现了液-固-液序列。此外，二阶玻璃化转变线显示的平衡$M(T)$斜率急剧突破。一阶和二阶线相交在中间温度，表明存在四个阶段：布拉格玻璃和涡旋晶体在低场，玻璃和液体在较高的领域。
At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster-crystal. In the present work we explore the out-of-equilibrium dynamics for a two-dimensional realization, which is relevant to superconducting materials with multi-scale intervortex forces. We find that for small temperatures following a quench, the suppression of the thermally-activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in term…
Absence of a True Vortex-Glass Phase above the Bragg Glass Transition Line in Bi-2212
在对Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$（Bi-2212）单晶的磁性测量中，发现在$S-H$和$S-T$曲线上都有一个具有动力学特征的通用峰，S为磁弛豫速率。在较高的磁场下，特征指数$μ$变为负值，结合$logE$与$ logj$的正曲率和基于二维涡旋玻璃理论或塑性蠕变理论的标度，我们得出结论：当$j\to 0$时，第二峰以上的涡旋运动是塑性的，在有限温度下Bi-2212中不存在涡旋玻璃相。S的峰值被解释为不同亚稳涡旋态之间的交叉。
The glass-like vortex distribution in pulsed laser deposited YBCO thin films is observed by scanning superconducting quantum interference device microscopy and analysed for ordering after cooling in magnetic fields significantly smaller than the Earth's field. Autocorrelation calculations on this distribution show a weak short-range positional order, while Delaunay triangulation shows a near-complete lack of orientational order. The distribution of these vortices is finally characterised as an isotropic vortex glass. Abnormally closely spaced groups of vortices, which are statistically unlikel…
We show that in type-II superconductors a magnetic field applied transversely to correlated columnar disorder, drives a phase transition to a distinct "smectic" vortex glass (SmVG) state. SmVG is characterized by an infinitely anisotropic electrical transport, resistive (dissipationless) for current perpendicular to (along) columnar defects. Its positional order is also quite unusual, long-ranged with true Bragg peaks along columnar defects and logarithmically rough vortex lattice distortions with quasi-Bragg peaks transverse to columnar defects. For low temperatures and sufficiently weak colu…
An epitaxial NdFeAs(O,F) thin film of 90 nm thickness grown by molecular beam epitaxy on MgO single crystal with Tc = 44.2 K has been investigated regarding a possible vortex glass-liquid tran-sition. The voltage-current characteristics show excellent scalability according to the vortex-glass model with a static critical exponent ν of around 1.35 and a temperature-dependent dynamic exponent z increasing from 7.8 to 9.0 for the investigated temperature range. The large and non-constant z values are discussed in the frame of 3D vortex glass, thermally activated flux motion, and inhomogeneity bro…
Evidence of first-order transition between vortex glass and Bragg glass phases in high-$T_{\rm c}$ superconductors with point pins: Monte Carlo simulations
本文用蒙特卡罗模拟研究了点钉存在下高$\vec{B}\parallel\vec{c}$超导体中涡旋玻璃相和布拉格玻璃相之间的相变。观察到有限的潜热和比热的$δ$函数峰，这清楚地表明这是一个热力学一级相变。熵跃变和林德曼数的值与熔化转变的值一致。层间相位差的大跳跃与Gaifullin { \it et al.}的Bi $_{2}$ Sr $_{2}$ CaCu $_{2}$ O $_{8+y}$的最近约瑟夫森等离子体共振实验一致。
Order-disorder transitions between glassy phases are quite common in nature and yet a comprehensive survey of the microscopic structural changes remains elusive since the scale of the constituents is tiny and in most cases few of them take part in the transformation. Vortex matter in type-II superconductors is a model system where some of the experimental challenges inherent to this general question can be tackled by adequately choosing the host superconducting sample. For instance, Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8 + δ}$ is a type-II superconductor with weak point disorder that presents a trans…
"Fragile superconductivity": a kinetic glass transition in the vortex matter of the high-temperature superconductor YBa2Cu3O7-d
在自然界中发现的许多不同种类的玻璃态中，自旋玻璃和结构玻璃（例如普通窗玻璃）可能受到最多的关注。关于玻璃态的中心问题之一是“玻璃”是否是不同于“液体”相的热力学相。据信，这实际上可能是自旋玻璃的情况，而结构玻璃中的玻璃化转变似乎主要是动力学性质的。然而，过冷结构液体表现出广泛的行为，可以使用Angell的“强-脆弱”方案进行分类，其中术语“强”和“脆弱”分别指Arrhenius和高度非Arrhenius松弛行为。对于极其脆弱的液体，不能排除玻璃化转变的热力学起源。然而，缺乏对导致不同程度的脆弱性和影响动力学玻璃化转变的复杂性的微观理解。此外，不同种类的玻璃态（自旋、结构等）之间的联系（如果有的话）还不清楚在这里，我们研究了一种新型的物质，即在高温超导体（HTSC）YBa 2 Cu 3 Ox的涡旋物质的玻璃态行为。
We analysed the flux-flow region of isofield magneto resistivity data obtained on three crystals of BaFe$_{2-x}$Ni$_x$As$_2$ with $T_c$$\sim$20 K for three different geometries relative to the angle formed between the applied magnetic field and the c-axis of the crystals. The field dependent activation energy, $U_0$, was obtained from the TAFF and modified vortex-glass models, which were compared with the values of $U_0$ obtained from flux-creep available in the literature. We observed that the $U_0$ obtained from the TAFF model show deviations among the different crystals, while the correspon…
Phase-coherence threshold and vortex-glass state in diluted Josephson-junction arrays in a magnetic field
本文数值研究了二维约瑟夫森结阵列中位相相干和涡旋玻璃态的相互作用，其中每个元胞的通量量子数平均为合理值$f$，并且结的稀释度是随机的。对于$f=1/2$，我们发现了一个相位相干阈值$x_s$的证据，低于稀释的路口$x_p$，超导过渡消失的渗滤浓度。对于$x_s < x < x_p$，阵列表现为在有限温度下具有非零线性电阻的零温度涡旋玻璃。零温临界电流在涡旋玻璃区对$f$的变化不敏感，而在相位相干区对$f$的变化有很强的依赖性。
A method is presented to solve the Bogoliubov-de Gennes equations with arbitrary distributions of vortices. The real-space Green's function approach based on Chebyshev polynomials is complemented by a gauge transformation which allows one to treat finite as well as infinite, ordered as well as disordered vortex configurations. This tool gives unprecedented access to vortex lattices at very low magnetic fields and glassy phases. After describing in detail the method and its implementation, we use it to address a series of problems related to $d$-wave superconductivity on the square lattice. We …
Study of dissipation processes in high-temperature superconductors of ErBa2Cu3O7-δ system near the superconductive transition critical temperature Tc in the range of possible Abrikosov vortex lattice melting
In this article, we present evidence for the existence of vortex-solid/glass (VG) to vortex-fluid (VF) transition in a type-II superconductor (SC), NbN. We probed the VG to VF transition in both 2D and 3D films of NbN through studies of magnetoresistance and current-voltage characteristics. The dynamical exponents corresponding to this phase transition were extracted independently from the two sets of measurements. The $H$-$T$ phase diagram for the 2D and 3D SC are found to be significantly different near the critical point. In the case of 3D SC, the exponent values obtained from the two indep…
We studied strong-coupling effect upon an isolated vortex in a two-dimensional chiral p-wave superconductor. We solved the Eilenberger equation for the quasiclassical Green's functions and the Eliashberg equation with single mode Einstein boson self-consistently. We calculated the free-energy of each obtained vortex, and found that a non-axisymmetric vortex metastably exists in some situation.
