Point vortices take a triangular lattice structure in a rotating system as a minimum energy state. We perform a numerical simulation of point vortex systems using initial conditions indicating that the triangular lattice is randomly perturbed. The total energy increases with the magnitude of the perturbation. When the energy is increased, the vortex lattice becomes irregular and a layered structure appears. When the energy is further increased, the layered structure disappears and a liquidlike state appears. We interpret the melting transition with a mean-field approximation for layered structures.
Molecular Dynamics of pancake vortices with realistic interactions: Observing the vortex lattice melting transition
在本文中，我们描述了一个版本的伦敦朗之万分子动力学模拟，允许在高度各向异性的高温超导体材料Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$的涡旋晶格熔化转变的调查。我们考虑了饼状涡之间的完全电磁相互作用和约瑟夫森相互作用。我们还在所有方向上实施周期性边界条件，包括沿其施加磁场的z轴。我们将展示如何实现通量切割和重连作为一个模拟的排列在多级Monte Carlo方案，并证明这一过程导致磁通纠缠扩散的涡旋液相。观察到的涡旋晶格的一阶熔化转变与以前的多级蒙特卡罗模拟非常一致。
On the melting of the nanocrystalline vortex matter in high-temperature superconductors
对高各向异性高温超导体Bi $_2$ Sr $_2$ CaCu $_2$ O $_8$中的涡旋物质进行了多能级蒙特卡罗模拟.我们引入了满足$B_ϕ\le B$的低浓度柱状缺陷。同时考虑了薄饼涡之间的电磁相互作用和约瑟夫森相互作用。纳米晶，纳米液体和均匀的液相被确定与实验一致。我们观察到的两步熔融过程，也注意到增强的结构因子之前的熔融过渡。提出的理论模型与我们的研究结果是一致的。
We study in this article properties of a nanodot embedded in a support by Monte Carlo simulation. The nanodot is a piece of simple cubic lattice where each site is occupied by a mobile Heisenberg spin which can move from one lattice site to another under the effect of the temperature and its interaction with neighbors. We take into account a short-range exchange interaction between spins and a long-range dipolar interaction. We show that the ground-state configuration is a vortex around the dot central axis: the spins on the dot boundary lie in the $xy$ plane but go out of plane with a net per…
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。
The iron-based superconductors are characterized by strong fluctuations due to high transition temperatures and small coherence lengths. We investigate fluctuation behavior in the magnetic iron-pnictide superconductor $\mathrm{Rb}\mathrm{Eu}\mathrm{Fe}_{4}\mathrm{As}_{4}$ by calorimetry and transport. We find that the broadening of the specific-heat transition in magnetic fields is very well described by the lowest-Landau-level scaling. We report calorimetric and transport observations for vortex-lattice melting, which is seen as a sharp drop of the resistivity and a step of the specific heat …
The hexatic fluid refers to a phase in between a solid and a liquid which has short range positional order but quasi-long range orientational order. In the celebrated theory of Berezinskii, Kosterlitz and Thouless and subsequently refined by Halperin, Nelson and Young, it was predicted that a 2-dimensional hexagonal solid can melt in two steps: first, through a transformation from a solid to a hexatic fluid which retains quasi long range orientational order and then from a hexatic fluid to an isotropic liquid. In this paper, using a combination of real space imaging and transport measurements …
A set of interacting vortices in $2D$ in the presence of a substrate with square symmetry and at filling ratio $1$ can display a low temperature solid phase where only one of the reciprocal lattice vectors of the substrate is present\cite{toby1,fasano}. This partially pinned vortex lattice melts to a modulated liquid via a continuous transition \cite{toby1}. Brownian dynamics simulation is carried out to study the behavior of driven partially pinned solid at different temperatures. The average vortex velocity for forces above the depinning threshold shows a non-monotonic behavior with temperat…
