Physica C-superconductivity and Its Applications最新文献

英文中文

Effect of winding pitches on screening current induced field of CORC cables 绕组螺距对屏蔽CORC电缆电流感应场的影响

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2026-01-27 DOI: 10.1016/j.physc.2026.1354836

Jian Cheng , Zhiyi Luo , Fengyin Zhang , Weili Zhao , Quan Zhang , Bangzhu Wang , Junhua Cheng

Conductor on round core (CORC) cables exhibit great potential for applications in large-scale high-field magnets of fusion and power transmission due to their high mechanical flexibility and large current capacity. However, both the ripple current in power transmission systems and the excitation/demagnetization processes in magnet applications inevitably generate alternating magnetic fields perpendicular to the tape surface. These fields induce screening currents and corresponding screening current induced field (SCIF) on the wide face of the tapes, which degrade the magnetic field uniformity and even mechanical or thermal stability in large-scale magnet applications. In this paper, a finite element numerical simulation based on the T–A formulation is employed to investigate the SCIF characteristics of CORC cables with different winding pitches at 77 K, 20 K, and 4.2 K. The numerical results show that the amplitude of the SCIF increases significantly with the ramp rate of the applied magnetic field. Moreover, both the peak and steady-state values of the SCIF increase notably with the winding pitch, exhibiting a clear monotonic trend. This study reveals the influence of winding pitches on the SCIF characteristics of CORC cables and provides a valuable reference for the structural optimization of conductors in large-scale high-field magnets.

圆芯电缆导体具有高机械柔韧性和大电流容量等优点，在大型高磁场磁体的融合和输电中具有很大的应用潜力。然而，无论是电力传输系统中的纹波电流，还是磁体应用中的激励/退磁过程，都不可避免地产生垂直于磁带表面的交变磁场。这些磁场会在磁带的宽表面产生筛选电流和相应的筛选电流感应场（SCIF），从而降低磁场均匀性，甚至降低大规模磁体应用中的机械或热稳定性。本文采用基于T-A公式的有限元数值模拟方法，研究了77 K、20 K和4.2 K时不同绕组节距的CORC电缆的SCIF特性。数值计算结果表明，随外加磁场斜坡率的增大，磁场梯度场的幅值显著增大。随着绕组节距的增大，scf的峰值值和稳态值均显著增大，且呈明显的单调趋势。本研究揭示了绕组螺距对CORC电缆SCIF特性的影响，为大型高场磁体导体结构优化提供了有价值的参考。

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引用次数: 0

Near-Tc vortex pinning and Dew–Hughes scaling in CaK(Fe1−xNix)4As4 and Ba(Fe1−xCox)2As2 single crystals CaK(Fe1−xNix)4As4和Ba(Fe1−xCox)2As2单晶的近tc涡旋钉钉和Dew-Hughes标度

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2026-01-20 DOI: 10.1016/j.physc.2026.1354834

N. Haberkorn , M. Xu , J. Schmidt , S.L. Bud’ko , P.C. Canfield

We compare pinning-force scaling in Fe-based superconductors exhibiting moderate vortex fluctuations using the Dew-Hughes formalism. Single crystals of CaK(Fe_1−xNi_x)₄As₄ (1144) and Ba(Fe_1−xCo_x)₂As₂ (122) are analyzed by fitting the normalized pinning force,

F_{p} / F_{p, m a x} = A h^{p} {(1 - h)}^{q}

, as a function of the reduced field

h = H / H_{i r r} (T)

near T_c, with the peak position at

h_{0} = p / (p + q)

. In 1144,

F_{p} (h)

data are well described by single-peak scaling with h₀ ≃ 0.30–0.34, consistent with predominant point-like disorder. In 122, h₀ shifts from ≈ 0.17–0.23 in underdoped crystals and to ≈ 0.37–0.40 near optimal doping, indicating a mixed δT_c/point pinning landscape. Literature datasets show that proton irradiation in lightly doped 1144 preserves a single peak near h₀ ≈ 0.33, whereas heavy-ion irradiation in near-optimally doped 122 produces a high-field shoulder. Overall, Dew-Hughes scaling captures the main trends phenomenologically and provides a practical map linking the effective peak position h₀ to the prevailing pinning landscape.

我们用Dew-Hughes的形式比较了铁基超导体中表现出中等涡旋波动的钉紧力尺度。对CaK(Fe1−xNix)4As4（1144）和Ba(Fe1−xCox)2As2（122）单晶进行分析，拟合归一化钉钉力Fp/Fp，max=Ahp(1−h)q作为Tc附近还原场h= h /Hirr(T)的函数，峰值位置为h0=p/(p+q)。在1144年，Fp(h)数据被单峰标度很好地描述为h0≃0.30-0.34，与主要的点状失序一致。在122中，h0从未掺杂晶体的≈0.17-0.23转变为接近最优掺杂时的≈0.37-0.40，表明δTc/点钉钉混合景观。文献数据显示，质子辐照在轻掺杂的1144中在h0≈0.33附近保留了一个单峰，而重离子辐照在接近最佳掺杂的122中产生了一个高场肩。总的来说，Dew-Hughes标度捕捉了现象上的主要趋势，并提供了一个实用的地图，将有效峰位置h0与主流钉钉景观联系起来。

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引用次数: 0

Vortex matter in labyrinthine configurations 迷宫结构中的涡旋物质

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2026-01-20 DOI: 10.1016/j.physc.2026.1354833

K. Rojas-Daza , J. Barba-Ortega , C.A. Aguirre , Clarence Cortés , P. Díaz , David Laroze

In this work, we investigate numerically the vortex dynamics in thin superconducting films patterned with labyrinthine geometries using numerical solutions of the time-dependent Ginzburg–Landau equations (

TDGL

). We analyzed three complementary scenarios: (i) in the absence of an external magnetic field (

H = 0.0

) under an applied direct current (

J

) and (ii) in the absence of an applied current (

J = 0.0

) but under an external magnetic field (

H

) and finally (iii) in the absence of an external magnetic field (

H = 0.0

) under an applied current with negative and positive polarity while varying the Ginzburg–Landau parameter (

κ = 2.0, 3.0, 4.0, 5.0, 6.0

). By generating maze-like domains through a randomized Kruskal algorithm and sweeping the applied magnetic field

H

, we determine the magnetization

M_{z}

and extract the first critical field

H_{1}

. Our simulations reveal a pronounced dependence of

H_{1}

on the underlying geometry of the labyrinth, showing that the intricate network of corridors significantly modifies the onset of vortex penetration. Current–voltage measurements obtained from the dynamics of

TDGL

reveal a clear variation in the critical current with the Ginzburg–Landau parameter (

κ

), highlighting the roles of coherence length and penetration depth in these confined structures. Despite the intentional breaking of spatial symmetry by the maze design, no superconducting diode effect is observed within the explored parameter space. Smaller labyrinth sections showed nearly zero magnetic penetration, preserving superconductivity at higher fields in agreement with Bean–Livingston barrier behavior.

在这项工作中，我们利用时间相关的金兹堡-朗道方程（TDGL）的数值解，对具有迷宫几何图形的超导薄膜中的涡旋动力学进行了数值研究。我们分析了三种互补的情况：(i)在施加直流电(J)的情况下没有外磁场（H=0.0）；（ii）在没有外加电流（J=0.0）但有外加磁场(H)的情况；最后（iii）在施加负极和正极电流的情况下没有外加磁场（H=0.0），同时改变金兹堡-朗道参数（κ=2.0,3.0,4.0,5.0,6.0）。通过随机化Kruskal算法生成迷宫状畴并扫描外加磁场H，确定磁化强度Mz并提取第一个临界场H1。我们的模拟揭示了H1的明显依赖于迷宫的基本几何形状，表明复杂的走廊网络显着改变了漩涡穿透的开始。从TDGL动力学中获得的电流-电压测量结果显示，临界电流与金兹堡-朗道参数（κ）有明显的变化，突出了相干长度和穿透深度在这些受限结构中的作用。尽管迷宫设计有意打破了空间对称性，但在探索的参数空间内没有观察到超导二极管效应。较小的迷宫部分显示出几乎为零的磁穿透，在较高的磁场下保持超导性，与Bean-Livingston势垒行为一致。

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引用次数: 0

Energy conservation and reversibility during thermodynamic changes of state in superconductors: Joule heat vs. magnetocaloric cooling 超导体热力学状态变化中的能量守恒和可逆性：焦耳热与磁热冷却

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2026-01-16 DOI: 10.1016/j.physc.2026.1354832

Andreas Schilling

In the Meissner phase of a superconductor, an external constant magnetic field is shielded by circulating persistent zero-resistance supercurrents that are formed by Cooper pairs. However, a thermodynamic change of state within this phase, such as cooling or heating, inevitably generates normal currents of thermally excited unpaired charge carriers, induced by the time-dependent variations in the local magnetic field. They not only lead to deviations of the magnetic-field distribution from textbook Meissner profiles but also cause dissipative Joule heating. This sharply contradicts the expected reversibility of a truly thermodynamic superconducting state, a fact that has largely been overlooked in the literature. We show that these normal currents also produce a magnetocaloric cooling, which in total instantaneously and precisely compensates for the dissipated heat, thus ensuring overall energy conservation and reversibility. However, the Joule heating and magnetocaloric cooling processes are spatially distinct and should therefore lead to temperature inhomogeneities. We quantify these effects assuming realistic material parameters and conclude that they are challenging to measure with current experimental techniques. Significant temperature gradients are expected only directly at the first-order transition to the superconducting state, where the discontinuous flux expulsion should induce normal currents that are much larger than those deep in the Meissner phase. We also argue that the underlying physics in superconductors is fundamentally identical to that of thermomagnetic generators, where electromechanical work can be extracted from magnetized matter subjected to thermal cycles, and where the magnetocaloric cooling is balanced by the heat supplied from an external thermal reservoir.

在超导体的迈斯纳相中，由库珀对形成的循环持久的零电阻超电流屏蔽了外部恒定磁场。然而，在这一阶段的热力学状态变化，如冷却或加热，不可避免地产生正常电流的热激发不成对载流子，在局部磁场的时变诱导。它们不仅会导致磁场分布偏离教科书上的迈斯纳剖面，而且会引起耗散焦耳热。这与预期的真正热力学超导状态的可逆性严重矛盾，这一事实在文献中很大程度上被忽视了。我们表明，这些正常电流也产生磁热冷却，这在总的瞬间和精确补偿散失的热量，从而确保整体节能和可逆性。然而，焦耳加热和磁热冷却过程在空间上是不同的，因此应该导致温度的不均匀性。我们量化这些影响假设现实的材料参数，并得出结论，他们是具有挑战性的测量与当前的实验技术。只有在一阶过渡到超导态时才会有显著的温度梯度，在超导态中，不连续的通量排出应该会产生比迈斯纳相深处大得多的正常电流。我们还认为，超导体的基本物理原理与热磁发电机的基本物理原理是相同的，其中机电功可以从受热循环的磁化物质中提取，并且磁热冷却由外部热源提供的热量来平衡。

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引用次数: 0

Multi-parameter optimization of SPS conditions for high-performance MgB2: A statistical approach 高性能MgB2的SPS条件的多参数优化：一种统计方法

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2026-01-14 DOI: 10.1016/j.physc.2026.1354831

Hasan Ağıl

Spark Plasma Sintering (SPS) temperature critically governs the microstructural development and superconducting performance of MgB₂ bulk superconductors. In this study, MgB₂ bulks were fabricated at different SPS temperatures, and their density, porosity, grain size, critical current density (J_c), and magnetic levitation properties were systematically evaluated. To move beyond conventional qualitative interpretations, Pearson correlation analysis, multiple linear regression, and principal component analysis (PCA) were jointly employed to quantitatively assess the relative and competing effects of microstructural parameters on J_c. The results demonstrate that densification is the dominant parameter controlling J_c at 20 K, exhibiting a strong positive correlation with superconducting and levitation performance, while porosity acts as the primary detrimental factor. Grain growth shows a secondary limiting effect by reducing flux pinning efficiency at higher sintering temperatures. Multiple linear regression confirms density as the most influential predictor of J_c. In contrast, PCA reveals that SPS temperature, density, and J_c cluster along a common high-performance axis, distinct from grain size–related mechanisms. These findings provide a quantitative, data-driven framework for understanding SPS-induced performance optimization in MgB₂ and offer broader insights into processing–structure–property relationships in bulk superconductors.

火花等离子烧结（SPS）温度对MgB2块体超导体的微观结构发展和超导性能起着至关重要的作用。本研究在不同的SPS温度下制备了MgB2块体，并对其密度、孔隙度、晶粒尺寸、临界电流密度（Jc）和磁悬浮性能进行了系统的评价。为了超越传统的定性解释，我们联合使用Pearson相关分析、多元线性回归和主成分分析（PCA）来定量评估微观结构参数对Jc的相对影响和竞争影响。结果表明：致密化是20 K下控制合金Jc的主要参数，与超导性能和悬浮性能呈正相关，而孔隙度是主要的不利因素。在较高的烧结温度下，通过降低助焊剂钉接效率，晶粒生长表现出二次限制效应。多元线性回归证实密度是Jc最具影响的预测因子。相比之下，PCA显示SPS温度、密度和Jc沿着一个共同的高性能轴聚集，不同于晶粒尺寸相关的机制。这些发现为理解sps诱导的MgB2性能优化提供了一个定量的、数据驱动的框架，并为块状超导体的加工-结构-性能关系提供了更广泛的见解。

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引用次数: 0

Foreword for the special issue of Physica C “Quantum Matter” dedicated to Jan Zaanen 《物理学》特刊《量子物质》的前言，献给Jan Zaanen

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2026-01-01 DOI: 10.1016/j.physc.2025.1354822

引用次数: 0

Temperature equalization control method for rotor magnet of HTS synchronous condenser with circulating cold helium gas 冷氦循环高温超导同步冷凝器转子磁体的温度均衡控制方法

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2025-12-26 DOI: 10.1016/j.physc.2025.1354825

Xin Chen , Lei Wang , Cong Wang , Shixian Liu , Jianhua Liu , Gongxuan Chen , Hui Wang , Huangfang Wu , Jiancheng Zhang , Qiuliang Wang

In the cooling system of high-temperature superconducting (HTS) synchronous condenser rotor magnets, cold helium gas serves as the primary cooling medium. The complex coupling relationships among its flow rate, temperature, and pressure require precise control to address the instability caused by localized hotspots in the superconducting magnets.This paper integrates the singular perturbation control theory of variable-domain Smith to construct a mathematical model of the cold helium gas circulating cooling system.The cold helium gas circulation cooling system is decomposed into fast and slow subsystems. By precisely controlling the flow rate and velocity of the cold helium gas, the goal of eliminating local hotspots and achieving uniform temperature distribution in the superconducting magnet is realized.Simultaneously, the system performance is optimized using fuzzy adaptive PID control.In addition, a simulation experiment was conducted on the cold helium gas circulation cooling system of the superconducting magnet using this method, which verified the effectiveness of the aforementioned approach in eliminating local hotspots and improving temperature uniformity.This study provides an engineering-feasible optimization scheme for the cryogenic thermal management of the rotor magnet in HTS synchronous condensers.

在高温超导（HTS）同步冷凝器转子磁体冷却系统中，冷氦气是主要冷却介质。其流量、温度和压力之间复杂的耦合关系需要精确控制，以解决超导磁体局部热点引起的不稳定性。结合变域Smith的奇异摄动控制理论，建立了冷氦气循环冷却系统的数学模型。冷氦气循环冷却系统分为快、慢两个子系统。通过精确控制冷氦气的流量和速度，实现了消除超导磁体局部热点，实现超导磁体温度分布均匀的目标。同时，采用模糊自适应PID控制对系统性能进行优化。并利用该方法对超导磁体冷氦气循环冷却系统进行了仿真实验，验证了该方法在消除局部热点、提高温度均匀性方面的有效性。本研究为高温超导同步冷凝器转子磁体的低温热管理提供了一种工程可行的优化方案。

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引用次数: 0

Robust s±-wave pairing in a bilayer two-orbital model of pressurized La3Ni2O7 without the γ Fermi surface 无γ费米表面的加压La3Ni2O7双层双轨模型中的稳健s±波配对

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2025-12-19 DOI: 10.1016/j.physc.2025.1354824

Yi Gao

We studied the superconducting pairing symmetry based on a newly constructed tight-binding model of La

_{3}

_{2}

_{7}

under pressure, where the

γ

band sinks below the Fermi level and does not form the Fermi surface. The superconducting pairing symmetry is

s_{\pm}

-wave and is robust against the variation of the interaction strength. In this model, although the

γ

and

δ

bands are away from the Fermi level, the superconducting pairing function on them is not tiny. Instead, since the top of the

γ

band and bottom of the

δ

band are both located at

\sim

500 meV away from the Fermi level, and they are almost nested by the peak structure in the spin fluctuation, thus by forming an anti-phase pairing function on them, these two bands act constructively to superconductivity. Finally with detailed derivation and numerical calculation, we demonstrate that the Fermi surface approximated Eliashberg equation may lead to deviation of the pairing symmetry.

我们基于新建立的La3Ni2O7在压力下的紧密结合模型研究了超导对对称性，其中γ带下沉到费米能级以下并且不形成费米表面。超导对对称性为s±波，对相互作用强度的变化具有较强的鲁棒性。在该模型中，虽然γ带和δ带远离费米能级，但它们上的超导配对作用并不小。相反，由于γ带的顶部和δ带的底部都位于距离费米能级约500 meV的位置，并且它们在自旋涨落中几乎被峰值结构嵌套，因此通过在它们上形成反相配对函数，这两个带对超导性起着积极的作用。最后通过详细的推导和数值计算，证明了费米曲面近似Eliashberg方程可能导致对对称性的偏离。

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引用次数: 0

Can a superconductor charge a battery? 超导体能给电池充电吗？

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2025-12-18 DOI: 10.1016/j.physc.2025.1354823

J.E. Hirsch

To charge a battery it is necessary to know the difference between positive and negative charges. We argue that a superconductor described by the conventional theory of superconductivity does not know the difference between positive and negative charges, therefore it cannot charge a battery. Instead, a superconductor described by the theory of hole superconductivity can. We argue that existing experiments can be interpreted to imply that real superconductors can charge batteries, which undermines the credibility of the conventional theory. We propose a new experiment that can establish whether or not real superconductors are described by the alternative theory of hole superconductivity.

要给电池充电，必须知道正电荷和负电荷的区别。我们认为，传统的超导理论所描述的超导体不知道正电荷和负电荷的区别，因此它不能给电池充电。相反，由空穴超导理论描述的超导体可以。我们认为，现有的实验可以解释为暗示真正的超导体可以给电池充电，这破坏了传统理论的可信度。我们提出了一个新的实验，可以确定是否真正的超导体是由空穴超导的替代理论描述的。

引用次数: 0

Negative magnetoresistance in superconducting stripes 超导条纹中的负磁阻

IF 1 3区物理与天体物理 Q4 PHYSICS, APPLIED

Physica C-superconductivity and Its Applications

Pub Date : 2025-12-04 DOI: 10.1016/j.physc.2025.1354821

B.Ya. Shapiro , Baruch Rosenstein , Guy Leshem

For superconducting wires with small diameters quantum phase slippage is an important process which can yield a non-vanishing wire resistance down to very low temperatures. The effect of negative magnetoresistance for thin superconducting wire was considered in a simple model. One can conclude that the negative magnetoresistance in wires (narrow channels) are caused by decreasing number of the PSC due to interaction with entered and pinned inside Abrikosov vortices. With a subsequent increase in the magnetic field, the Abrikosov vortices replacing the phase slip centers making the main contribution to the magnetoresistance, which changes sign and becomes positive. The theory is in a good agreement with experiments.

对于小直径超导导线来说，量子相滑移是一个重要的过程，它可以在很低的温度下产生不消失的导线电阻。在一个简单的模型中考虑了超导细导线负磁电阻的影响。可以得出结论，导线（窄通道）中的负磁电阻是由于与进入和固定在Abrikosov漩涡内的PSC相互作用而导致的PSC数量减少引起的。随着磁场的增大，Abrikosov涡旋取代相滑中心成为磁阻的主要贡献，磁阻变符号为正。理论与实验很吻合。

引用次数: 0

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