封面文章

Hall anomalies in the centrosymmetric triangular-lattice antiferromagnet GdGa₂

Sidi Wang(王思迪), Jiyuan Li(李纪源), Yuhao Wang(王宇豪), Keqi Xia(夏克奇), Jing Meng(孟婧), Bocheng Yu(余博丞), Yiqian Hu(胡艺骞), Zheng Li(李峥), Hui Zhang(张慧), Jingzhong Luo(罗晶中), Dongmei Jiang(蒋冬梅), Qingfeng Zhan(詹清峰), Tian Shang(商恬), and Yang Xu(徐杨)

Chin. Phys. B, 2026, Vol. 35(2): 027502    

文章亮点介绍

磁斯格明子因其在未来自旋电子器件中的应用潜力而备受关注。传统上斯格明子存在于非中心对称材料中，但近期研究表明，中心对称体系中竞争磁相互作用同样可以诱导形成斯格明子。GdGa₂作为一种新近发现的中心对称三角格子反铁磁材料，理论预言其可能在特定磁场区间存在具有极短磁周期的Néel型斯格明子，有望应用于超高密度信息存储。

本文系统研究了GdGa₂及对比样品TbGa₂单晶的磁性与电输运性质。实验发现，在反铁磁有序态下，GdGa₂的霍尔电阻率在中磁场区间出现无法用传统双带模型描述的异常信号，该区间与前期共振弹性X射线散射实验确定的可能存在斯格明子的A相区域高度吻合。该霍尔异常幅度约为，可能源于自旋纹理诱导的贝里相位产生的拓扑贡献。相比之下，TbGa₂未观察到类似异常。本研究为中心对称体系中潜在斯格明子材料GdGa₂提供了重要的输运证据，为探索超短周期斯格明子在低功耗、高密度存储器件中的应用提供了新的材料平台。

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Fig. 5. (a) Hall resistivity ρ_xy(H) of GdGa₂ at T=2 K (H || c). Thick red curve shows the two-band fit for  μ₀H < 2.5 T and > 5.5 T using Eqs. (2) and (3). Thin red curve represents the extrapolation to the full field range (0–7 T). (b) Absolute residual |Δρ_xy'| at 2 K. (c) Temperature-dependent |Δρ_xy(H)'| for GdGa₂. Arrows indicate the direction of increasing temperature. (d) Magnetization M(H) hysteresis at the indicated temperatures (solid: descending field; dashed: ascending field). Grey lines mark the critical fields H_c1 and H_c2. (e) Magnetoresistance MR(H) at selected temperatures. Grey lines indicate kink positions corresponding H_c1  and H_c2. (f) Magnetic phase diagram with |Δρ_xy'| shown as a colormap. The color scale is optimized to highlight regions with enhanced |Δρ_xy'|. Phase boundaries, denoted by dashed grey lines, are estimated visually and serve as a guide to the eye. The enhancement of |Δρ_xy'| within the H_c1–H_c2 range aligns with the A-phase region, consistent with the A1- and partially the A2-phases reported in Ref. [25].

亮点文章

Pressure-induced superconductivity in kagome metal CsCr₃Sb₅: Role of spin–orbit coupling and inter-orbital spin fluctuations

Wei Wang(王巍), Shun-Li Yu(于顺利), and Jian-Xin Li(李建新)

Chin. Phys. B, 2026, 35(2):027401

文章亮点介绍

笼目晶格体系因其特殊的几何和电子结构，已成为探索非常规超导与新奇量子物态的重要平台。近期发现的笼目金属 CsCr₃Sb₅ 在常压下呈现电荷密度波、自旋密度波及轨道向列序等多种有序态的竞争与共存，并在压力下出现超导电性，为研究多自由度耦合与非常规超导提供了理想载体。

本文通过构建有效四轨道紧束缚模型，结合无规相位近似（RPA）方法，系统研究了压力条件下 CsCr₃Sb₅ 的超导配对对称性与微观机理。结果表明，Hund耦合会显著增强轨道间的自旋涨落，进而驱动体系形成具有 E_2g 对称性的超导能隙。分析进一步揭示，源自 Cr 原子d_x²_–y²轨道的 β 能带在这一配对过程中起到了核心作用，而自旋轨道耦合的引入可通过增强轨道涨落进一步稳定E_2g 配对对称性。本文从理论上预言了 CsCr₃Sb₅ 中非常规超导的配对对称性与配对机制，揭示了多轨道笼目体系中自旋与轨道自由度协同效应的重要性，为理解笼目体系及其他多轨道强关联超导体的物理性质提供了重要理论参考。

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Fig. 1. (a) Superconducting gap function in the A_2g channel. (b), (c) Two degenerate gap functions in the E_2g channel. (d), (g) Maximum eigenvalues of the particle-hole susceptibility χ(q,0). The black line denotes the boundary of the first Brillouin zone, and the white arrows mark the wave vectors corresponding to susceptibility maxima. (e), (h) Static spin susceptibilities and eigenvalues. Both bare and dressed spin susceptibilities are scaled by 1/18, with the dressed susceptibilities further shown on a logarithmic scale. Arrows highlight the positions of the prominent peaks. The inset in (e) shows a zoomed-in view of the bare susceptibilities. (f), (i) Singlet component of the pairing kernel for the A_2g and E_2g channels, respectively. The parameters sets (J_H/U, U, λSOC) used in (d), (e), (f) and (g), (h), (i) are the same as those in (a) and (b), (c), respectively.

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Electronic structure and superconducting gap of HgBa₂Ca₂Cu₃O_8+δ revealed by laser-based angle-resolved photoemission spectroscopy

Taimin Miao(苗泰民), Wenshan Hong(洪文山), Qinghong Wang(汪清泓), Shanshan Zhang(张珊珊), Bo Liang(梁波), Wenpei Zhu(朱文培), Neng Cai(蔡能), Mingkai Xu(徐明楷), Shenjin Zhang(张申金), Fengfeng Zhang(张丰丰), Feng Yang(杨峰), Zhimin Wang(王志敏), Qinjun Peng(彭钦军), Zuyan Xu(许祖彦), Hanqing Mao(毛寒青), Zhihai Zhu(朱志海), Xintong Li(李昕彤), Guodong Liu(刘国东), Lin Zhao(赵林), Yuan Li(李源), and X. J. Zhou(周兴江)

Chin. Phys. B, 2026, Vol. 35(2): 027402 

文章亮点介绍

自1986年铜氧化物高温超导体发现以来，理解高温超导机理和进一步提高超导转变温度一直是凝聚态物理研究中的核心问题。汞系铜氧化物超导体HgBa₂Ca₂Cu₃O_8+δ (Hg1223) 具有铜氧化物超导体中最高常压超导转变温度（T_c = 134 K），是探索高温超导机制及其高转变温度起源的理想体系。 然而，由于该材料缺乏自然的解理面，获得稳定且高质量的表面极具挑战，导致相关的电子结构研究十分匮乏。

本文利用自主研制的具有空间分辨的高分辨率激光角分辨光电子能谱系统（ARPES），对最佳掺杂Hg1223超导样品进行了测量。通过实空间扫描成像，在解理表面上识别出了两种区域：一个是仅能观测到单个费米面的“单费米面区域”；另一个是能够分辨出分别来自内层（IP）和外层（OP）铜氧面对应费米面的‘双费米面区域’。实验发现，在这两种情况下，观测到的电子态都主要集中在节点（nodal）区域附近。此外，本文对这两个区域的电子结构和超导能隙均进行了测量，超导能隙随动量的演变均偏离了标准的 d 波形式。

这些结果表明，Hg1223 的表面电子结构行为更接近于欠掺杂铜氧化物，这些发现为进一步深入理解高温超导体系的本征物理机理指明了实验方向。

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Fig. 1.Spatially resolved ARPES measurements on different cleavage surfaces of Hg1223. (a) Crystal structure of the trilayer cuprate Hg1223, consisting of three CuO₂ planes per unit cell. The inner CuO₂ plane (IP) is sandwiched between two outer planes (OPs) separated by Ca layers. The right panel illustrates several possible cleavage planes (HgO_δ, BaO or CuO₂).  (b) AC magnetic susceptibility measurement under a 10 Oe field showing a sharp superconducting transition at T_c = 133 K with a transition width (10 %-90 %) of 2.5 K. (c) Real space photocurrent map acquired by point-by-point scanning the sample surface. Two kinds of regions with distinct Fermi surface topology are observed on the surface. (d) Fermi surface mapping obtained from Region 1 (red circle in c) where only a single Fermi surface near the nodal region is observed. To enhance the covered momentum space, we measurement was carried out by applying a bias voltage of -90 V on the sample. (e) Fermi surface mapping obtained from Region 2 (blue circle in c) where two Fermi surface sheets near the nodal region are observed. The measurement was also performed under a -90 V sample bias.

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