封面文章

A metastable state mediates the surface disordering of ice Ih

Zixiang Yan(颜子翔), Jiani Hong(洪嘉妮), Ye Tian(田野), Tiancheng Liang(梁天成), Limei Xu(徐莉梅), and Ying Jiang(江颖)

Chin. Phys. B, 2026, Vol. 35(1): 016804

文章亮点介绍

冰表面的预融化是指在低于体相熔点的温度下，冰表面出现结构无序化并形成准液态层的过程，该现象在冰川动力学、冰表面摩擦及表面化学反应等宏观和微观过程中具有重要影响。阐明冰表面预融化的初始结构及其演化过程对理解预融化的物理机制有重要意义。本文利用 qPlus 型低温原子力显微镜，对冰 Ih (0001) 表面在不同温度和水分子沉积气压下的结构无序化过程进行了系统的原子尺度研究。

本研究发现，冰表面的亚稳态平面局域结构（PLS）能够在预融化早期阶段充当无序化的“种子”，促进其周围约 2 nm²的区域发生无序化。同时，在表面晶化温度（T_c） 以上的预融化区域和T_c以下的低温动力学区域，冰表面呈现出高度相似的微观无序特征。此外，本研究还发现随着水分子沉积气压增加，T_c向高温方向移动，并基于上述实验结果提出了冰 Ih (0001) 的表面相图。本文的实验结果为理解冰表面预融化的物理机制提供了重要的实空间证据，也为表面相变体系的研究提供了新的思路。

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Fig. 1.  Signatures of premelting at crystalline ice Ih (0001) surface. (a) Constant-height AFM images of a tetrahedral unit (highlighted with a yellow triangle) in Ic or Ih nanodomain (up and middle) and the corresponding structural model (bottom). (b) Constant-height AFM images of ice Ih (0001) surface grown at 121 K at 3×10^-9 mbar (up and middle) and the corresponding structural model (bottom). (c) Constant-height AFM images of ice Ih (0001) surface grown at 152 K at 3×10^-9 mbar. Individual Ic and Ih nanodomains, domain boundary, PLS and disordered regions are indicated by yellow solid lines, orange solid lines, red rectangle, red dashed ellipses and white dashed lines, respectively. (d) Zoomed-in constant-height AFM images of a typical PLS. The tip heights of (a)-(d) are -140 pm and -230 pm (a), -140 pm and -230 pm (b), -150 pm and -210 pm (c), -160 pm and -240 pm (d), respectively. The reference tip height (0 pm) corresponds to the largest tip height in the height-dependent imaging process, where the H-up water molecules can be fairly identified. (e)-(f) Structural model of a typical PLS. O atoms in the upper, lower half of the topmost bilayer, in interior bilayers and in the PLS are denoted as red, yellow, gray and purple spheres, respectively, and all H atoms are denoted as white spheres.

亮点文章

Exceptional point-induced knot structure transformations in non-Abelian braids

Lin-Sheng Bao(包淋升), Jia-Yun Ning(宁佳运), Ao-Qian Shi(史奥芊), Peng Peng(彭鹏), Zhen-Nan Wang(王瑱男), Chao Peng(彭超), Shuang-Chun Wen(文双春), and Jian-Jun Liu(刘建军)

Chin. Phys. B, 2026, Vol. 35(1): 010203

文章亮点介绍

编织与纽结之间的紧密联系为研究各类物理系统的拓扑态及相分类提供了重要视角。非厄米系统中的多带编织现象，尤其是其非阿贝尔特性，近年来受到广泛关注，但四能带系统中的非阿贝尔编织及其对应的纽结变换尚未得到系统探索。本文提出了一种非厄米四能带编织的理论模型，给出了其受跃迁调控的相位图，并建立了平庸、阿贝尔与非阿贝尔编织规则，可用编织群B4描述。研究还发现，编织过程中会出现如霍普夫链环、所罗门链环等特殊纽结结构，且这些纽结之间的变换可通过例外点实现与调控。

本文通过理论建模及可视化分析，系统展示了四能带系统中不同编织度对应的纽结结构，并揭示了例外点在纽结结构变换中的媒介作用。这不仅为理解非厄米多能带编织提供了具体的理论框架，也为拓扑光子学、类比信息处理等领域的研究提供了新思路。

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Fig. 5. Knot structure transformations and transition states. The four solid lines inside the blue dashed circle indicate the evolution of the four bands with momentum k in polar coordinates. The red dashed line indicates the starting point of the evolution of the momentum k. The evolution proceeds in the direction of the black arrow. Stages Ⅰ (t₁ = −1.0 and t₂ = −1.5) and Ⅴ (t₁ = 1.0 and t₂ = −1.5) result in a Hopf link, stage Ⅲ (t₁ = 0 and t₂ = −1.5) corresponds to a Solomon link, and stages Ⅱ (t₁ = −0.25 and t₂ = −1.5) and Ⅳ (t₁ = 0.25 and t₂ = −1.5) represent the transition states between stage Ⅰ and stage Ⅲ, and between stage Ⅲ and stage Ⅴ, respectively, both these transition states contain two EPs. Stages Ⅰ and Ⅴ experience continuous phase transitions along the peripheral blue (red) arrows in a clockwise (counterclockwise) direction.

亮点文章

Enhanced timing of a 113 km O-TWTFT link with complex maximum likelihood estimation process

Yu-Chen Fang(方宇辰), Jian-Yu Guan(管建宇), Qi Shen(沈奇), Jin-Jian Han(韩金剑), Lei Hou(侯磊), Meng-Zhe Lian(连蒙浙), Yong Wang(王勇), Wei-Yue Liu(刘蔚悦), Ji-Gang Ren(任继刚), Cheng-Zhi Peng(彭承志), Qiang Zhang(张强), Hai-Feng Jiang(姜海峰), and Jian-Wei Pan(潘建伟)

Chin. Phys. B, 2026, Vol. 35(1): 010602      

文章亮点介绍

本文作为亮点文章，聚焦于光学双向时间频率传输（O-TWTFT）技术的重大突破。随着光学时钟精度步入10^-19量级，全球高精度时间频率传输成为迫切需求，但传统卫星中继和光纤链路存在成本高、灵敏度低等局限。O-TWTFT利用光学频率梳（OFC）和线性光学采样（LOS）技术，虽具潜力，却受限于纳米瓦级的检测灵敏度，难以应对深空链路的高损耗挑战。本研究通过创新算法设计，实现了软件层面的灵敏度提升，无需硬件改动，为未来空间应用提供了低成本解决方案。

核心创新点在于提出了复数最小二乘（CLS）算法。传统方法依赖相位解缠绕，易在低信噪比下引入额外误差和错误；而CLS算法直接利用傅里叶变换后的复数频谱数据（包含振幅和相位），通过最大似然估计优化参数，避免了相位解缠绕步骤，显著提升了鲁棒性和精度。

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Fig. 1. (a) The time domain picture of O-TWTFT. The two terminals exchange frequency comb pulse trains, where their repetition rates, denoted as {fr1 and fr2, are offset by a small frequency difference Δfr. (b) The upper part of the figure presents a schematic that illustrates the optical spectra of comb 1 (in blue) and comb 2 (in red). The interference of the two combs creates a series of beat frequencies after a proper filter. The lower part of the figure depicts the CLS algorithm schematic. After the interferogram undergoes Fourier transformation and is divided by the corresponding points of the Fourier transformation of the reference interferogram, the resulting pattern theoretically forms a spiral line (parameterized by βei(kα+γ)) within the space composed of the complex plane and the frequency axis (k).

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