季伟，北京大学物理学院研究员，北京大学博雅青年学者。2014年本科毕业于吉林大学，2019年博士毕业于清华大学。毕业后先后于昆山杜克大学、清华大学和德国德国美因茨大学从事教学和研究。2025年加入北京大学物理学院。
长期从事精密磁性测量及粒子物理标准模型精确检验的研究，包括寻找标准模型之外的新相互作用及暗物质，开发极化原子磁强计及新型悬浮铁磁传感器，并推动其在粒子物理与生物医学物理等领域的应用。近年来，首次提出软磁环绕硬磁结构的自旋源设计方案被普林斯顿大学等多个国际团队采纳；首次实现超导悬浮铁磁磁强计，并超过磁测量能量分辨极限；首次实现室温磁悬浮磁强计，并实现十飞特级灵敏度，该磁强计可在地磁和常温下直接工作，大大拓展了精密测量仪器使用范围。利用超灵敏原子磁强计和高密度自旋源，对电子-电子、电子-质子及中子-中子之间的新相互作用给出迄今最严格的实验限制，对feV（10-15电子伏）能量尺度超轻轴子暗物质与中子耦合给出最强限制，并超过天文学极限。
相关研究成果发表于《美国科学院院刊》(PNAS)、《物理评论快报》（PRL）、《科学∙进展》（SA）、《自然∙通讯》（NC）等期刊；受邀为《近代物理评论》（RMP）撰写新相互作用探测方面的长篇综述。
课题组招聘博士生及博后。wei.ji@pku.edu.cn,物理学院北223
Researchgate: https://www.researchgate.net/profile/Wei-Ji-4?ev=hdr_xprf
谷歌学术链接：https://scholar.google.com/citations?user=FwovnfIAAAAJ&hl=en
Spin-dependent exotic interactions
Date:2025/08/04 Reviews of Modern Physics 92,2, 025005(2025) 自然界已知四种基本相互作用（电磁相互作用、引力相互作用、强相互作用与弱相互作用）之外，超出粒子物理标准模型的新物理效应，可能催生全新相互作用，即第五种力。本文综述聚焦于由奇异玻色子传递的自旋相关第五种力，这类玻色子包括自旋为 0 的轴子、类轴子粒子，以及自旋为 1 的 Z⁰玻色子、暗光子和类光子。诸多奇异玻色子也是解释暗物质与暗能量本质的候选粒子，其相互作用还可能违背基础对称性。各类实验已针对奇异玻色子交换所引发的费米子间自旋相关相互作用展开研究，相关探索尤其集中在低能前沿领域。本文系统介绍了搜寻奇异自旋相关相互作用所采用的实验手段与装置，包括原子共磁强计、扭秤、氮空位自旋传感器，以及高精度原子分子光谱技术。文中基于量子场论，在最简假设下推导得到一套完整的相互作用势，并采用约化耦合常数完成表征；同时汇总了目前针对奇异自旋相关相互作用的实验与天文观测约束，梳理了该领域的研究现状与未来重点发展方向。 Novel interactions beyond the four known fundamental forces in nature (electromagnetic, gravitational, strong, and weak interactions) may arise due to “new physics” beyond the standard model, manifesting as a “fifth force.” This review focuses on spin-dependent fifth forces mediated by exotic bosons such as spin-0 axions and axionlike particles and spin-1 Z' bosons, dark photons, and paraphotons. Many of these exotic bosons are candidates to explain the nature of dark matter and dark energy, and their interactions may violate fundamental symmetries. Spin-dependent interactions between fermions mediated by the exchange of exotic bosons have been investigated in a variety of experiments, particularly at the low-energy frontier. Experimental methods and tools used to search for exotic spin-dependent interactions, such as atomic comagnetometers, torsion balances, nitrogenvacancy spin sensors, and precision atomic and molecular spectroscopy, are described. A complete set of interaction potentials, derived based on quantum field theory with minimal assumptions and characterized in terms of reduced coupling constants, are presented. A summary of existing experimental and observational constraints on exotic spin-dependent interactions is given, in the process illustrating the current research landscape and promising directions of further research.
Search for a Parity-Violating Long- Range Spin-Dependent Interaction.
Date:2025/10/26 PNAS 122,41, e2512538122(2025) 高灵敏度量子传感器是探索超出标准模型相互作用的理想工具。本文展示了一种工作于共振耦合杂化自旋共振（HSR）模式的原子共磁强计，用于探测宇称破缺、时间反演守恒的相互作用。该杂化自旋共振模式可实现稳定的核 - 电子自旋耦合，在保留无自旋交换弛豫磁强计高灵敏度的同时，提升了测量带宽与系统稳定性。为降低速度调制源带来的振动噪声，我们搭建了多级隔振系统，将振动噪声抑制了 700 倍以上。针对矢量玻色子介导的宇称破缺相互作用，本研究给出了全新约束，实验灵敏度较以往结果提升三个数量级。这批新约束也为标准模型拓展方向的天体物理与实验室研究提供了有效补充。 High-sensitivity quantum sensors are a promising tool for experimental searches for beyond-Standard-Model interactions. Here, we demonstrate an atomic comagnetometer operating under a resonantly-coupled hybrid spin-resonance (HSR) regime to probe P-odd, T-even interactions. The HSR regime enables robust nuclear-electron spin coupling, enhancing measurement bandwidth and stability without compromising the high sensitivity of spin-exchange relaxation-free magnetometers. To minimize vibration-related noise from velocity-modulated sources, we implement a multistage vibration isolation system, achieving a vibration-related noise reduction exceeding 700-fold. We establish new constraints on vector-boson-mediated parity-violating interactions, improving experimental sensitivity by three orders of magnitude compared to previous limits. The new constraints complement existing astrophysical and laboratory studies of potential extensions to the Standard Model.
Constraints on Axion Mediated Dipole-Dipole Interactions.
Date:2025/10/26 Physical Review Letters 134, 18, 181801(2025) 轴子探索研究聚焦于基础物理领域几大核心难题的交叉方向，包括量子色动力学中的强 CP 问题、暗物质本质探究以及宇宙正反物质不对称性起源解析。探测轴子诱导的自旋相关相互作用，是寻找轴子的一种高效手段。但长期以来，该探测手段始终无法在轴子质量窗口范围内开展研究，核心瓶颈在于难以平衡两大需求：既要大幅抑制高极化自旋源的磁场泄漏，又要在分米级短距离内探测飞特斯拉量级的奇异物理信号。本文利用铁屏蔽型钐钴SmCo5自旋源，搭配自主设计的自补偿共磁强计，开展了轴子诱导的奇异自旋 - 自旋相互作用实验，并公布最新实验结果。通过采用复合屏蔽结构，我们实现了最高11个量级的磁场抑制效果。依托该技术，我们在轴子质量窗口内对电子 - 中子耦合强度划定了全新约束范围，相比以往实验上限提升了四个数量级；同时也给出了目前最严格的电子 - 质子耦合约束。 该研究方案不仅有望推动超越标准模型的新物理探索，还有望在生物、化学研究领域带来颠覆性应用。 The search for axions sits at the intersection of solving critical problems in fundamental physics, including the strong CP problem in QCD, uncovering the nature of dark matter, and understanding the origin of the Universe’s matter-antimatter asymmetry. The measurement of axion mediated spin-dependent interactions offers a powerful approach for axion detection. However, it has long been restricted to regions outside the “axion window” due to a significant trade-off: the need to effectively suppress the magnetic leakage from highly polarized spin sources while simultaneously detecting subfemtotesla level exotic physics signals at sub-decimeter-scale distances. In this work, we report new experimental results on axion mediated exotic spin-spin interactions using an iron-shielded SmCo5 spin source in combination with a specially designed self-compensation comagnetometer. Employing a composite shielding structure, we achieved a suppression of the magnetic field by up to 11 orders of magnitude. This enabled us to establish new constraints on the coupling between electrons and neutrons, improving previous experimental limits by up to 10 000 times within the axion window. Furthermore, we also set the strongest constraints on the coupling between electrons and protons. The proposed method holds substantial potential not only for advancing the search for new physics beyond the standard model but also for enabling transformative applications in biological and chemical research.
Dark matter search with a resonantly-coupled hybrid spin system
Date:2025/08/04 Reports on Progress in Physics 88,5,057801 (2025)。 本工作获得英国物理学会Physics World报道“A break through in the hunt for dark matter”！并入选WoS高被引期刊。 桌面型量子传感技术的最新进展，为探测暗物质的非引力相互作用提供了可行手段。传统轴子暗物质实验依赖窄带共振机制，若要覆盖较大质量区间，需耗费大量扫频时间。本文基于碱金属 - 氖 - 21 自旋体系，提出一种宽带探测方案。我们在该体系中区分出两种不同的杂化自旋耦合工作模式：低频段的自补偿模式与高频段的杂化自旋共振模式。相较于传统核磁共振技术，利用这两种模式可在保持探测灵敏度的同时，大幅拓宽氖 - 21 核自旋的测量带宽。本研究开展了针对类轴子暗物质的全域宽带搜寻，康普顿频率覆盖100~1000 Hz区间，跨度达 5 个数量级。结合暗物质随机涨落效应，我们对轴子暗物质与中子、质子的相互作用强度划定了全新约束。在 0.02~4 Hz 频率范围内，轴子 - 中子耦合强度上限降至3E-10，优于现有天体物理结果；且在 10~100 Hz 频段，该结果创下目前实验室探测的最严格约束。 Recent advances in tabletop quantum sensor technology have enabled searches for nongravitational interactions of dark matter (DM). Traditional axion DM experiments rely on sharp resonance, resulting in extensive scanning time to cover a wide mass range. In this work, we present a broadband approach in an alkali-21Ne spin system. We identify two distinct hybrid spin-coupled regimes: a self-compensation regime at low frequencies and a hybrid spin resonance regime at higher frequencies. By utilizing these two distinct regimes, we significantly enhance the bandwidth of 21Ne nuclear spin compared to conventional nuclear magnetic resonance, while maintaining competitive sensitivity. We present a comprehensive broadband search for axion-like DM, covering 5 orders of magnitude of Compton frequencies range within [100, 1000] Hz. We set new constraints on the axion DM interactions with neutrons and protons, ccounting for the effects of DM stochasticity. For the axion–neutron coupling, our results reach a low value of |gann| ⩽ 3E-10 in the frequency range [0.02, 4] Hz surpassing astrophysical limits and providing the strongest laboratory constraints in the [10, 100] Hz range.
Levitated ferromagnetic magnetometer with energy resolution well below ℏ
Date:2025/08/04 Physical Review Letters 134，18，110801（2025） 近期有研究指出了磁场测量的量子极限：即所谓能量分辨率ER ≳ ħ。该极限适用于目前绝大多数量子磁强计，包括超导量子干涉器件、固态自旋磁强计以及光泵原子磁强计。但正如单畴旋量玻色 - 爱因斯坦凝聚体的相关实验所证实，强关联自旋体系能够突破这一极限。本文研究表明，利用低温环境下悬浮于超导体上方的硬铁磁体，也可实现相近、甚至更优异的能量分辨率。实验测得能量分辨率为ER = 0.064 ħ。该成果为凝聚态物理、生物物理及基础物理领域开辟了全新应用方向。我们还据此提出一项类轴子暗物质探测实验方案，其预期探测灵敏度相较以往同类研究可提升数个数量级。 A quantum limit on the measurement of magnetic fields has been recently pointed out, stating that the socalled energy resolution ER is bounded to ER ≳ ħ. This limit indeed holds true for the vast majority of existing quantum magnetometers, including superconducting quantum interference devices and solid state spin and optically pumped atomic magnetometers. However, it can be surpassed by highly correlated spin systems, as recently demonstrated with a single-domain spinor BEC. Here, we show that similar and potentially much better resolution can be achieved with a hard ferromagnet levitated above a superconductor at cryogenic temperature. We demonstrate ER =0.064 ħ. This finding opens the way to new applications in condensed matter, biophysics, and fundamental science. In particular, we propose an experiment to search for axionlike dark matter and project a sensitivity that is orders of magnitude better than in previous searches.wei.ji@pku.edu.cn
