物理与天文学院蒋庆东教授课题组和合作团队首次实现真空涨落对超导的增强效应

近日，上海交通大学物理与天文学院、李政道研究所蒋庆东教授带领的理论团队与中国科学技术大学曾长淦教授、程广珲教授带领的实验团队，以及同时任职于上海交通大学李政道研究所和美国麻省理工学院的Frank Wilczek教授（2004年诺贝尔物理学奖得主）合作，首次实现了暗腔真空涨落对超导增强效应。实验研究由中国科学技术大学团队主导，理论建模与机制阐释由上海交通大学团队主导完成。相关成果以“Evidence for vacuum-enhanced superconductivity in NbSe₂”为题，于8月19日以加速文章预览（Accelerated Article Preview）形式发表于《自然》。

真空并非真正意义上的“空无一物”，在量子电动力学的世界里，根据海森堡不确定原理，其基态具有不可消除的零点能，伴随着虚粒子的不断产生与湮灭。因此，真空空间可被视为充满真空涨落的动态“海洋”。 兰姆移位、自发辐射、卡西米尔效应等一系列重要物理效应，本质上皆源于真空量子涨落。

然而自由空间中的真空涨落强度通常较弱，很难对宏观凝聚态物质产生可观测效应。为此，研究团队引入太赫兹分裂环谐振器构成的“暗腔”，无需外部驱动，通过重塑电磁环境，可显著增强真空涨落。研究团队将超导体NbSe₂嵌入太赫兹暗腔，构建超导体-暗腔耦合器件（图b）。通过系统对比腔外与腔内超导体特性，研究团队发现，NbSe₂的超导临界温度获得实质性提高（图c）。在六层NbSe₂器件中观测到超导临界温度的提升达到5.4%。与此同时，超导体的临界电流和临界磁场在超导转变附近显著增强。这项工作是真空涨落增强超导的首次实验观测。

图: (a) 真空涨落增强超导示意图；(b) 超导体-暗腔耦合器件示意图；(c) 腔外与腔内超导电输运结果对比；(d) 超导增强系数对暗腔特征频率的依赖关系；(e) 超导态与暗腔交换虚光子的费曼图。

为厘清超导增强来源，团队围绕腔体几何结构和特征频率、材料厚度、介电材料和金属条带等多个维度，开展了系统而严格的对照实验，有效排除了应变、材料退化、非均匀性以及金属屏蔽效应等常规因素的影响。特别是，实验发现超导增强效应随暗腔特征频率呈现共振峰形依赖关系（图d），这一与腔体光子学特征紧密相关的结果，为超导态与暗腔模式之间的耦合提供了有力的实验证据。

蒋庆东教授研究组（包括蒋庆东教授，Gabriel Cardoso 博士，杨柳博士以及朱雨非博士）与Frank Wilczek教授共同承担了本工作的理论建模与机制阐释。基于Ginzburg-Landau理论框架，他们提出，超导态与暗腔交换虚光子，降低超导态能量，从而增强超导（图e）。当腔模的特征能量（由腔体特征频率决定）与超导材料的低能涨落能量相匹配时，系统表现出共振增强，即图d展示的超导增强效应达到峰值。

该研究利用腔体工程化真空涨落，实现了对超导稳态的无外部驱动、非接触式的增强。不同于电接触栅压或光泵浦等手段，该方法通过超导体与暗腔真空场耦合，改变超导态能量进而提升超导性，为量子材料研究提供了一种新的“非接触式旋钮”。这一工作不仅为探索超导机理与设计超导器件带来新思路，也展现出真空涨落工程应用于更多量子物态的潜力。近年来，蒋庆东教授团队持续开展真空调控物态的理论研究 (PRL 131, 223601 (2023); PRL 132, 166901 (2024); PRL 135, 236901 (2025))，并提出通过工程化真空环境调控电子与光子行为的“真空电子学”（vacuumronics）研究构想 (npj Nanophotonics 2, 46 (2025))。与此同时，曾长淦教授团队前期曾实现磁场驱动下卡西米尔力由吸引到排斥的可逆转变（Nat. Phys. 20, 1282–1287 (2024)）。双方的研究积累共同推动了真空物态调控向超导体系的拓展。

中国科学技术大学博士生王哲研为论文第一作者。曾长淦教授、程广珲教授、蒋庆东教授和Frank Wilczek教授为论文共同通讯作者。该研究得到国家自然科学基金委员会、合肥国家实验室、上海市、上海交通大学及相关合作单位的支持。

SJTU and USTC Teams Report First Experimental Evidence for Vacuum-Enhanced Superconductivity

A research team led by Prof. Qingdong Jiang at the School of Physics and Astronomy，Tsung-Dao Lee Institute, Shanghai Jiao Tong University (SJTU), has collaborated with the experimental team led by Profs. Changgan Zeng and Guanghui Cheng at the University of Science and Technology of China (USTC), as well as Prof. Frank Wilczek—a 2004 Nobel Laureate in Physics who holds appointments at both TDLI and the Massachusetts Institute of Technology—to obtain the first experimental evidence that dark-cavity vacuum fluctuations can enhance superconductivity.

The experimental work was led by the USTC team, while the theoretical modeling and interpretation of the underlying mechanism were led by the SJTU team. The study, titled “Evidence for vacuum-enhanced superconductivity in NbSe_2,” was published in Nature on August 19 as an Accelerated Article Preview.

The quantum vacuum is not truly empty. Even in its ground state, the electromagnetic field exhibits irreducible zero-point fluctuations, whose physical consequences include the Lamb shift, spontaneous emission, and the Casimir effect. In free space, however, these fluctuations are generally too weak to appreciably modify macroscopic quantum states. A central challenge in condensed-matter physics and cavity quantum electrodynamics is therefore to amplify and harness vacuum fluctuations through engineered electromagnetic environments.

In this study, the researchers constructed an undriven “dark cavity” using terahertz split-ring resonators. By reshaping the local electromagnetic environment, the cavity enhances vacuum fluctuations without external illumination. NbSe₂ was embedded in the cavity to form a coupled superconductor–dark-cavity device. Comparisons between samples inside and outside the cavity showed that the superconducting transition temperature of six-layer NbSe₂ increased by as much as 5.4%. The critical current and critical magnetic field were also substantially enhanced near the superconducting transition.

To establish the origin of the effect, the experimental teams systematically varied the cavity geometry, characteristic frequency, and dielectric environment. These control experiments ruled out conventional explanations such as strain, sample inhomogeneity, and metallic screening. Most importantly, the superconductivity enhancement displayed a pronounced resonant peak as a function of the dark-cavity frequency. This frequency-selective response provides key evidence that the enhancement originates from coupling between the superconducting state and the vacuum modes of the cavity.

Figure: (a) Schematic of the coupled superconductor–dark-cavity device; (b) comparison of superconducting transport inside and outside the cavity; (c) dependence of the superconductivity-enhancement factor on the characteristic dark-cavity frequency; and (d) Feynman diagram of virtual-photon exchange between the superconducting state and the dark cavity.

To explain the observations, the theoretical team developed a coupled superconductor–vacuum-field framework based on Ginzburg–Landau theory and cavity quantum electrodynamics, explicitly incorporating the spatially nonuniform modes of the dark cavity. The theory shows that virtual-photon exchange with the cavity can renormalize the superconducting free energy and thereby stabilize the superconducting state. When the characteristic energy of the cavity mode matches the low-energy fluctuation scale of the superconductor, the virtual-photon exchange is resonantly enhanced, producing a maximum enhancement at a specific cavity frequency. The model accounts for the observed resonant response and identifies both the cavity frequency and its spatial mode profile as key control parameters.

The study provides the first experimental evidence that engineered vacuum fluctuations can enhance superconductivity. Unlike electrical contacts, gate voltages, or optical pumping, this approach controls a quantum material by modifying its surrounding vacuum electromagnetic environment, offering a new noncontact control knob that requires no external drive.

In recent years, Prof. Jiang’s group has pursued a broader theoretical interest on controlling states of matter through the quantum vacuum. The group introduced the concept of “vacuumronics”（npj Nanophotonics 2, 46 (2025)），in which engineered vacuum environments are used to manipulate electronic and photonic behavior (PRL 131, 223601 (2023); PRL 132, 166901 (2024); PRL 135, 236901 (2025)). In parallel, Prof. Zeng’s team previously demonstrated a magnetic-field-driven reversal of the Casimir force from attraction to repulsion (Nature Physics 20, 1282–1287 (2024)). The present study brings these complementary research directions together and extends vacuum-state engineering to superconductivity.

Zheyan Wang, a doctoral student at USTC, is the first author of the paper. Profs. Changgan Zeng, Guanghui Cheng, Qingdong Jiang, and Frank Wilczek are the corresponding authors. The research was supported by the National Natural Science Foundation of China, Hefei National Laboratory, the Shanghai Municipality, Shanghai Jiao Tong University, and other participating institutions.

作者： 上海交大物理与天文学院 供稿单位： 物理与天文学院