成果发布 | 解锁奇异物态的简单“盒子”：利用真空涨落诱导手性自旋液体
TDLI RESEARCH ACHIEVEMENTS
如何让固体“熔化”？日常经验给出的答案很简单——加热。加热会增强热涨落，使原本整齐排列的原子被“摇动”离开平衡位置，从而驱动固体向液体转变。然而，自然界还存在另一种更为精妙的涨落：量子涨落。即使在绝对零度，它们依然存在，并同样能够让固体失去刚性。一个典型例子是液态氦，它在绝对零度下仍保持液态，正是由于其量子涨落异常强烈。
在最近发表于 Physical Review Letters的一项研究中，来自开云网页登录 李政道研究所的青年学者蒋庆东副教授团队提出了一种全新的方式来利用真空量子涨落。他们的研究表明，只需将 Kagome 晶格置入一种特殊设计的光学腔体之中，经过腔体修饰的真空涨落便能自发稳定一种罕见的拓扑量子液体——手性自旋液体。
探索手性自旋液体（CSL）
手性自旋液体（Chiral Spin Liquids，CSLs）是一类独特的物质形态，因其具备长程纠缠、拓扑序及分数量子激发等特性，数十年来始终吸引着凝聚态物理学家的目光。由于其在拓扑量子计算中的潜在应用，手性自旋液体被视为凝聚态物理长期追寻的重要目标。然而，尽管进行了大量理论与实验探索，手性自旋液体的存在性依然悬而未决。核心难题集中在两个基本问题上：
如何在热平衡条件下，通过可控的外部调节机制稳定地产生手性自旋液体？
如果这种有序相确实存在，又该如何在超越热霍尔效应这一微弱的信号之外，找到明确的证据？
解决方案：给量子材料加个“盒子”
在这项最新研究中，团队提出了一个出乎意料地简单而有效的方案：将材料置于一种特殊的“量子盒子”——旋光光学腔体中。这个腔体不仅仅是容纳材料的容器，它更从根本上改变了周围真空的性质。就像把一个共振物体放入盒子里会改变其振动方式一样，腔体的边界会重新塑造充斥在空间中的真空量子涨落（虚光子）。
研究人员展示，只需将 Kagome 晶格限制在这一光学腔体中，经腔体修饰的真空涨落便会自发与电子自旋发生耦合，从而稳定难以探测的手性自旋液体。这一方法将实现奇异量子相的难题，转化为几何结构的设计问题。更重要的是，它依赖的是腔体内部真空的内禀性质，而非需要持续施加、容易引入额外加热的外部驱动，从而更有利于保持体系的量子有序。
一种“非侵入式”的方式看见量子相：
不仅如此，该研究还提出了另一个关键难题的解决方案：如何在不破坏体系的前提下探测手性自旋液体。研究团队发现，腔体内部的光场动力学本身就是一种非侵入式探测手段。他们的研究表明，实验可观测的物理量 —— 例如平均光子数、以及与该系统耦合的波导的输运特性 —— 能够揭示手性自旋液体的存在。由此，电子体系中隐蔽的量子有序与可测量的光学行为之间建立起了直接联系。
研究意义：
本工作为基于微腔真空的量子材料调控开辟了新的方向，指出只需改变材料周围的电磁环境，就能“调节”真空本身，从而设计所需的拓扑量子相。这一发现为未来在超冷原子晶格以及阻错磁性材料（如 Herbertsmithite）中的实验提供了全新的理论方案。
本研究的主要推动力量来自第一作者魏晨岸博士（麻省大学阿默斯特分校 /A. Alikhanyan 国家科学实验室）。杨柳博士（李政道研究所博士后）作为第二作者，为研究的推进也作出了十分重要的贡献。蒋庆东教授担任通讯作者，设计了该项研究的整体思路和研究方向。
论文原文
https://journals.aps.org/prl/abstract/10.1103/8qx2-xxh2
致谢
本研究得到以下项目的支持：科技创新2030计划（编号 2021ZD0301900）、国家自然科学基金（编号 12374332）、上海市量子开云足球app官方下载安装 中心培育项目（编号 LZPY2024），以及上海市科技创新行动计划（编号 24LZ1400800）。魏晨岸博士同时部分获得亚美尼亚共和国科学教育委员会（MESCS RA）高教与科学委员会（科研项目编号 25PostDoc1C003）的资助。
Unlocking Exotic Matter with a Simple “Box”: How Vacuum Fluctuations Create Chiral Spin Liquids
TDLI RESEARCH ACHIEVEMENTS
How do you melt a solid? The everyday answer is simple—heat it. Heating increases thermal fluctuations, shaking atoms out of their orderly arrangement and driving the transition from solid to liquid. But nature hosts another, more subtle kind of fluctuation: quantum fluctuations. These persist even at absolute zero and can also melt a solid. A striking example is liquid helium, which remains fluid at zero temperature precisely because its quantum fluctuations are so strong.
In a new study published in Physical Review Letters, a research team led by tenure-track fellow, associate professor Qing-Dong Jiang from Tsung-Dao Lee Institute, Shanghai Jiao Tong University presents a fundamentally new way to harness these vacuum quantum fluctuations. Their work demonstrates that simply placing a Kagome lattice inside a specially designed optical cavity can stabilize an exotic topological quantum liquid—the elusive chiral spin liquid.
The Quest for Chiral Spin Liquids:
Chiral Spin Liquids (CSLs) are a unique state of matter that have captivated physicists for decades. Characterized by long-range entanglement, topological order, and fractional excitations, CSLs are considered a long-sought state in condensed matter physics due to their potential applications in robust topological quantum computing. Despite extensive theoretical and experimental efforts, the very existence of chiral spin liquids remains unresolved. This challenge centers on two fundamental questions:
How can a chiral spin liquid be reliably realized using an external tuning mechanism under equilibrium conditions?
If such an order exists, how can it be unambiguously identified—beyond the often subtle and elusive thermal Hall effect?
The Solution: Just add a "Box" to create it
In this new study, the research team proposes a simple solution: place the material inside a specific type of Quantum Box—a gyrotropic optical cavity. This cavity does more than merely contain the material; it fundamentally alters the vacuum environment itself. Just as placing a resonant object inside a box changes how it vibrates, the cavity boundaries reshape the vacuum quantum fluctuations (virtual photons) that permeate space.
The researchers demonstrate that by simply confining a Kagome lattice within this cavity, the modified vacuum fluctuations spontaneously interact with electron spins and stabilize the elusive chiral spin liquid state. This approach transforms the challenge of creating exotic phases into a problem of structural geometry. Importantly, it relies on the intrinsic properties of the vacuum inside the cavity rather than on active external driving, which may introduce heating effects that are not ideal for maintaining quantum order.
A Non-Invasive Way to "See" Quantum Phases
Beyond creating the phase, the paper also offers a solution to another major challenge: how to detect it without disturbing it. The researchers identified that the light dynamics within the cavity serve as a non-invasive probe. They showed that experimentally accessible observables—such as the average photon number and the transport properties of a waveguide coupled to the system—can reveal the presence of the chiral spin liquid. This establishes a direct link between the hidden quantum order of electrons and the measurable behavior of light.
Research Impact
This work opens a new avenue for cavity engineering of quantum materials, suggesting that the vacuum itself can be tuned—simply by changing the electromagnetic environment around a material—to design topological phases. The findings provide a theoretical foundation for future experiments in ultracold atomic lattices and frustrated magnetic materials like Herbertsmithite.
The study was driven primarily by the efforts of first author Dr. Chenan Wei (University of Massachusetts Amherst /A. Alikhanyan National Science Laboratory). Dr. Liu Yang, a postdoctoral fellow at the Tsung-Dao Lee Institute, made very important contributions as the second author. Prof. Qing-Dong Jiang served as the corresponding author and guided the overall direction of the work.
Article Link
https://journals.aps.org/prl/abstract/10.1103/8qx2-xxh2
Acknowledgement
This work was supported by the Innovation Program for Quantum Science and Technology Grant No. 2021ZD0301900, the National Natural Science Foundation of China (NSFC) under Grant No. 12374332, the Cultivation Project of Shanghai Research Center for Quantum Sciences Grant No. LZPY2024, and the Shanghai Science and Technology Innovation Action Plan Grant No. 24LZ1400800. C. W. was partially supported by the Higher Education and Science Committee of MESCS RA (Research Project No. 25PostDoc1C003).
文稿 | 蒋庆东
编辑 | 孟闻卓
责任编辑 | 李姝姝 陆梦珠