Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Atomically thin van der Waals crystals epitomize ideal material systems in the two-dimensional (2D) limit. This reduction in dimensionality often leads to important consequences, best exemplified by the emergence of new physics in graphene and other 2D materials that can be readily tuned by gating1,2. Vast opportunities arise in extending this top-down approach to other material systems. Recent experiments have demonstrated that the essential physics of high-temperature superconductivity in cuprates is contained within just two CuO2planes3. Here we push dimensionality reduction to the extreme by examining a single layer of Bi2Sr2CuO6+δ(Bi-2201), which comprises only one CuO2plane. In this ultimate 2D limit, we observe a robust dimensionality effect that manifests as an approximately 10% reduction in the optimal superconducting transition temperature. Moreover, this reduction in dimensionality offers unprecedented tunability—we successfully extended the phase diagram of Bi-2201 into uncharted territories via finely controlled oxygenation of single-monolayer specimens. Leveraging this tunability, we discovered that an anomalous metal state emerges between the insulating and superconducting states as the temperature approaches zero. Concurrently, we observe an anomalous scaling behaviour characterized by a divergent critical exponent. These findings illuminate the nature of the superconductor-to-insulator quantum phase transition in cuprates.
This is a preview of subscription content,access via your institution
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
Receive 52 print issues and online access
Prices may be subject to local taxes which are calculated during checkout
The datasets generated and analysed during the current study are available from the corresponding authors upon request.
We thank D.-H. Lee, X. Lin, Y. Qi, J. Wang and C. Tang for helpful discussions. We also thank H. Eisaki, G. D. Gu, A. Haug, Z. Zhang, J. Shao and Y. Zhao for their help with the experiment. Part of the sample fabrication was conducted at Nano-fabrication Laboratory at Fudan University.
H.L., Y.Y., L.M., W.R. and Y.Z. acknowledge support from National Key R&D Program of China (grant number 2022YFA1403301), Fundamental and Interdisciplinary Disciplines Breakthrough Plan of the Ministry of Education of China (grant number JYB2025XDXM120), National Science Foundation of China (grant number 12350404), Quantum Science and Technology-National Science and Technology Major Project (grant number 2024ZD0300104), and Shanghai Municipal Science and Technology Commission (grant numbers 23JC1400600 and 2019SHZDZX01). W.R. acknowledges additional support from National Science Foundation of China (grant number 12274087) Shanghai Science and Technology Development Funds (grant number 22QA1400600). Y.Y. acknowledges addtional support from Shanghai Municipal Science and Technology Project (grant number 25DZ3008100). D. Song acknowledges support from the Max Planck-UBC-UTokyo Centre for Quantum Materials and the Canada First Research Excellence Fund, Quantum Materials and Future Technologies. P.C. acknowledges support from National Key R&D Program of China (grant number 2022YFA1403102), Quantum Science and Technology-National Science and Technology Major Project (grant number 2021ZD0302502), National Science Foundation of China (grant number 12074424), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China. Y.C, L.Z. and X.Z. acknowledge support from National Science Foundation of China (grant number 11888101). Z.W. acknowledges support from National Science Foundation of China (grant number 12347107) and National Key R&D Program of China (grant number 2021YFA1402101). X.H.C. acknowledges support from the National Science Foundation of China (grant numbers 11888101 and 11534010), the National Key R&D Program of China (grant numbers 2017YFA0303001 and 2016YFA0300201), Strategic Priority Research Program of the Chinese Academy of Sciences (grant number XDB25000000) and the Key Research Program of Frontier Sciences, CAS (grant number QYZDY-SSW-SLH021). This work has been supported by the New Cornerstone Science Foundation.
Y.Z., W.R., X.H.C. and J.S. supervised the project. D. Song, R.Z., Y.C., L.Z. and X.Z. synthesized the bulk crystals. H.L., L.M. and P.C. fabricated STM devices and performed STM measurements. H.L. and Y.Y. fabricated transport devices. H.L. performed transport measurement. D. Shahar provided InOxthin films. H.L., Y.Y., Z.W., W.R. and Y.Z. analysed the data and wrote the paper with input from all authors.
Correspondence toXian Hui Chen,Wei RuanorYuanbo Zhang.