{"paper_id":"39ae3364-b4ca-41ae-a7ec-10a838b0a228","body_text":"Anomalous enhancement of charge density wave in kagome superconductor CsV3Sb5 approaching the 2D limit | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Anomalous enhancement of charge density wave in kagome superconductor CsV3Sb5 approaching the 2D limit Boqing Song, Tianping Ying, Xianxin Wu, Wei Xia, Qiangwei Yin, and 11 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2130263/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 29 Apr, 2023 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract The two-dimensional (2D) kagome lattice is a versatile platform to explore exotic quantum states. The recently discovered kagome superconductors AV3Sb5 (A= Cs, Rb, K) containing vanadium kagome lattices exhibit a variety of intriguing phenomena, such as a charge density wave (CDW) with time-reversal symmetry breaking and possible unconventional superconductivity. In particular, in bulk samples the CDW displays a three-dimensional character and tends to be suppressed by external or chemical pressure. However, the characteristics and stability of the CDW order in atomically thin flakes approaching the 2D limit remain unexplored. Here, through combined electrical transport, scanning transmission electron microscopy (STEM) and Raman scattering measurements, we report an intertwined-order phase diagram of CsV3Sb5 flakes down to the monolayer. After successfully confirming the stability of the kagome lattice down to at least 4 layers, we observe a non-monotonic evolution of the CDW transition temperature TCDW with a reduction of flake thickness. TCDW first decreases to a minimum value of 72 K at 27 layers and then increases abruptly, reaching a record-high value of 120 K at 5 layers. The superconducting transition temperature (Tc) features an inverse variation with TCDW. Flakes with less than 5 layers, however, become more insulating with decreasing thickness. Raman scattering measurements reveal a weakened electron-phonon coupling with the reduction of sample thickness, suggesting that a crossover from electron-phonon coupling to dominantly electronic interactions could account for the non-monotonic thickness dependence of TCDW. Our work demonstrates the novel effects of dimension reduction and carrier doping on quantum states in thin flakes and provides crucial insights into the complex mechanism of the CDW order in the family of AV3Sb5 kagome metals. Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformation.pdf Cite Share Download PDF Status: Published Journal Publication published 29 Apr, 2023 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-2130263\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":143397893,\"identity\":\"d8505ba1-ff6f-4faf-aaaa-792574b11a5e\",\"order_by\":0,\"name\":\"Boqing Song\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Fudan University\",\"correspondingAuthor\":false,\"submittingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Boqing\",\"middleName\":\"\",\"lastName\":\"Song\",\"suffix\":\"\"},{\"id\":143397894,\"identity\":\"959f1e35-aa64-4c97-a256-18107d9eb0b5\",\"order_by\":1,\"name\":\"Tianping 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100190\",\"correspondingAuthor\":false,\"submittingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Xiaolong\",\"middleName\":\"\",\"lastName\":\"Chen\",\"suffix\":\"\"},{\"id\":143397904,\"identity\":\"6838ce76-b724-49b1-ad21-8976c4a1bf62\",\"order_by\":11,\"name\":\"Jiangping Hu\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0002-4837-7742\",\"institution\":\"Institute of Physics\",\"correspondingAuthor\":false,\"submittingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Jiangping\",\"middleName\":\"\",\"lastName\":\"Hu\",\"suffix\":\"\"},{\"id\":143397905,\"identity\":\"7722090c-f4a2-468d-8513-1128792ae457\",\"order_by\":12,\"name\":\"Andreas Schnyder\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0002-1029-815X\",\"institution\":\"Max Planck Institute for Solid State Research\",\"correspondingAuthor\":false,\"submittingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Andreas\",\"middleName\":\"\",\"lastName\":\"Schnyder\",\"suffix\":\"\"},{\"id\":143397906,\"identity\":\"554a4397-5346-431b-96fa-57b4837b955c\",\"order_by\":13,\"name\":\"Hechang Lei\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-0850-8514\",\"institution\":\"Renmin University of China\",\"correspondingAuthor\":false,\"submittingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Hechang\",\"middleName\":\"\",\"lastName\":\"Lei\",\"suffix\":\"\"},{\"id\":143397907,\"identity\":\"1daa1f17-4f55-4b5f-ad3e-2fe1c1c8e8c5\",\"order_by\":14,\"name\":\"Yanfeng Guo\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0002-9386-4857\",\"institution\":\"ShanghaiTech 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The recently discovered kagome superconductors AV3Sb5 (A= Cs, Rb, K) containing vanadium kagome lattices exhibit a variety of intriguing phenomena, such as a charge density wave (CDW) with time-reversal symmetry breaking and possible unconventional superconductivity. In particular, in bulk samples the CDW displays a three-dimensional character and tends to be suppressed by external or chemical pressure. However, the characteristics and stability of the CDW order in atomically thin flakes approaching the 2D limit remain unexplored. Here, through combined electrical transport, scanning transmission electron microscopy (STEM) and Raman scattering measurements, we report an intertwined-order phase diagram of CsV3Sb5 flakes down to the monolayer. After successfully confirming the stability of the kagome lattice down to at least 4 layers, we observe a non-monotonic evolution of the CDW transition temperature TCDW with a reduction of flake thickness. TCDW first decreases to a minimum value of 72 K at 27 layers and then increases abruptly, reaching a record-high value of 120 K at 5 layers. The superconducting transition temperature (Tc) features an inverse variation with TCDW. Flakes with less than 5 layers, however, become more insulating with decreasing thickness. Raman scattering measurements reveal a weakened electron-phonon coupling with the reduction of sample thickness, suggesting that a crossover from electron-phonon coupling to dominantly electronic interactions could account for the non-monotonic thickness dependence of TCDW. 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