Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides

Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides | 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 Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides Maosen Qin, Dongdong Ding, Siheng Li, Xiangyan Han, Ruirui Niu, and 10 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-95219/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Electronic correlation in a flat band has been a longstanding interest because of emergent phenomena such as Mott insulator and superconductivity. Besides recent Moiré superlattice, transition metal dichalcogenides (TMDs) may directly, e.g. by forming a charge density wave in 1T-TaS 2 , reconstruct a narrow band that exhibits a correlated insulator. Here we report an emergent insulator in electron doped monolayer WSe 2 , a prototypical TMDs with direct bandgaps. By detailed mapping a cascade of phases “band insulator-superconductor-emergent insulator-metal”, we can identify, besides the superconducting dome, a narrow miniband split from the conduction band, half filling of which coincides with the insulating state. The correlation picture is supported by a density wave that possesses an isolated flat band. Finally, through evolutionary changes within the same class of materials, multivalley population is suggested to account for enhanced superconductivity and the insulator. Our finding provides new opportunities to explore correlated physics within traditionally non-correlated materials. Nanoscience Materials Theory and Modeling Electronic Materials and Devices Figures Figure 1 Figure 2 Figure 3 Figure 4 Full Text Additional Declarations There is NO Competing Interest. Supplementary Files Manuscriptsupplementaryinformation.docx Supplementary Information Cite Share Download PDF Status: Posted 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-95219","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":4403783,"identity":"b6ef5b9d-c33c-4298-b1ac-141ff3f62eae","order_by":0,"name":"Maosen Qin","email":"","orcid":"","institution":"Peking University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Maosen","middleName":"","lastName":"Qin","suffix":""},{"id":4403784,"identity":"bb302c3b-922f-47c3-b1fc-d6858d7340b6","order_by":1,"name":"Dongdong Ding","email":"","orcid":"","institution":"Peking 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Science","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Kenji","middleName":"","lastName":"Watanabe","suffix":""},{"id":4403791,"identity":"2d36e58a-6a68-4c89-8d60-8ed9a34ae48e","order_by":8,"name":"Takashi Taniguchi","email":"","orcid":"","institution":"National Institute for Materials Science, Tsukuba, Ibaraki","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Takashi","middleName":"","lastName":"Taniguchi","suffix":""},{"id":4403792,"identity":"7b1343dc-2dff-45c2-bfb9-dc2c8a0d81e2","order_by":9,"name":"Zhi-Min Liao","email":"","orcid":"https://orcid.org/0000-0001-6361-9626","institution":"Peking University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhi-Min","middleName":"","lastName":"Liao","suffix":""},{"id":4403793,"identity":"72dc5cdb-4638-4924-9a46-ef97a06babbe","order_by":10,"name":"Yuan Huang","email":"","orcid":"","institution":"Institute of Physics, Chinese Academy of 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04:10:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-95219/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-95219/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":3477964,"identity":"8ef861bf-9f65-4b0f-9c13-1d811f2761c7","added_by":"auto","created_at":"2020-11-10 00:17:43","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":244652,"visible":true,"origin":"","legend":"Observation of an emergent insulator in ionic gated monolayer WSe2. a.Schematics of an ionic liquid field effect transistor made of monolayer WSe2. The top gate (VTG) is for ionic liquid and the back gate (VBG) is for 285 nm SiO2 dielectric capacitor. b. Conductivity and Hall carrier density plotted to the left and right axes, respectively, as a function of ionic liquid gate voltages. While the conductivity tends to saturate in the hole regime, there is a significant dip on the electron side that is typically attributed to the intervalley scattering between K and Q valleys (shown in d). c-d. Valley filling for hole (c) and electron (d) doping. In the hole doped regime, only K/K’ pockets at the corners of the hexagonal Brillouin zone are occupied, whereas in the electron doped regime both K and Q valleys may be populated. Red and blue colors indicate up and down spins, respectively. e. Resistivity mapping as a function of temperature and ionic liquid gating, showing a series of electronic phases from a band insulator (BI), superconductivity (SC), an emergent insulator (EI) to a metal. Note that here the ionic liquid gating effect has been converted to the effective back gate Veff.","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1/1f726e9e1ee3d35457ab3ce5.jpg"},{"id":3477966,"identity":"317af3a9-7ff9-46e9-ad65-c3d77a158731","added_by":"auto","created_at":"2020-11-10 00:17:44","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":304324,"visible":true,"origin":"","legend":"Identification of a narrow band corresponding to the insulator. a-c.Characterization of temperature dependent resistivity across the dome-like insulating phase. In the low- (a) and high (b) density regimes, they are well fitted by Efros–Shklovskii variable range hopping, while the most insulating peak (c) could be fitted by a thermal activation model. d. The derived localization length and energy gap are plotted to the left and right axes, respectively. e. The Hall carrier density map is divided into three regions, the middle of which is highlighted by red colors for the insulating phase. The black dotted line in region 1 has a slope of Ceff=4.5 nF/cm2, which is only 1/3 of the expected capacitance. With higher gate voltages, the slope indicated by the blue dotted line restores to be normal except those close to the insulator (open symbols). The extrapolated carrier density for the insulating peak is approximately 7.3×1013 cm-2, in excellent agreement with the measured carrier density at high temperatures ~7.1×1013 cm-2 (solid circles in blue). The intercept in region 3 corresponds to a density of injected electrons ~ 1.5×1014 cm-2 (at Veff ~ 2260 V), which almost doubles that of the insulating peak. f-h. Schematics of band fillings for three regimes indexed in e including superconductivity (f), the emerging insulator (g) and the right metal (h).","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1/b89ec35d4bb396970d13ada1.jpg"},{"id":3477967,"identity":"f3faae3d-ba11-4251-9b18-7bf97e9057e3","added_by":"auto","created_at":"2020-11-10 00:17:44","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":187769,"visible":true,"origin":"","legend":"Charge density wave with a narrow band. a-b. Reconstructed (green) and original (black) Brillouin zones for the 2√3×2√3 Q-CDW (a) and the 2×1 M-CDW (b), where unreconstructed Fermi surfaces (circles and ellipses) and CDW wavevectors (arrows) are indicated. c-d. Corresponding band dispersions along high-symmetry directions. In c, the narrow band is highlighted in red. e. Formation energy of the M-CDW and Q-CDW states as a function of electron doping rates in DFT calculations.","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1/93eaa8cd99de51e5dcb64bdc.jpg"},{"id":3477968,"identity":"c865c7de-f26a-413b-9f92-72a6100ba09a","added_by":"auto","created_at":"2020-11-10 00:17:44","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":257291,"visible":true,"origin":"","legend":"Evolution of the emergent insulator and superconductivity across the semiconducting class of TMDs. a-c. Resistivity mapping as a function of temperature and gating effect for monolayer WSe2 (a), WS2 (b) and MoS2 (c), showing the similarity between the three and gradual and systematic changes due to evolving band structures. d. Summarized superconducting domes. For monolayer MoS2, no superconductivity was observed above 2 K in the present experiment. The open square is taken from Ref. 61 and the dome (dashed line) mimics the conductivity dome at high temperatures. e. The filled bars represent the energy difference between K and Q valleys obtained by both theories and experiments in the literature. Extracted values from dome peaks roughly follow the trend (see Methods, section 5).","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1/25a5e163d83d7dfe68c83451.jpg"},{"id":13553664,"identity":"0644adf9-4ff6-44fb-a5be-74c14b57cf5c","added_by":"auto","created_at":"2021-09-17 02:38:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1539508,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscriptmaintext.pdf","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1_covered.pdf"},{"id":3477969,"identity":"26c34331-7e17-4415-9c3a-93fff893f92b","added_by":"auto","created_at":"2020-11-10 00:17:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2528397,"visible":true,"origin":"","legend":"","description":"","filename":"Manuscriptmaintext.pdf","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1_stamped.pdf"},{"id":3477965,"identity":"4774229c-bbfb-4536-b980-887caffeb864","added_by":"auto","created_at":"2020-11-10 00:17:44","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":4698989,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"Manuscriptsupplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-95219/v1/4c95ba9c1754dc928a77cb81.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides","fulltext":[{"header":"Full Text","content":"\u003cp\u003eThis preprint is available for \u003ca href='/article/rs-95219/latest.pdf' target='_blank'\u003edownload as a PDF\u003c/a\u003e.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-95219/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-95219/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Electronic correlation in a flat band has been a longstanding interest because of emergent phenomena such as Mott insulator and superconductivity. Besides recent Moiré superlattice, transition metal dichalcogenides (TMDs) may directly, e.g. by forming a charge density wave in 1T-TaS\u003csub\u003e2\u003c/sub\u003e, reconstruct a narrow band that exhibits a correlated insulator. Here we report an emergent insulator in electron doped monolayer WSe\u003csub\u003e2\u003c/sub\u003e, a prototypical TMDs with direct bandgaps. By detailed mapping a cascade of phases “band insulator-superconductor-emergent insulator-metal”, we can identify, besides the superconducting dome, a narrow miniband split from the conduction band, half filling of which coincides with the insulating state. The correlation picture is supported by a density wave that possesses an isolated flat band. Finally, through evolutionary changes within the same class of materials, multivalley population is suggested to account for enhanced superconductivity and the insulator. Our finding provides new opportunities to explore correlated physics within traditionally non-correlated materials.","manuscriptTitle":"Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-11-10 00:17:41","doi":"10.21203/rs.3.rs-95219/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"629d3b3f-3c9f-40d4-91da-859399c3e681","owner":[],"postedDate":"November 10th, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":1023237,"name":"Nanoscience"},{"id":1023238,"name":"Materials Theory and Modeling"},{"id":1023239,"name":"Electronic Materials and Devices"}],"tags":[],"updatedAt":"2021-04-25T03:05:32+00:00","versionOfRecord":[],"versionCreatedAt":"2020-11-10 00:17:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-95219","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-95219","identity":"rs-95219","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}