Observation of dissipationless fractional Chern insulator

Nature Physics (2026)Cite this article The fractional quantum anomalous Hall effect has recently been experimentally observed in fractional Chern insulators at zero magnetic field. However, an outstanding challenge is the presence of substantial longitudinal resistance, even though the anomalous Hall resistance is quantized. This dissipation is probably linked to imperfect sample quality. Here we demonstrate a twisted MoTe2 bilayer device that exhibits quantized anomalous Hall resistance and vanishing longitudinal resistance for the fractional state, such that it is a dissipationless fractional Chern insulator. Unlike fractional quantum Hall states, where the energy gap increases with magnetic field, the thermal activation gap of the fractional state decreases rapidly with magnetic field and then plateaus above a few teslas. This behaviour reflects the coexistence of two distinct excitation channels: spinful quasiparticles dominate transport at low magnetic fields whereas spinless quasiparticles govern transport at high fields, where Zeeman splitting suppresses spin-flip processes. Our results provide insights into the energy scale of fractional Chern insulators and indicate a pathway to the quantum engineering of exotic correlated topological states.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 $32.99 / 30 days cancel any timeSubscribe to this journal Receive 12 print issues and online access $259.00 per yearonly $21.58 per issueBuy this articleUSD 39.95Prices may be subject to local taxes which are calculated during checkoutThe raw datasets underlying the colour plots are large and are available from the corresponding author upon reasonable request. Source data are provided with this paper.Neupert, T., Santos, L., Chamon, C. & Mudry, C. Fractional quantum Hall states at zero magnetic field. Phys. Rev. Lett. 106, 236804 (2011).Article ADS Google Scholar Sheng, D., Gu, Z.-C., Sun, K. & Sheng, L. Fractional quantum Hall effect in the absence of Landau levels. Nat. Commun. 2, 389 (2011).Article ADS Google Scholar Regnault, N. & Bernevig, B. A. Fractional Chern insulator. Phys. Rev. X 1, 021014 (2011).

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The Flatiron Institute is a division of the Simons Foundation.Department of Physics, University of Washington, Seattle, WA, USAHeonjoon Park, Weijie Li, Chaowei Hu, Christiano Beach, David Cobden, Jiun-Haw Chu, Di Xiao & Xiaodong XuDepartment of Physics, Princeton University, Princeton, NJ, USAMiguel Gonçalves, Juan Felipe Mendez-Valderrama, Jonah Herzog-Arbeitman, B. Andrei Bernevig & Nicolas RegnaultResearch Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, JapanTakashi TaniguchiResearch Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba, JapanKenji WatanabeDepartment of Physics, Massachusetts Institute of Technology, Cambridge, MA, USALiang FuDonostia International Physics Center, Donostia/San Sebastian, SpainB. Andrei BernevigIKERBASQUE, Basque Foundation for Science, Bilbao, SpainB. Andrei BernevigCenter for Computational Quantum Physics, Flatiron Institute, New York, NY, USANicolas RegnaultLaboratoire de Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, FranceNicolas RegnaultDepartment of Materials Science and Engineering, University of Washington, Seattle, WA, USADi Xiao & Xiaodong XuSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarSearch author on:PubMed Google ScholarX.X. conceived and supervised the project. H.P. fabricated the samples and performed the transport measurements. W.L. performed the RMCD measurements with support from C.B. H.P., D.C., L.F., B.A.B., N.R., D.X. and X.X. analysed and interpreted the results. M.G., J.F.M.-V., J.H.-A., D.X., B.A.B. and N.R. performed the magnetic-field-dependent gap analysis. T.T. and K.W. synthesized the hBN crystals. C.H. and J.-H.C. grew and characterized the bulk MoTe2 crystals. H.P., D.X. and X.X. wrote the paper with input from all authors. All authors discussed the results.Correspondence to Xiaodong Xu.The authors declare no competing interests.Nature Physics thanks Rafael Luque Merino and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.a, Schematic of horizontal flux transport growth of MoTe2 crystal in Te flux under temperature gradient from T1 = 600 °C to T2 = 550 °C. b, 200 × 200 nm2 conductive atomic force microscopy (c-AFM) image taken on exfoliated bulk commercial crystals under Vbias = 1.3 V showing several types of defects with the total concentration on the order of 1011 cm−2. The exact defect types are not known. c, 500\(\times\)500 nm2 c-AFM image taken on exfoliated bulk crystals grown by horizontal flux transport (see Methods). The applied Vbias = 0.9 V. A single type of defects is highlighted in blue circles with density of 2 × 109 cm−2. d, 200 × 200 nm2 c-AFM image taken within the orange box in c.a-d, Each row displays, from top to bottom, the device schematic, optical image, and atomic force microscopy (AFM) image. a, Bottom gate structure featuring pre-patterned platinum (Pt) electrodes on an hBN/graphite stack. b, Placement of the hBN/tMoTe2 stack onto the bottom gate. Inset: Optical image of a monolayer MoTe2 flake bisected using an AFM tip. c, Patterning of Pt contact gates on top of each Pt electrode. d, Transfer of the top gate structure (hBN/graphite/hBN) onto the device. e, Contact-mode AFM images taken after hBN/tMoTe2 transfer in b, illustrating the progressive removal of bubbles outside the Hall bar region. Scale bars: 5 μm (optical images), 2 μm (AFM images).a, AFM image after Pt contact-gate (CG) deposition. Scale bar: 1 µm. b, c, Cross-sectional schematics (top) and energy diagrams (bottom) of the contact region without (b) and with (c) a contact gate. Contact between Pt and the TMD induces strong charge transfer, resulting in a “metallized” TMD. Strain and disorder at the 1D interface between this region and the intrinsic channel create localized in-gap states that form a Schottky barrier. A large negative CG voltage introduces a fringe field that gradually dopes these interface states, reducing the barrier height.d, Misaligned CG layout that covers only one side of the contact, leaving a Schottky barrier on the opposite side. This design blocks hole transport through single-gated or monolayer regions, suppressing parasitic conduction. The bulb-shaped contact gate end ensures current flows only within the Hall-bar channel. e, f, Four-terminal (Rxx, e) and two-terminal (R2T, f) resistances versus dual-gate voltages for the device in the main text, measured at 4 K. g-i, In contrast, devices where the CG fully overlaps the contact exhibit parallel conduction channels (g) and corresponding features in Rxx (h) and R2T (i) aligned with a single gate (black arrows), including abrupt drops in R2T at large negative top-gate voltages. The absence of such features in the main device confirms effective suppression of parallel conduction by the misaligned CG design.a, Longitudinal (Rxx) resistance as a function of filling factor (ν) and electric field (D/ε0) at 10 mK. b, Linecut of Rxx as a function of filling factor at D/ε0 = 25 mV/nm. The Rxx is symmetrized at |µ0H | = ±0 mT by initializing the device at ±0.2 T and sweeping down the magnetic field to zero. The observed phase diagram is the same as the one shown in Fig. 1c, except small fluctuations in Rxx due to spin fluctuations during carrier density sweeps. c, Rxx and d, -Rxy as a function of magnetic field (µ0H) and filling factor (ν). Data is symmetrized and antisymmetrized, respectively. e, Linecuts of Rxx at various magnetic fields. The peak position of ν = -3/2 does not disperse, indicative of a topologically trivial charge-ordered state.Source dataa-b, Longitudinal resistance Rxx (a) and Hall resistance -Rxy (b) as functions of electric field D/ε0 at various filling factors (ν), symmetrized and antisymmetrized, respectively at µ0H = ±200mT. Near but below ν = -1, the system remains in a quantum anomalous Hall state even at finite D/ε0 ≈ 75 mV/nm, with vanishing Rxx and quantized -Rxy ≈ h/e2. As the filling increases, the system transitions into a ferromagnetic metal near D/ε0 ≈ 0, and a nonmagnetic metal at larger |D/ε0 | . c-d, Temperature-dependent Rxx versus D/ε0 at ν = -2/3 (c) and ν = -3/5 (d). At low electric fields, Rxx vanishes, indicating an incompressible FCI state. Increasing D/ε0 drives a sharp transition to a charge-ordered insulator, followed by metallic behavior at higher fields. e-f, Arrhenius fits of Rxx at ν = -2/3 (e) and ν = -3/5 (f) used to extract the energy gaps of the charge-ordered insulating states, assuming Rxx ~ R0 exp(-Δ/2kBT), where Δ is the energy gap. g, Extracted gaps Δ as a function of D/ε0 for both fillings. Across the charge-ordered regime, the ν = -3/5 state consistently exhibits smaller gaps than ν = -2/3. Error bars indicate uncertainty in the fitted activation gap Δ from Arrhenius fits, with data points representing best-fit values. Data are from a single twisted MoTe2 bilayer device (n = 1). No biological or technical replicates or control groups were used.Source dataa, Symmetrized Rxx and antisymmetrized -Rxy at µ0H = ± 150 mT for the -2/3 FCI state. Rxx ≈ -Rxy around a temperature of 5 K. b, c, and d, similar measurements as (a) for the -3/5, -4/7, and -5/9 FCI state. e, Arrhenius plot of Rxx for the -2/3, -3/5, -4/7, and -5/9. The extracted thermal activation gap is shown in the inset for the -2/3 and -3/5 state, where the line is a guide to the eye for the expected scaling behavior for the fractional quantum Hall states as a reference. Error bars indicate uncertainty in the fitted activation gap Δ from Arrhenius fits, with data points representing best-fit values. Data are from a single twisted MoTe2 bilayer device (n = 1). No biological or technical replicates or control groups were used.Source dataFor each panel, the corresponding magnetic field is marked on the top.RMCD as a function of ν and D/ε0 at different temperatures (T), measured at a small field of 5 mT. The ferromagnetic signal at ν = -2/3 disappears around 4-5 K while the ν = -1 signal persists up to approximately 13-14 K, consistent with the temperature dependence of Rxy.a, RMCD as a function of filling (ν) and temperature (T) for the device discussed in the main text, measured at a small magnetic field of 30mT and electric field D/ε0 = 0. b, Linecut of RMCD vs ν at T = 1.6 K, which shows a monotonic decrease from ν = -1 to -2/3. c-f, (top) The hysteretic component of RMCD (ΔRMCD) as a function of magnetic field and temperature for the Jain sequence fractional fillings ν = -2/3, -3/5, -4/7, -5/9, respectively. (bottom) Linecuts at different temperatures extracted from the colorplot. The Curie temperature decreases at higher order filling factors.Source dataa, Raw data for the longitudinal resistance Rxx at different temperatures and magnetic fields, together with an example fit (solid line) to Eq.3 by selecting the data for \(0.15{{\rm{K}}}^{-1} < {T}^{-1} < 0.35{{\rm{K}}}^{-1}\) and \({R}_{{\rm{xx}}} < 7.5{\rm{k}}\Omega\). The different magnetic fields are color-coded according to the legend. The extracted fitted parameters are \({\varDelta }_{{FCI}}=19.9\pm 0.3{\rm{K}}\), \({\varDelta }_{S}^{0}=55\pm 2{\rm{K}}\), \({g}^{* }=19.3\pm 0.8\) and \(\alpha =(4\pm 1)\times {10}^{-3}\). b-d, Best-fit parameters for different choices of data selection. These include different choices of truncation ranging from \(0.1{{\rm{K}}}^{-1} < {T}_{\max }^{-1} < 0.2{{\rm{K}}}^{-1}\) (always considering \({T}^{-1} < 0.35{{\rm{K}}}^{-1}\)) and \(5{\rm{k}}\Omega < {R}_{{\rm{xx}}}^{\max } < 10{\rm{k}}\Omega\), where \({T}_{\max }\) and \({R}_{{\rm{xx}}}^{\max }\) are respectively the maximum considered temperatures and resistances. We also tested the impact of fitting with larger weight in the small \(B\) data, where the most notable variations occur. We used different weighting functions \(f(B)=({({B}_{\max }-B)/{B}_{\max })}^{\eta }\), with \(\eta =\mathrm{0,1,2}\) indicated by the different colors of the data points in the figure, and \({B}_{\max }=8{\rm{T}}\). Error bars indicate uncertainty in the fitted parameters, with data points representing best-fit values. Data are from a single twisted MoTe2 bilayer device (n = 1). No biological or technical replicates or control groups were used.Statistical data for Fig. 2.Statistical data for Fig. 3.Statistical data for Fig. 4.Statistical data for Extended Data Fig. 4.Statistical data for Extended Data Fig. 5.Statistical data for Extended Data Fig. 6.Statistical data for Extended Data Fig. 9.Statistical data for Extended Data Fig. 10.Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.Reprints and permissionsPark, H., Li, W., Hu, C. et al. Observation of dissipationless fractional Chern insulator. Nat. Phys. (2026). https://doi.org/10.1038/s41567-025-03167-2Download citationReceived: 10 March 2025Accepted: 31 December 2025Published: 30 January 2026Version of record: 30 January 2026DOI: https://doi.org/10.1038/s41567-025-03167-2Anyone you share the following link with will be able to read this content:Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative