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Jing Ding, Hanxiao Xiang, Jiannan Hua, Wenqiang Zhou, Naitian Liu, Le Zhang, Na Xin, Bing Wu, [Kenji Watanabe](https://orcid.org/0000-0003-3701-8119), [Takashi Taniguchi](https://orcid.org/0000-0002-1467-3105), Zdeněk Sofer, Wei Zhu, Shuigang Xu

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[Electric-Field Switchable Chirality in Rhombohedral Graphene Chern Insulators Stabilized by Tungsten Diselenide](https://mdr.nims.go.jp/datasets/354581b1-0bb5-44a5-9078-cb16ee6c36d7)

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Electric-Field Switchable Chirality in Rhombohedral Graphene Chern Insulators Stabilized by Tungsten DiselenideElectric-Field Switchable Chirality in Rhombohedral Graphene Chern InsulatorsStabilized by Tungsten DiselenideJing Ding ,1,2,* Hanxiao Xiang ,1,2,* Jiannan Hua ,1,2,* Wenqiang Zhou,1,2 Naitian Liu,1,2 Le Zhang,1,2 Na Xin ,3Bing Wu,4 Kenji Watanabe ,5 Takashi Taniguchi ,6 Zdeněk Sofer,4 Wei Zhu,1,2 and Shuigang Xu 1,2,†1Key Laboratory for Quantum Materials of Zhejiang Province, Department of Physics, School of Science,Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China2Institute of Natural Sciences, Westlake Institute for Advanced Study,18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China3Department of Chemistry, Zhejiang University, Hangzhou 310058, China4Department of Inorganic Chemistry, University of Chemistry and Technology Prague,Technická 5, 166 28, Prague 6, Czech Republic5Research Center for Electronic and Optical Materials, National Institute for Materials Science,1-1 Namiki, Tsukuba 305-0044, Japan6Research Center for Materials Nanoarchitectonics, National Institute for Materials Science,1-1 Namiki, Tsukuba 305-0044, Japan(Received 11 July 2024; revised 16 January 2025; accepted 23 January 2025; published 10 March 2025)Chern insulators host topologically protected chiral edge currents with quantized conductancecharacterized by their Chern number. Switching the chirality of a Chern insulator, namely, the directionof the edge current, is highly challenging due to topologically forbidden backscattering but is ofconsiderable importance for the design of topological devices. Nevertheless, this can be achieved byreversing the sign of the Chern number. Here, we report electrically switchable chirality in rhombohedralmultilayer graphene-based Chern insulators through a topological phase transition. By introducing moirésuperlattices in rhombohedral heptalayer graphene, we observe a cascade of topological phase transitions atquarter electron filling of a moiré band with the Chern number tunable from −1, 1, to 2. Furthermore,integrating monolayer tungsten diselenide at the moiréless interface of rhombohedral decalayer grapheneand hexagonal boron nitride superlattices stabilizes the Chern insulators, enabling quantized anomalousHall resistance of h=2e2. Remarkably, the Chern number can be electrically switched using displacementfields, leading to a topological phase transition from −1 to 2. Our work establishes rhombohedralmultilayer graphene moiré superlattices as a versatile platform for topological engineering, with switchablechirality offering significant promise for integrating chiral edge currents into topological electronic circuits.DOI: 10.1103/PhysRevX.15.011052 Subject Areas: Condensed Matter Physics, Electronics,GrapheneI. INTRODUCTIONThe interplay between nontrivial band topology andstrong correlations produces exotic quantum states, such asquantum anomalous Hall insulators [1,2]. A quantumanomalous Hall insulator can support topologically pro-tected dissipationless edge states similar to those in thequantum Hall effect, but without requiring an externalmagnetic field. This property has promising applications inlow-power-consumption electronics and topological quan-tum computers [3,4]. The quantum anomalous Hall insu-lator is characterized by a quantized Hall resistanceRxy ¼ h=Ce2 accompanied by a vanishing Rxx, where his the Planck constant, e is the elementary charge, and C ≠0 is the Chern number. Experimentally, due to samplequality issues, topological systems may fail to exhibit aperfectly quantized Rxy along with a vanishing Rxx atzero magnetic field. Such states are more appropriatelydescribed as Chern insulators rather than quantum anoma-lous Hall insulators. The Chern number C is a topologicalinvariant defined by the integration of the Berry curvatureover the entire Brillouin zone, characterizing the bandtopology [5]. The value of C determines the number ofchiral edge states, while its sign determines the propagationdirection of these edge states, or the chirality. In theconventional integer quantum Hall effect, electronic states*These authors contributed equally to this work.†Contact author: xushuigang@westlake.edu.cnPublished by the American Physical Society under the terms ofthe Creative Commons Attribution 4.0 International license.Further distribution of this work must maintain attribution tothe author(s) and the published article’s title, journal citation,and DOI.PHYSICAL REVIEW X 15, 011052 (2025)Featured in Physics2160-3308=25=15(1)=011052(10) 011052-1 Published by the American Physical Societyhttps://orcid.org/0009-0009-7678-7675https://orcid.org/0009-0002-5435-8545https://orcid.org/0009-0005-7238-8731https://orcid.org/0000-0002-9293-3056https://orcid.org/0000-0003-3701-8119https://orcid.org/0000-0002-1467-3105https://orcid.org/0000-0002-0589-5291https://ror.org/05hfa4n20https://ror.org/00a2xv884https://ror.org/05ggn0a85https://ror.org/026v1ze26https://ror.org/026v1ze26https://crossmark.crossref.org/dialog/?doi=10.1103/PhysRevX.15.011052&domain=pdf&date_stamp=2025-03-10https://doi.org/10.1103/PhysRevX.15.011052https://doi.org/10.1103/PhysRevX.15.011052https://doi.org/10.1103/PhysRevX.15.011052https://doi.org/10.1103/PhysRevX.15.011052https://creativecommons.org/licenses/by/4.0/https://creativecommons.org/licenses/by/4.0/form Landau levels under high magnetic fields, allowing Cto be tuned consecutively from negative to positive valuesthrough changes in external magnetic fields or carrierdensity [6]. However, tuning C in a Chern insulator isgenerally challenging because the band topology is remark-ably robust against external perturbations. Nevertheless, theability to in situ tune C, especially to reverse its sign, iscrucial for realizing complex topological device architec-tures and holds promising applications in topologicalcircuits [7–10]. To date, Chern insulators have beenobserved in several systems, including magnetically dopedtopological insulator thin film [2], MnBi2Te4 [11], twistedgraphene [3,12], WSe2=MoTe2 moiré superlattices [13],twisted MoTe2 [14–17], and rhombohedral graphene[18–24]. However, in situ switching the sign of nonzeroC in these Chern insulators remains challenging.Rhombohedral multilayer graphene has recentlyemerged as a promising platform for exploring correlatedChern insulators [18–23]. The low-energy bands in rhom-bohedral multilayer graphene exhibit a unique power-lawenergy-dispersion relation governed by E ∼ kN, where N isthe layer number and k is the crystal momentum. Thisdispersion implies the presence of a rather flat band at lowenergy, with the flatness increasing with N, thus fosteringstrong correlations [20–22,25–34]. Furthermore, the flatsurface band in rhombohedral multilayer graphene pos-sesses nontrivial topology with valley-contrasting Chernnumbers that are tunable by an electric field, providing theessential ingredients for engineering correlated Chernstates [35]. When a moiré superlattice is introduced byaligning rhombohedral multilayer graphene to hexagonalboron nitride (h-BN), it hosts an isolated topological flatband with a nonzero Chern number. Consequently, Cherninsulators with C ¼ 1 and C ¼ 2 have been reported inrhombohedral pentalayer [18] and trilayer graphene [19],respectively. However, switching the sign of C has not yetbeen achieved. Theoretical calculations suggest that theChern states in rhombohedral graphene moiré superlatticescan be effectively tuned by an electric field, with switchableC between multiple nonzero values [36].In this work, we report the observations of Cherninsulators in singly aligned rhombohedral multilayer gra-phene and h-BN moiré superlattices. By applying a largedisplacement field (D) in heptalayer (7L) graphene, weidentify a cascade of topological phase transitions betweenmultiple nontrivial states (C ¼ −1, 1, 2) at the quarterelectron filling of the moiré band, obeying the Stredaformula. The Chern states are further stabilized by inte-grating monolayer tungsten diselenide (WSe2), whichprovides strong spin-orbit coupling (SOC) into the moiré-less interface of rhombohedral decalayer (10L) graphenesuperlattices. This integration enables the observation ofquantized anomalous Hall resistance with Rxy ∼ h=2e2down to zero magnetic field, accompanied by pronouncedmagnetic hysteresis. An electrical switch driven bydisplacement fields has been observed in rhombohedral10L graphene superlattices, leading to a topological phasetransition from C ¼ −1 to C ¼ 2. Notably, the ability toswitch the sign of the Chern number (C ¼ −1 to C ¼ 1 in7L or C ¼ 2 in 10L) demonstrates that the chirality of theChern insulators can be effectively controlled by D. Ourfindings reveal highly tunable topological states in rhom-bohedral multilayer graphene moiré superlattices.II. RESULTSA. Phase diagram of rhombohedral 7L graphenemoiré superlatticesOur device D1 was fabricated using h-BN encapsulatedrhombohedral 7L graphene, as shown in Fig. 1(a). Weemployed dual-gate structures to independently tune thecarrier density (n) and D. During the fabrication, the toph-BN was crystallographically aligned with graphene (seeSupplemental Material Fig. S1 [37]). Figure 1(d) shows then −D map of the longitudinal resistance Rxx at the basetemperature T ¼ 50 mK and B ¼ 0 T. We observed multi-ple correlated insulators on the electron-doping side,exhibiting a remarkable asymmetry with respect to D.For D > 0, a cascade of insulating states appears at moiréfilling factors of ν ¼ n=n0 ¼ 0; 1; 2; 3; 4 (n0 is the densitycorresponding to one electron per moiré unit cell). Bycomparison, for D < 0, strong insulating states areobserved only at ν ¼ 0, with weak resistance peaks atν ¼ 1; 2. This asymmetrical feature suggests a singlealignment between graphene and h-BN. The twist angleof the graphene and h-BN moiré superlattice is estimated tobe 0.86°, derived from the carrier density at full filling(ν ¼ 4 at D > 0). Notably, compared to nonaligned devi-ces, the layer antiferromagnetic (LAF) insulating statesoccurring near n ¼ 0 cm−2 and D ¼ 0 Vnm−1 are absentin our singly aligned device (see Supplemental MaterialFig. S2 [37]), indicating that the moiré potential weakensthe coupling between the top and bottom layers [22,28,30].In contrast, LAF states are preserved in singly alignedpentalayer graphene devices [18], suggesting that layernumber significantly influences the electronic states inrhombohedral graphene superlattices. A similar absenceof LAF was observed in doubly aligned rhombohedral 7Lgraphene (see Supplemental Material Fig. S2 [37]).Although the moiré superlattice and large layer numberin our devices seem to decouple the two surface layers, themoiré potential at the top interface can still influence theelectronic states at the bottom interface even with large jDj.We found in the region between D ¼ −0.750 Vnm−1 andD ¼ −0.950 Vnm−1, where the electrons are polarizedaway from the moiré interface, the weak moiré potentialacting on the distant surface could induce multiple topo-logical phase transitions. In contrast, if the moiré potentialwas strong, either occurring on the D > 0 side (seeJING DING et al. PHYS. REV. X 15, 011052 (2025)011052-2Supplemental Material Fig. S4 [37]) or in a doubly aligneddevice, only topological trivial phases were observed [30].Figures 1(e) and 1(f) show enlarged n −D maps ofsymmetrized Rxx and antisymmetrized Hall resistance Rxyat−1.0 < D < −0.7 Vnm−1, measured at B ¼ �0.5 T. Atν ¼ 1, we observed unusual large Rxy values, accompaniedby local minima in Rxx. Additionally, the sign of Rxyreverses with increasing jDj, while maintaining their largeabsolute values. In the following sections, we focus on thisregion and demonstrate that these transitions arise fromtopologically nontrivial transitions involving changes inChern numbers.B. Cascade of topological phase transitions at v= 1To unveil the origin of the anomalous Rxy and itstunability by D, we performed fan diagrams by measuringRxx and Rxy as a function of ν and B at various fixed D.Figure 2 shows the fan diagrams in the vicinity of ν ¼ 1 atfour representative values ofD. Performance at otherD canbe found in Supplemental Material Fig. S6 [37]. Theremarkable features in Fig. 2 are that at all four D, Rxyexhibits large values at low field regions fanning out fromν ¼ 1, accompanied by corresponding dips in Rxx.Additionally, Rxy reverses its signs at B ¼ 0. The disper-sions of the local maximum Rxy and the corresponding dipsin Rxx as a function of B follow the Streda formula∂n=∂B ¼ Ce=h, yielding various values of C marked inFig. 2 [38].The emergence of the extracted nonzero C utilizing theStreda formula is a hallmark of correlated Cherninsulators [21,39–45]. We exclude the possibility of quan-tum Hall states giving rise to the nonzero C for thefollowing reasons: On the one hand, at a given D, onlyspecific Chern states emerge at low field regions. This issignificantly different from the quantum Hall states, whereusually a series of C simultaneously appear, and highmagnetic field is necessary to form the Landau levels.Indeed, we observe a series of quantum Hall states fanningout from ν ¼ 0 and ν ¼ 1, gradually appearing at B > 4 T(see Supplemental Material Fig. S8 [37]). On the otherhand, within the same device, at theD > 0 side, we observetopological trivial states showing neither the abnormallarge Rxy nor nonzero C (see Supplemental MaterialFig. S4 [37]). This suggests the states at D > 0 hostdistinct topology from those at the D < 0 side.In Fig. 2, we observe strikingly D-dependent Chernstates. AtD ¼ −0.760 Vnm−1, a Chern state with C ¼ −1dominates at low magnetic fields. Another Chern state withC ¼ 1 gradually emerges at B > 2 T. When decreasing Dto −0.840 Vnm−1, the C ¼ 1 state extends to the low-fieldregion and wins in the competition with the C ¼ −1 state atFIG. 1. Phase diagram of rhombohedral 7L graphene moiré superlattices (device D1). (a) Schematic of the device structure. The moirésuperlattice is formed at the interface between graphene and top h-BN. The red arrow illustrates the direction of the positive D. (b)Optical image of the final device with a standard Hall bar geometry. The scale bar is 2 μm. (c) Topological flat band of rhombohedralheptalayer graphene moiré superlattices calculated based on the Hartree-Fock method. The calculated Chern number of the isolated band(red color) has a nonzero number of 1, indicating the topological nontrivial characteristic. (d) Longitudinal resistance Rxx as a function ofthe filling factor ν and D at B ¼ 0 T. The top x axis labels the corresponding carrier density n. The black dashed box highlights theregion of interest in the main text. (e),(f) Enlarged phase diagram in the region highlighted by the black dashed box in (d), showing thesymmetrized Rxx (e) and antisymmetrized Hall resistance Rxy (f) as a function of ν and D. The data were measured at B ¼ �0.5 T. Atν ¼ 1, anomalously large Rxy emerge with both positive and negative signs tunable byD. All data were measured at the base temperatureof T ¼ 50 mK.ELECTRIC-FIELD SWITCHABLE CHIRALITY IN … PHYS. REV. X 15, 011052 (2025)011052-3B < 0.4 T. Further decreasing D to −0.900 Vnm−1, athird Chern state with C ¼ 2 emerges and participates inthe competition. It dominates over the other two states atB < 1 T. The C ¼ −1 is expelled to the high-magnetic-field region, while C ¼ 1 gradually smears. At D ¼−0.920 Vnm−1, the C ¼ 2 state completely occupies theentire phase diagram. The coexistence of multiple Chernstates with C ¼ −1; 1; 2 and their competitions can also beobserved by performing ν −D maps at fixed magneticfields (see Supplemental Material Fig. S7 [37]). Thecascade of topological phase transitions at ν ¼ 1 observedin our rhombohedral 7L graphene moiré superlatticesdiffers from that in pentalayer graphene, where onlyC ¼ 1 was observed [18]. The electric-field tunability ofmultiple topological nontrivial states, especially the sign ofnonzero C, offers a unique platform for topologicalengineering.C. Quantized anomalous Hall effects stabilized byWSe2In device D1, we observe only infantile ferromagneticstates (see Supplemental Material Fig. S14 [37]). To extendthe Chern states into zero magnetic fields, we employed astructure of graphene proximitized by a transition metaldichalcogenide layer. Previous studies on twisted bilayergraphene and rhombohedral multilayer graphene haveshown that ferromagnetic states and Chern insulators aresignificantly enhanced when graphene is in contact with aWSe2 or WS2 layer with strong SOC [20,21,46]. Inrhombohedral graphene moiré superlattices, Chern statesemerge when electrons are polarized away from the moiréinterfaces, allowing us to further incorporate the effectsof SOC.To this end, we fabricated a rhombohedral 10L graphenemoiré superlattice using a monolayer WSe2 as the topsubstate at the moiréless interface (device D2), as shownin Fig. 3(a). At the bottom surface, the graphenewas directlyin contact and crystallographically aligned with h-BN,forming the moiré superlattices. To unveil the role of SOCinduced byWSe2, we alsomeasured the transport behavior ofintrinsic rhombohedral 10L graphene moiré superlatticeswithout WSe2 (device D3). Devices D3 and D2 share thesame stack and underwent the same fabrication process,resulting in the same moiré wavelength with a twist angle of0.58°, allowing us to directly compare scenarios with andwithout SOC. We found that intrinsic rhombohedral 10Lgraphene moiré superlattices (device D3) did not exhibit anytopological features at either the moiré or moiréless interface(see Supplemental Material Fig. S13 [37]), unlike rhombo-hedral 7L graphene. This difference is probably due to theenhanced trigonal warping effect in thicker layers, which candisrupt the correlated flat-band characteristics [27].In contrast, we observe enhanced topological featuresmanifesting as quantized anomalous Hall effects in deviceFIG. 2. Electric- and magnetic-field-driven cascade of topological phase transitions in device D1. Rxy (a) and Rxx (b) as a function of νand B at a fixedD ¼ −0.760 Vnm−1. The dashed lines mark the Chern numbers of the topological nontrivial states C ¼ −1 and C ¼ 1.The C ¼ −1 state dominates over C ¼ 1 at the low-B region. Rxy (c) and Rxx (d) as a function of ν and B at a fixedD ¼ −0.840 Vnm−1.The C ¼ 1 state becomes dominant at the low-B region. Rxy (e) and Rxx (f) as a function of ν and B at D ¼ −0.900 Vnm−1. A thirdChern state with C ¼ 2 emerges from low-field regions and participates in the competition with the C ¼ 1 and C ¼ −1 states. Rxy (g)and Rxx (h) as a function of ν and B at D ¼ −0.920 Vnm−1. The Chern state with C ¼ 2 wins the competition and dominates in theentire phase diagram. All Chen numbers are determined according to the Streda formula.JING DING et al. PHYS. REV. X 15, 011052 (2025)011052-4D2. Figure 3 presents detailed measurements of Rxx andRxy in device D2 at the base temperature. Similar to thebehavior in rhombohedral 7L graphene, topologicallynontrivial states emerge when electrons are polarizedtoward the moiréless interface, where they experiencestrong SOC from WSe2 through proximity effects. Asshown in Fig. 3(b), a local minimum in Rxx is observed atν ¼ 1 in the region 0.690 Vnm−1 < D < 0.870 Vnm−1.In the same region, Rxy in Fig. 3(d) shows an anomalouslarge value down to jBj ¼ 50 mT.To identify the topological states at ν ¼ 1, we fixed D ¼0.814 Vnm−1 and scanned the out-of-plane B forward andbackward. As shown in Fig. 3(e), Rxy displays a pro-nounced hysteresis loop with a coercive field Bc ≈ 10 mT,indicating spontaneous time-reversal symmetry breaking.The value of Rxy is quantized to h=2e2 ≈ 13 kΩ down toB ≈ 0 T, consistent with a quantized anomalous Hall statewith C ¼ 2 at given D. This quantization of Rxy is furtherconfirmed by sweeping either ν at a fixed D ¼0.814 Vnm−1 or D at a fixed ν ¼ 1, as shown inFigs. 3(h) and 3(i), respectively. Each instance of quanti-zation is accompanied by a local dip in Rxx with a valuebelow 2 kΩ. Temperature-dependent measurements of thehysteresis loops yield a magnetic Curie temperature of 4 Kand a thermal activation gap of Δ ≈ 2.0 K (seeSupplemental Material Fig. S15 [37]).D. Electric-field-driven nontrivial topological phasetransition in rhombohedral 10L grapheneBeyond observing the Chern state with C ¼ 2 atD ¼ 0.814 Vnm−1, we also find that the sign of Rxy istunable by D, similar to the behavior in 7L graphene(device D1) shown in Fig. 1(f). As illustrated in Fig. 3(d),Rxy undergoes a sign reversal around D ≈ 0.730 Vnm−1.While electrical switching of Rxy ’s sign has been previ-ously reported in twisted graphene systems [3,46,47], theunderlying mechanisms in our system differ significantly.In twisted graphene systems, the reversible Rxy appears ashysteretic behavior when sweeping either ν or D at a fixedsmall B, with sign reversals occurring within a fixed ν andD range, and the absolute value of the Chern number (jCj)remains unchanged. This phenomenon is a dramaticprocess and arises from gate-induced valley polarizationreversal [3], where the orbital magnetization changes signas different valleys are favored at a given B during eachgate sweep. In contrast, our system exhibits distinctcharacteristics that point to different mechanisms. First,no hysteresis is observed when sweeping either ν or D, asFIG. 3. Phase diagram and quantized anomalous Hall effects in rhombohedral 10L graphene moiré superlattice stabilized by WSe2(device D2). (a) Optical image (top panel) and schematic (bottom panel) of the device. The scale bar is 1 μm. The moiré superlattice isformed at the interface between graphene and bottom h-BN. (b) Rxx as a function of ν andD at B ¼ 0 T in the region where electrons arepolarized to the moiréless interface. The black dashed box highlights the region of interest discussed in the main text. Symmetrized Rxx(c) and antisymmetrized Rxy (d) as a function of ν and D at B ¼ �50 mT. The data were acquired in the region marked by the blackdashed box in (b). (e) Rxy and Rxx as a function of B swept forward and backward across zero at fixed ν ¼ 1 andD ¼ 0.814 Vnm−1. (f)Temperature-dependent magnetic hysteresis loops acquired by sweeping B forward and backward at various temperatures. (g) ExtractedRxy from the data in (f) as a function of the temperature at B ¼ �30 mT. (h) Rxy and Rxx as a function of ν swept forward and backwardat a fixed D ¼ 0.814 Vnm−1. (i) Rxy and Rxx as a function of D swept forward and backward at a fixed ν ¼ 1. The different coloredregions correspond to opposite signs of the Chern numbers. (h) and (i) were measured at a fixed B ¼ �50 mT.ELECTRIC-FIELD SWITCHABLE CHIRALITY IN … PHYS. REV. X 15, 011052 (2025)011052-5shown in Figs. 3(h) and 3(i). Second, Rxy reverses itssign at distinct D regions, with Rxy positive in therange 0.690 Vnm−1 < D < 0.730 Vnm−1 and negativein 0.730 Vnm−1 < D < 0.870 Vnm−1, as illustrated inFigs. 3(d) and 3(i). Third, a series of fan diagramsstemming from ν ¼ 1 were measured, from which Chernnumbers were extracted by the Streda formula.Figure 4 shows the evolution of topological nontrivialstates as a function of D. Obviously, the Chern state atν ¼ 1 is highly tunable by both D and B. Particularly, itundergoes a topological phase transition from C ¼ −1 toC ¼ 2 induced by tuning D at B ¼ 0. These two distincttopological states exhibit pronounced magnetic hysteresiswhen sweeping B forward and backward at fixed ν and D,as seen in Figs. 4(e)–4(h), confirming their spontaneoustime-reversal symmetry breaking. Notably, both the signand absolute value of C are tunable by D. Combining thedata from Figs. 2 and 4, we observe sign reversals of C inboth 7L and 10L graphene, suggesting that electricalswitching of chirality in rhombohedral graphene Cherninsulators is not uncommon.III. DISCUSSIONOur findings reveal a cascade of topological phasetransitions simply by tuning D, highlighting the richtopological phases in rhombohedral multilayer graphenemoiré superlattices. The nature of Chern insulators at ν ¼ 1remains elusive, despite many theoretical studies aimed atunderstanding the underlying mechanisms [18,48–52]. Thegapped states at ν ¼ 1 are believed to arise from electroninteractions, as single-particle calculations consistentlypredict gapless states [49]. Applying D can redistributethe Berry curvature within the first moiré conduction bandat the single-particle level [53]. When strong interactionsopen a gap, the Berry curvature integrated up to the Fermilevel at ν ¼ 1 can yield different integer Chern numbers fordifferent values of D, resulting in observable D-inducedtopological phase transitions. Moreover, the specific Chernnumbers may vary with the layer number of rhombohedralgraphene, as the Berry curvature distributions differ slightlyat the single-particle level. Other mechanisms, such asanomalous Hall crystals, could also contribute to thenontrivial topological phases at ν ¼ 1 [50,51].Compared to previous reports of electric-field-tunableChern insulators in various graphene-based systems[3,23,24,47,54], our work demonstrates the ability toswitch the sign of Chern numbers via topological phasetransitions, offering an essential ingredient for designingtopological circuits. Notably, edge current chirality switch-ing in Chern insulators has recently been achieved inmagnetically doped topological insulators via spin-orbittorque assisted by an applied magnetic field [8], which is anextrinsic approach. In contrast, the chirality switching inFIG. 4. Nontrivial topological phase transitions in rhombohedral 10L graphene proximitized by WSe2 (device D2). (a)–(d) Rxy as afunction of ν and B at various fixed D. The dashed lines mark the Chern numbers of topological nontrivial states following the Stredaformula. (e)–(h) Rxy as a function of B swept forward and backward across zero at fixed ν ¼ 1 and corresponding D. The coloredregions correspond to opposite signs of the Chern numbers, with light red (blue) corresponding to positive (negative) values. The insetsin each panel show enlarged views of the hysteresis loops in the low-B regions.JING DING et al. PHYS. REV. X 15, 011052 (2025)011052-6rhombohedral graphene Chern insulators here is an intrin-sic effect, achieved purely by electric-field tuning, makingit a more practical approach for topological electronics.Our observations of quantized anomalous Hall resistancewith a high Chern number (C ¼ 2) also offer new avenuesfor exploring emerging physics and low-power-consump-tion electronic applications [3,20]. Particularly, given thatrhombohedral multilayer graphene moiré superlattices cansupport fractional Chern insulators [18,48], our system mayhost tunable fractional Chern insulators with high Chernnumbers. We have already observed preliminary features ofthe anomalous Hall effect at ν < 1 (as shown inSupplemental Material Fig. S17 [37]), though it is notyet quantized.Whilewe have achieved quantized anomalous Hall effectsfor the C ¼ 2 state, the quantization of the C ¼ −1 state inboth 7L and 10L graphene remains incomplete at zeromagnetic fields. The lack of full quantization in Rxy andthe residual Rxx may be due to several factors. Unlike inpentalayer graphene [18], where only a single Chern insu-lator statewas observed, multiple Chern insulator states existin our system. At zero magnetic field, these competingtopologically nontrivial states (C ¼ −1; 1; 2) are energeti-cally close. As shown in Figs. 2 and 4, the Chern states arehighly sensitive toD, so even tiny spatial variations inD, dueto nonuniformgating, can create different Chern states acrossadjacent domains. This multidomain structure can lead tobulk dissipation and percolation transport, disrupting perfectHall quantization [55]. Applying a magnetic field canlocalize disorder, facilitate time-reversal symmetry breaking,and enlarge the topological gap, thus improving quantiza-tion, as observed in magnetic topological insulators andmagic-angle twisted bilayer graphene [39–43,56–58]. Otherpossible reasons for imperfect quantization include disorderfrom interfacial charges, twist angle inhomogeneities, ormetallic grain boundaries between domains with slightlydifferent twist angles. Additionally, reducing the electronictemperature could further enhance quantization.In summary, our findings demonstrate that rhombohedralmultilayer graphene moiré superlattices provide a fertileplatform for topological engineering. The tunability ofChern numbers in these Chern insulators offers newopportunities to design topological junctions. With multipletuning parameters, such as twist angle, strength of SOC,and layer number, rhombohedral graphene moiré super-lattices allow for versatile approaches to engineer diversetopological phases. Particularly, the role of SOC induced byproximal WSe2 in stabilizing Chern states within therhombohedral graphene moiré superlattice warrants furtherinvestigation. For instance, exploring the evolution of thephase diagram as a function of the SOC strength, which canbe tuned through precise alignment between graphene andWSe2, could provide valuable insights [59]. Our observa-tion of Chern number switching enables the creation ofChern junctions and the development of topologicalcircuits, where domains with different Chern numberscan be controlled via multiple local gates [7].Note added. Recently, we became aware of similar obser-vations reporting switchable Chern states in rhombohedralhexalayer graphene moiré superlattices under finite mag-netic fields [60].ACKNOWLEDGMENTSThis work was funded by National Natural ScienceFoundation of China (Grant No. 12274354, S. X.;No. 12474144, W. Z.), the Zhejiang Provincial NaturalScience Foundation of China (Grant No. LR24A040003and No. XHD23A2001, S. X.), the R&D Program ofZhejiang province (Grant No. 2022SDXHDX0005,W. Z.), and Westlake Education Foundation at WestlakeUniversity. We thank Chao Zhang from the Instrumentationand Service Center for Physical Sciences at WestlakeUniversity for technical support in data acquisition. Wealso thankWestlake Center for Micro/Nano Fabrication andthe Instrumentation and Service Center for MolecularSciences for facility support. K. W. and T. T. acknowledgesupport from the JSPS KAKENHI (Grants No. 21H05233and No. 23H02052) and World Premier InternationalResearch Center Initiative, MEXT, Japan. Z. S. was sup-ported by Project No. LUAUS23049 from Ministry ofEducation Youth and Sports and by the project AdvancedFunctional Nanorobots (Reg. No. CZ.02.1.01/0.0/0.0/15_003/0000444 financed by the EFRR).DATA AVAILABILITYThe raw data in the current study are available from thecorresponding author upon reasonable request.APPENDIX: METHODS1. Device fabricationMultilayer graphene was mechanically exfoliatedfrom bulk natural graphite (Graphenium Flakes, NGSNaturgraphit) onto SiO2 (285 nm)/Si substrates. The bulkWSe2 crystal was grown using chemical-vapor-transportmethods. The layer number of graphene flakes was initiallydetermined by optical contrast and further confirmed bytransport measurements (see Supplemental MaterialFig. S3, [37]). Rhombohedral stacking domains werehunted by performing Raman maps of graphene. Tostabilize the rhombohedral stacking orders in subsequentvan der Waals assembly processes, we isolated them fromBernal stacking domains by a cutting process using atungsten tip. The h-BN encapsulated rhombohedral gra-phene stacks were prepared using a standard dry transfermethod with the assistance of a poly(bisphenol A carbon-ate) and polydimethylsiloxane (PC-PDMS) stamp. Fordevice D1, during the transfer, we intentionally alignedELECTRIC-FIELD SWITCHABLE CHIRALITY IN … PHYS. REV. X 15, 011052 (2025)011052-7one of the straight edges of toph-BNwith that of thegraphene[see Supplemental Material Fig. S1(a), [37] ] and misalignedthem with that of the bottom h-BN, resulting in a singlealignment configuration. For devices D2 and D3, we firstpicked up monolayer WSe2 by the top h-BN, followed bypicking up a rhombohedral graphene flake. The heterostruc-tures were released onto a bottom h-BN and Pt bottom gate,which was prepared in advance. The graphene was inten-tionally aligned with the bottom h-BN. The alive rhombohe-dral stacking domains in the final stacks were identified by asecond Raman map, as demonstrated in SupplementalMaterial Fig. S1(d), [37]. We further used atomic forcemicroscopy to select bubble-free regions tomake the devices.For device fabrication, standard e-beam lithography, induc-tively coupled plasma, and e-beam evaporation wereemployed to design a multiterminal Hall bar geometry.Contact electrodes were made by selectively etching thetop h-BN and evaporating Cr and Au (3 and 60 nm,respectively) on top of the exposed multilayer graphene.2. Transport measurementLow-temperature electronic-transportmeasurementswereconducted in a dilute refrigerator (Oxford Triton) with a basetemperature of 50 mK. A standard low-frequency lock-intechnique (SR830) at a frequency of 17.7 Hz was used tomeasure the longitudinal and Hall resistance of a Hall bardevice. The ac excitation current was set to 1–10 nA. Gatevoltages were applied using a Keithley 2614B.Dual-gate structures were utilized to independentlytune the total carrier density n and the displacementfield D. Their values were converted from the top gate(V t) and bottom gate (Vb) voltages using a parallelplate capacitor model: n ¼ ðCbΔVb þ CtΔV tÞ=e andD ¼ ðCbΔVb − CtΔV tÞ=2ε0, whereCbðCtÞ are the bottom-(top-) gate capacitances per unit area, ΔVb ¼ Vb − V0b(ΔV t ¼ V t − V0t ) are the effective bottom (top) gate volt-ages, e is the elementary charge, and ε0 is the vacuumpermittivity. 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RESULTS A. Phase diagram of rhombohedral 7L graphene moiré superlattices B. Cascade of topological phase transitions at v=1 C. Quantized anomalous Hall effects stabilized by WSe2 D. Electric-field-driven nontrivial topological phase transition in rhombohedral 10L graphene III. DISCUSSION Note added.  ACKNOWLEDGMENTS DATA AVAILABILITY APPENDIX: METHODS 1. Device fabrication 2. Transport measurement 3. Symmetrized Rxx and antisymmetrized Rxy References