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Yanyu Jia, Tiancheng Song, Zhaoyi Joy Zheng, Guangming Cheng, Ayelet J. Uzan, Guo Yu, Yue Tang, Connor J. Pollak, Fang Yuan, Michael Onyszczak, [Kenji Watanabe](https://orcid.org/0000-0003-3701-8119), [Takashi Taniguchi](https://orcid.org/0000-0002-1467-3105), Shiming Lei, Nan Yao, Leslie M. Schoop, N. P. Ong, Sanfeng Wu

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[Anomalous superconductivity in twisted MoTe            <sub>2</sub>            nanojunctions](https://mdr.nims.go.jp/datasets/4a34f6ef-5a5a-43bd-9a12-b28641d56c42)

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Anomalous superconductivity in twisted MoTe2 nanojunctionsJia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e1 of 8C O N D E N S E D  M AT T E R  P H Y S I C SAnomalous superconductivity in twisted MoTe2 nanojunctionsYanyu Jia1*†, Tiancheng Song1†, Zhaoyi Joy Zheng1,2, Guangming Cheng3, Ayelet J. Uzan1,  Guo Yu1,2, Yue Tang1, Connor J. Pollak4, Fang Yuan4, Michael Onyszczak1, Kenji Watanabe5,  Takashi Taniguchi6, Shiming Lei7, Nan Yao3, Leslie M. Schoop4, N. P. Ong1, Sanfeng Wu1*Introducing superconductivity in topological materials can lead to innovative electronic phases and device func-tionalities. Here, we present a unique strategy for quantum engineering of superconducting junctions in moiré materials through direct, on-chip, and fully encapsulated 2D crystal growth. We achieve robust and designable superconductivity in Pd-metalized twisted bilayer molybdenum ditelluride (MoTe2) and observe anomalous su-perconducting effects in high-quality junctions across ~20 moiré cells. Unexpectedly, the junction develops en-hanced, instead of weakened, superconducting behaviors, exhibiting fluctuations to a higher critical magnetic field compared to its adjacent Pd7MoTe2 superconductor. In addition, the critical current further exhibits a notable V-shaped minimum at zero magnetic field. These features are unexpected in conventional Josephson junctions and absent in junctions of natural bilayer MoTe2 created using the same approach. We discuss implications of these observations, including the possible formation of mixed even- and odd-parity superconductivity at the moiré junctions. Our results also demonstrate a pathway to engineer and investigate superconductivity in frac-tional Chern insulators.INTRODUCTIONRecent observations of fractional quantum anomalous Hall effect (1–3) in twisted bilayer molybdenum ditelluride (tMoTe2) (4–6) have confirmed the existence of fractional Chern insulators (FCIs) (7–13) in the absence of magnetic fields. The creation of superconductivity (SC) in FCIs can in principle lead to interesting electronic states of matter under unexplored experimental condi-tions (14, 15). However, it is challenging to create SC using tradi-tional means in such air-sensitive two-dimensional (2D) moiré materials. Here, we overcome such challenges by presenting a unique strategy for constructing high-quality superconducting junctions consisting of air-sensitive van der Waals (vdW) moiré materials, such as tMoTe2. We present systematic characteriza-tions of the junction, including both the atomic structure and the electronic transport behaviors.RESULTSvdW-encapsulated 2D growth and nanojunctionsThe key to our approach of fabricating high-quality supercon-ducting moiré junctions is the recently introduced on-chip 2D growth mechanism (16), which is based on the unexpected dis-covery of a rapid mass transport and crystal growth templated on 2D materials. The air-sensitive 2H-MoTe2 flakes, in contact with predeposited palladium (Pd) source, are together fully encapsu-lated between top and bottom graphite/hexagonal boron nitride (hBN) stacks. The Pd serves as the seed of growth in the next step [see Fig. 1 (A and B) for cartoon illustrations of the device and the crystal structure]. The device as fabricated contains no supercon-ducting materials (neither Pd nor MoTe2 superconducts). We then anneal the device at ~185°C, which triggers the transport of an ultrathin uniform layer of Pd into MoTe2 layer, and their reac-tions produce a new crystalline compound Pd7MoTe2, which can be seen as the darker region extending from the Pd contacts in the optical image of the final device after annealing (Fig. 1C). All pro-cesses involving MoTe2 are implemented in an Argon-filled glove-box to prevent degradation (Materials and Methods). Detailed characterizations of such a chamber-free 2D low-temperature synthesis, generalizable to various combinations of metals and 2D materials, can be found in (16). Using this approach, we find that a class of unique Pd-based compounds produced on topological chalcogenides, including the Pd7MoTe2 synthesized here, are su-perconductors (17).Here, we demonstrate a controllable creation of high-quality superconducting junctions in bilayer MoTe2 in both its natural and twisted forms. Figure 1 (D to G) shows a typical growth of Pd7MoTe2 on tMoTe2 in device D1 in which we record the syn-thesis process under an atomic force microscope (AFM) after se-lected growth elapsed time. The length of the tMoTe2 junction between two Pd7MoTe2 islands can be accurately determined by controlling the growth time. The increased thickness in the vdW stack due to the Pd spread is ~1.5 nm (Fig. 1H), consistent with our previous report (16).Atomic characterization of the junctionWe first characterize the new compound Pd7MoTe2 and the nano-junction using a scanning transmission electron microscope (STEM), following the fabrication and experimental procedures described in (16, 18) for both cross section and plan-view STEM 1Department of Physics, Princeton University, Princeton, NJ 08544, USA. 2Depart-ment of Electrical and Computer Engineering, Princeton University, Princeton, NJ 08544, USA. 3Princeton Materials Institute, Princeton University, Princeton, NJ 08544, USA. 4Department of Chemistry, Princeton University, Princeton, NJ 08544, USA. 5Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan. 6Research Center for Mate-rials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan. 7Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, China.*Corresponding author. Email: sanfengw@​princeton.​edu (S.W.); yanyuj@​princeton.​edu (Y.J.)†These authors contributed equally to this work.Copyright © 2025 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY). Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025mailto:sanfengw@​princeton.​edumailto:yanyuj@​princeton.​edumailto:yanyuj@​princeton.​eduhttp://crossmark.crossref.org/dialog/?doi=10.1126%2Fsciadv.adq5712&domain=pdf&date_stamp=2025-01-29Jia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e2 of 8studies. Figure 2A shows a STEM image of a suspended tMoTe2 film placed on a Pd-deposited TEM grid (sample T1), after the heat treatment at 190°C for 6 min. The lateral growth of the com-pound (brighter area) from the Pd outer seed leads to a junction of Pd7MoTe2/tMoTe2/ Pd7MoTe2 where the tMoTe2 gap is about 30 nm wide. We performed energy-dispersive x-ray (EDX) spectroscopy analysis on the film (Fig. 2B) and confirmed that the atomic ratio of Pd/Mo/Te in the compound is always very close to 7:1:2. Figure S1 shows EDX analysis on other locations that are well separated, con-firming the uniformity of the as-grown material. Figure 2C displays high-angle annular dark-field (HAADF) images with an atomic resolution, which clearly reveals both a crystalline structure of the Pd7MoTe2 and the moiré lattice of tMoTe2. The fast Fourier trans-form (FFT) pattern of the region tMoTe2 (Fig. 2D) confirms its lat-tice structure as well as a twist angle of 3.7°, which is the target angle during fabrication. The FFT pattern of Pd7MoTe2, as shown in Fig. 2E, is indistinguishable from our previous observation (16) of Pd7WTe2, implying that the two crystal structures are the same. It is remarkable that an exceptionally sharp lateral interface (<1 nm) between Pd7MoTe2 and tMoTe2 is achieved and that the moiré structure of tMoTe2 remains intact in the junction (Fig. 2F). Figure S2 shows the cross-sectional STEM images taken from a Pd7MoTe2/tMoTe2 device (sample T2) grown inside a vdW stack fully encap-sulated by hBN, like the transport device shown in Fig. 1. The data there again confirm the high quality of the junction.We note that in regular devices with prepatterned contacts, the moiré structure near the contact region (within ~10 nm laterally) is typically distorted or even destroyed. The realization of a uniform moiré pattern extending to nearly atomically close to the metal con-tact in our experiment is outstanding. Our gentle and low-temperature growth helps improve and protect the moiré homogeneity because the ultrathin Pd film serves as a glue that seals the two MoTe2 mono-layers, an advantage of our approach.Anomalous SC in tMoTe2 junctionsIn the transport study of this work, we focus on SC properties of junctions with a width d ~ 100 nm, which we call short junctions. We demonstrate that SC is achieved across the junction of tMoTe2 in device D2, fabricated with an interlayer twist angle of ~3.7° and a junction d ~ 105 nm (across ~20 moiré cells) (Fig. 3, A and B). Figure 3A illustrates our transport measurement scheme that de-tects the voltage drops both on the Pd7MoTe2 and across the tMoTe2 junction when current passes through. The measured resistances (Rxx) versus temperature (T) exhibit sharp decreases to zero just be-low ~1 K for both Pd7MoTe2 superconductor (17) and the tMoTe2 junction (Fig. 3C). The IV characteristics across the junction (Fig. 3D) display the expected SC nonlinearity and a sharp transition at a critical current (Ic) of ~42 nA. The differential resistance dV/dI ver-sus applied dc current (I), taken for both Pd7MoTe2 and the junc-tion, reveals a smaller critical current across the junction (Fig. 3E).EPd7MoTe2185 °C, 15 minF185 °C, 22 min275nmBefore annealingDPd1.3 µm0 13H (nm)400 nmG185 °C, 27 minAPd sourcePd7MoTe2Junction4 µmC D1H (nm)Position (nm)0210 800400H1.5nmMoTeB tMoTe2Moiré latticeθ = 3.7°θ  3.7Sideview5 nmD1tMoTe2400nm170nmGrtMoTe2hBNPdFig. 1. vdW-encapsulated, on-chip 2D growth on moiré materials and tMoTe2 junctions. (A) Cartoon illustration of the growth of Pd7MoTe2 superconductors and the device design. The cross-sectional device structure is illustrated in the inset at the bottom right. The junction including tMoTe2, Pd7MoTe2, as well as the Pd seed is fully encapsulated by the top and bottom graphite/hBN stacks. (B) tMoTe2 crystal lattice at an interlayer twist angle of ~3.7°. (C) Optical image of a typical device after on-chip growth. The darker regions extended from Pd contacts are thin Pd7MoTe2. (D to G) A series of AFM images of junction taken during a typical growth process with tem-perature and elapsed times is indicated below the images. The length of the tMoTe2 junctions is indicated by the red texts. (H) AFM height profiles along the solid lines indicated in (G) with matched color.Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025Jia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e3 of 8However, we observe major differences between the moiré junc-tions and a conventional Josephson junction. The first hint of anom-aly is that the SC fluctuations of the junction exist up to a higher temperature than Pd7MoTe2. As shown in Fig. 3C, we characterize the superconducting transition by presenting Tc,3%, Tc,50%, and Tc,90%, defined as the temperatures at which Rxx drops to 3, 50, and 90% of the normal state value, respectively. Note that, in general, Tc,3% is close to the temperature at which the 2D superconductor loses its phase rigidity, whereas Tc,90% signifies the temperature up to which substantial superconducting fluctuations (hence pair strength) are still present. In our observations, while Tc,3% of the moiré junction is lower than that of Pd7MoTe2, Tc,90% of the moiré junction (~1.2 to 1.3 K) is, however, higher (Tc,90% of Pd7MoTe2 is ~0.8 to 0.9 K). We further highlight this feature in Fig. 3 (F and G), where dV/dI curves are recorded upon warming up the device. When Pd7MoTe2 is in its normal state (T > 0.9 K), substantial nonlinearity in IV curves re-mains across the junction at ~1.5 K.The most notable features of the moiré junctions emerge when a magnetic field (B) is applied normally to the film. Figure 4 (A to D) displays the critical current behaviors of both Pd7MoTe2 and the moiré junction as a function of B. Whereas SC of Pd7MoTe2 at 50 mK is fully suppressed above ~1.2 T (Fig. 4A), features of SC at the junc-tion persist to much higher fields (~2.2 T). The contrast is most apparent in Fig. 4E, where we compare their resistive transitions versus B. Both higher Tc and higher critical B (Bc) suggest that the pairing potential in the junction is enhanced over that in the Pd7MoTe2 pads and that the usual proximity effects are not sufficient to explain our data. The data suggest that SC with a pairing potential distinct from that in Pd7MoTe2 appears to reside in the junction.This is accompanied by another unexpected feature in the field profile of the critical current. In a conventional Josephson junction, winding of the supercurrent phase results in a pattern in which Ic peaks at B = 0. However, the moiré junctions exhibit a clear “V-shaped” minimum at zero B, as seen in Fig. 4 (B, C, and F). A differ-ent perspective of the anomalous minimum in Ic is seen if we plot dV/dI versus B with I fixed at 43 nA. We see that B drives the junc-tion from a resistive state (at B = 0) to a dissipationless SC state as B increases (Fig. 4G). These anomalies, including the enhanced criti-cal B and the V-shaped critical current minimum, are robust under repeated thermal cycling and highly reproducible across devices (see figs. S3 to S5 for data taken in another device, D3) and at all gate voltages (figs. S6 and S7).An extrinsic cause of an enhanced Ic at finite B could be a quasiparticle-induced cooling effect, which has been discussed, for example, in the context of the nanowire junctions electrically con-tacted by bulk superconductor electrodes (19). These electrodes pro-vide a cooling channel to the electrons in the junction. At finite magnetic fields, the creation of quasiparticles in the superconductor θ = 3.7°5 nm5 nmAPd depositedTEM gridC DEFtMoTe2Pd7MoTe2 tMoTe2Pd7MoTe2tMoTe2Pd7MoTe2tMoTe2Pd7MoTe20.38 nm0.22 nm0.32 nm1 nmSharp interface2 1/nm5 1/nm100 nm100 nm100 nm100 nmMo: 9.6%Pd7MoTe2tMoTe2HAADFBTe: 21.1%Pd: 69.3%Pd7MoTe2T = 190 °Ct =  6 min 200 nmT1Fig. 2. STEM analysis of tMoTe2 moiré junction with sharp interfaces. (A) STEM image of tMoTe2 after the growth of Pd7MoTe2, prepared on a TEM grid (sample T1). The TEM grid is predeposited with Pd, followed by transferring tMoTe2 on top. Subsequently, Pd is introduced by holding the temperature at 190°C for 6 min, resulting in a tMoTe2 moiré junction with a width of approximately 30 nm. Regions of different materials are indicated. (B) HAADF and corresponding elemental mappings captured at the moiré junction. The atomic ratio of Pd:Mo:Te is found to be close to 7:1:2 in the compound as grown, while negligible Pd can be observed in the neighboring tMoTe2 area. (C) An atomic-resolution STEM image of the moiré junction. (D) The FFT pattern of tMoTe2 regime, confirming the twist angle of 3.7°. (E) The FFT pattern of the crys-talline Pd7MoTe2, showing the sixfold symmetry. (F) Magnification of the STEM image at the interface marked in the red rectangle in (C). The crystalline structures of both Pd7MoTe2 and tMoTe2 can be clearly visualized, demonstrating a sharp interface between the two regions. The moiré structure of tMoTe2 remains intact.Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025Jia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e4 of 8electrodes can provide better cooling for the junction electrons, po-tentially leading to higher Ic (lower electron temperature) of the junction in finite B. This electronic cooling is optimized when the superconducting electrodes become normal. However, our devices have a very different structure compared to the nanowire devices. Our electrodes are mainly made of Pd metal (nonsuperconducting), while the small area of superconducting Pd7MoTe2 is only located at the very tip of the electrodes. Also, the tMoTe2 is encapsulated with-in the graphite/thin hBN layers, where the graphite layers provide additional cooling power (the insulating hBN layer is only ~10 nm in thickness, offering poor thermal isolation). As a result, our device structure facilitates a good thermal equilibrium even at zero B. In the section below, we perform contrast experiments between natural bi-layer and moiré bilayer junctions made using the same device geom-etry, components and fabrication process. The results, including the absence of the critical current anomaly in the natural bilayer junc-tion, directly imply that this quasiparticle-assisted cooling mecha-nism cannot be essential in our devices.A robust V-shaped minimum in Ic at zero B is quite rare. A well-known intrinsic example is the corner junction formed between a d-wave cuprate superconductor and an s-wave superconductor. In this situation, the destructive interference occurs between two spa-tially separated supercurrents with a relative phase shift of π (20). Likewise, destructive supercurrent interference can also be observed between spatially separated 0- and π-junctions in superconductor/ferromagnet/superconductor (SFS) junctions (21). In both cases, unconventional pairing and interference effects are key ingredients. We note an important distinction between our moiré junctions and SFS junctions. To see a V-shaped minimum in SFS junctions, one has to fine-tune the junction length d to subnanometer accuracy be-cause the exchange splitting energy causes the sign of the Josephson coupling to oscillate rapidly with a spatial period of ~1 nm (21). By contrast, the V-shaped minimum here is observed in all devices without fine-tuning d (e.g., d ~ 105 nm in D2 and ~90 nm in D3). In addition, the time reversal symmetry is preserved in our junction. Guided by the corner-junction experiment on cuprate supercon-ductors, we reason that the presence of destructive interference at the junction is needed for explaining the observed V-shaped mini-mum. Yet, the situation is also distinct from the cuprate corner junc-tion since, in our case, the device is better described as a single junction without a corner geometry.One possibility to reconcile all the experimental facts is to attri-bute such a destructive interference effect to the coexistence of an odd- and an even-parity condensate in the moiré junction. Both time reversal and inversion symmetries play key roles in the electron pair-ing of SC. In the presence of both symmetries, the conventional Bardeen-Cooper-Schrieffer theory favors an even-parity spin-singlet pairing. However, in the absence of either symmetry, unconventional dV/dI(kilohm)0816I (nA)-500 -250 0 250 500Moiré junction×50Pd7MoTe2ET(K)0.10.81.5I (nA)-500 0 500G Pd7MoTe20 60 120dV/dI (ohm)-250 250T(K)0.10.81.5I (nA)-100 0 100F Moiré junction0 6 12dV/dI (kilohm)Vxx(µV)I (nA)-60 0 60-30 300300-300150-150D0.1 K1 KStep0.1 KMoiré junctionA Moiré junction~Vxx1JunctionPd7MoTe2(SC)tMoTe2Vxx2D2B1 µm15.30H(nm)400 nmSCSCRxx(kilohm)T (K)0 1 2×100Pd7MoTe2CMoiré junction084D2Tc,50% = 0.78 KTc,50% = 0.88 KATc,3% = 0.71 KTc,3% = 0.64 KTc,90% = 1.19 KTc,90% = 0.81 KFig. 3. SC across the tMoTe2 moiré junction. (A) Cartoon illustration of transport measurement scheme. Vxx1 and Vxx2 are voltage drops recorded on Pd7MoTe2 and across the moiré junction, respectively. (B) Optical (left) and AFM (right) images of D2 (moiré junction; twist angle, ~3.7°). (C) Resistance as a function of T, for both Pd7MoTe2 (red) and the junction (blue). The critical temperatures, Tc,3%, Tc,50%, and Tc,90%, are indicated. (D) IV characteristic curves for the moiré junction, taken at various T as indicated. (E) Differential resistance (dV/dI) versus an applied dc current (I) to the source, for both Pd7MoTe2 (red) and the junction (blue). (F) dV/dI versus I taken across the moiré junction under varying T. (G) The same dV/dI map for Pd7MoTe2 superconductor. T = 0.9 K is indicated by white dotted lines in both (F) and (G) as reference.Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025Jia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e5 of 8pairing may occur. Particularly in materials with strong spin-orbit coupling (SOC) and broken inversion symmetry, SC with mixed even- and odd-parity states are anticipated (22–24). The possibility of unconventional pairing in noncentrosymmetric materials, e.g., heavy fermion systems, has been explored in the past decades (23–25), al-though challenges in confirming an odd-parity superconductor re-main. In our devices, the SOC is quite large in tMoTe2, and the moiré lattice lacks inversion symmetry. Theoretically, this can lead to ad-mixtures of even- and odd-parity pair condensates (22–27) in the moiré junction. We hence speculate that such a mixed pairing con-densate may be responsible for generating two supercurrent channels with a π phase shift that destructively interfere. Whether the two channels are spatially overlapping or spontaneously separated awaits further experimental tests.Unusual normal state conduction in the junctionWe further remark on the normal state resistance observed in short junctions (d, ~100 nm). MoTe2 is an insulator with a large activation gap (Δ, ~1 eV). However, in short junctions, we observe metallic behavior (even without applying a gate voltage) with a normal state resistance of several kilohms that is nearly T independent up to room temperature (Fig. 3C and figs. S3 and S8). The normal state resistance also exhibits little gate dependence (fig. S8). Below Tc, these metallic-like junctions exhibit supercurrents as described. We note that the atomic resolution STEM studies of the junction (Fig. 2 and fig. S2) confirm the absence of Pd atoms in the tMoTe2 region in the junction, and the moiré structure remains unchanged. Although it is possible that some disorders are still present in the junctions, they are unlikely to be responsible for the residual conduction, which is highly consistent across different devices. Conduction due to tunneling events between rare hopping sites caused by disorders should strongly depend on temperature, in contrast to our experi-mental observations (fig. S8A).One possible explanation for the unusual residual conduction is to assume that the band-bending effects close to the metallic Pd7MoTe2 pads could cause conduction channels in tMoTe2 junc-tion to be populated. Although such an effect is expected at a metal-semiconductor interface, how it occurs in the ~100-nm bilayer MoTe2 junctions require careful consideration. As a comparison, we found that such residual conduction is absent in a monolayer MoTe2 junction with a width of ~65 nm fabricated using the same approach (see fig. S9). In addition, the induced electron density needed in the bilayer junctions seems quite high in this picture, since we cannot deplete it with electrostatic gating. The weak temperature depen-dence of the conductance in the normal state provides future con-straints on its mechanism. We also suspect that the conduction may -100 100T = 500 mKC0I (nA)-100DT = 800 mK0 100I (nA)0 9 18dV/dI (kilohm)B (T)1010.50.5I (nA)---500 0 5000 40 80dV/dI (ohm)T = 50 mKA Pd7MoTe2B (T)3210123I (nA)----100 0 100T = 50 mKB Moiré junction×100Pd7MoTe2Moiré junctionRxx  (kilohm)0105B (T)E0 1 2 3I (nA)805530B (T)0.8- -0.4 0.80.40eT = 50 mK0 10 20dV/dI (kilohm)F1- -0.5 10.50dV/dI(kilohm)02040400 mK500 mK50 mKB (T)I = 43 nAGMoiré junctionT = 50 mKFig. 4. Anomalies of the superconducting moiré junction. (A) dV/dI versus I of the Pd7MoTe2 superconductor under varying magnetic field (B), taken at T = 50 mK. (B) The same map but for the moiré junction, at T = 50 mK. (C and D) The same map of the junction at T = 500 mK (C) and 800 mK (D), respectively. (E) Resistance as a function of B, for both Pd7MoTe2 (red) and the junction (blue). (F) dV/dI map taken under varying B and I, at 50 mK, highlighting the V-shaped critical current minimum at zero B. (G) dV/dI versus B, taken at a fixed dc current of 43 nA, under three different T as indicated.Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025Jia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e6 of 8be via some hidden 1D electronic channels in the junction. Note that, for longer junctions with d > 500 nm, our experiments do show that the gate-tuned insulator state of tMoTe2 is recovered, fol-lowing expectations. We now do not have a comprehensive explana-tion considering all the experimental facts. Future experiments, such as low-temperature scanning tunneling microscopy, would help resolve the situation.Although the exact mechanisms for the normal state conduction and SC remain to be worked out, we next show that (i) the metallic-ity in these short junctions occur for both tMoTe2 and natural bi-layer MoTe2, and yet (ii) only the tMoTe2 junction exhibits the superconducting anomalies. Namely, both the V-shaped minimum and the enhanced pair potential vanish if we perform the same ex-periments on the inversion symmetric natural bilayer.Contrasting behaviors in a natural bilayer junctionWe now repeat the experiments described above on natural bilayer 2H-MoTe2, which hosts an inversion center located in the middle of the two layers (Fig. 5, A and B). The junction is fabricated using the same approach, with a similar length d ~ 100 nm. Both the unusual normal state conduction and the SC are consistently observed in the natural bilayer junction, yet the anomalous supercurrent features seen in tMoTe2 are now absent. Figure 5 (C to E) and fig. S10 display the T-dependent resistances of both the natural bilayer junction and the Pd7MoTe2 in the same device, similar to previous discussions. Characteristics of the Pd7MoTe2 superconducting pads in this de-vice (D4) are closely similar to those in the moiré devices (D2 and D3), with similar values for the normal state resistance. The values of Ic when measured across the junctions are also similar. Tc of the junction is now slightly lower than the Pd7MoTe2 SC (Fig. 5C). The SC anomalies are now absent in the natural bilayer junction. (i) Bc of the junction also no longer exceeds that of Pd7MoTe2 (both ~1.2 T) (Fig. 5, F and G). Note that slight variance (±0.1 T) in Bc of Pd7MoTe2 found in different devices, especially between those grown on a natural bilayer and a moiré bilayer, could come from different levels of disorders and impurities in the compounds. Crucially, (ii) the V-shaped minimum in the Ic at zero B is now replaced by the conventional maximum as seen in Fig. 5 (G to I). The absence of the SC anomalies is confirmed at all gate voltages in the natural bilayer device (fig. S11). We further note that the anomalies we found here are also absent in Josephson junctions made of few layer WTe2 (28–30). We conclude that key properties of the tMoTe2 moiré junction, DT(K)0.10.81.5I (nA)150 0 15075 75Natural bilayer junction0 6 12dV/dI (kilohm)B(T)1010.50.51.51.5I (nA)700 0 700---- -350 3500 60 120dV/dI (ohm)FPd7MoTe2 T = 50 mK0.10.81.5T(K)I (nA)700 0 700- - - -350 3500 80 160dV/dI (ohm)E Pd7MoTe2I (nA)-150 0 150-75 75HT = 500 mKI (nA)-150 0 150-75 75T = 50 mKGNaturalbilayerjunction0 6 12dV/dI (kilohm)B(T)1010.50.51.51.5I (nA)150 0 150---- -75 75T = 630 mKIMo TeA Natural bilayer MoTe2Inversioncenter2 µmD4B100 nm100nmPd7MoTe22H bilayerMoTe2Rxx(kilohm)073.5T (K)0 1 2Natural bilayerjunctionPd7MoTe2×80C D4Tc,50% = 0.87 K130H(nm)Tc,3% = 0.77 KTc,3% =0.55 KTc,50% =0.77 K Tc,90% = 0.92 KTc,90% = 1.03 KFig. 5. Absence of anomalies in the inversion symmetric bilayer junction. (A) Cartoon illustration of exfoliated natural bilayer 2H-MoTe2 lattice structure, where the inversion center is indicated. (B) An optical image (left) of a natural bilayer device after growth and a corresponding AFM image of the junction (right). (C) Resistance versus T, taken for Pd7MoTe2 (red) and the natural bilayer junction (blue) in this device. The same measurement geometry as Fig. 3A is used. The critical temperatures, Tc,3%, Tc,50%, and Tc,90%, are indicated. (D) dV/dI map of the junction taken under varying I and T, showing the SC state. (E) The same map but for the Pd7MoTe2 SC. (F) dV/dI map of Pd7MoTe2, taken under varying I and B. T = 0.9 K is indicated by the black dotted lines in both (D) and (E) as reference. (G to I) The same dV/dI maps as (F) but taken for the junction, at three different T as indicated in the maps.Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025Jia et al., Sci. Adv. 11, eadq5712 (2025)     29 January 2025S c i e n c e  A d v a n c e s  |  R e s e ar  c h  A r t i c l e7 of 8including the absence of inversion symmetry, are responsible for the superconducting anomalies.DISCUSSIONFuture experimental and theoretical studies are necessary to uncov-er the underlying physics. While the understanding of the SC pair-ing symmetry certainly requires future experiments, the approach here based on moiré materials suggests a promising strategy to study unconventional pairing in noncentrosymmetric superconductors. The sharp interface between Pd7MoTe2 and tMoTe2 also implies a realistic route for engineering SC in moiré topological materials with the goal of proximitizing fractionalized states. Our current de-vices have a twist angle of ~3.7°, which has been shown to host the integer and FCI states upon electrostatic gating (1, 2, 4–6). Prelimi-nary results in the current devices reveal a weak but interesting gate modulation of the junction critical current (fig. S12). Investigating the coexistence of SC and FCI states is possible with further optimi-zation of the devices.MATERIALS AND METHODSDevice fabricationTransport devices (D1 to D4)hBN and graphite flakes were exfoliated on SiO2/Si substrates, identi-fied, and characterized under optical microscopes and AFM (Bruker Dimension Edge or Bruker Dimension Icon). Subsequently, hBN flakes were stacked on top of graphite flakes and then placed on SiO2/Si substrates. Electron beam lithography, followed by cold develop-ment, reactive ion etching and metal deposition, were used to create Pd contacts and growth seeds (~20-nm thick) on the bottom hBN/graphite stack. Before final assembly, the bottom stacks were then tip cleaned using AFM under the contact mode. To prepare the top stacks, we exfoliated monolayers and bilayers 2H-MoTe2 in an Ar-filled glovebox. For tMoTe2 devices (D1, D2, and D3), monolayer MoTe2 was cut into two pieces using a sharp tungsten tip. The first piece was picked up by the top vdW stack consisting of hBN and graphite flakes. The second piece of MoTe2 underwent a 3.7° rotation before being stacked with the first piece. For devices D4 and D5, natural bilayer and monolayer MoTe2 were directly picked up by a top hBN/graphite stack. The top stacks of MoTe2/hBN/graphite, for both types of devic-es, were then carefully aligned and positioned on the prepared bottom stacks. The devices prepared above were then AFM tip cleaned before being placed on a hot plate for the on-chip growth of Pd7MoTe2. With controlled temperature and time, the Pd growth process was carefully monitored under an optical microscope and an AFM. To achieve pre-cise control, devices are initially monitored under an optical micro-scope until the two Pd7MoTe2 pads are approximately 500 nm apart. Then, according to the estimated growth rate, the devices are exam-ined under AFM after each short-time extra growth to achieve the targeted junction length. The entire process involving MoTe2 was per-formed in a glovebox filled with argon, with concentrations of H2O < 0.1 parts per million (ppm) and O2 < 0.1 ppm.TEM devices (T1 and T2)The suspended TEM device (T1) was fabricated by stacking a 3.7° tMoTe2 onto a Pd-coated TEM grid using standard dry transfer tech-nique. The polycarbonate (PC) used for the dry transfer was later re-moved by dissolving in chloroform for 30 min. Pd was introduced into the tMoTe2 by holding the TEM grid at 190°C for 6 min inside the vacuum chamber of STEM. For the TEM cross-sectional device (T2), the tMoTe2 stack and Pd7MoTe2 growth were created using the same process as for transport devices. A lamella specimen was then extracted from a selected region of the stack using a standard lift-out technique within a focused ion beam–scanning electron microscope system. The specimen was further thinned and polished using a Ga⁺ ion beam until it became sufficiently transparent for STEM analysis. All fabrication steps of both devices, including the removal of the PC layer, were conducted in an Ar-filled glovebox with H2O < 0.1 ppm and O2 < 0.1 ppm. More fabrication details can be found in (16–18).Transport measurementsThe electrical transport measurement was conducted in a dilution refrigerator equipped with a superconducting magnet and a base temperature of ~20 mK. Four-probe resistance measurements were performed using the standard ac lock-in technique with a low fre-quency, typically ~23.3 Hz, and an ac current excitation from 0.5 to 10 nA. 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Electric transport measurement is partially supported by NSF through the Materials Research Science and Engineering Center (MRSEC) program of the National Science Foundation (DMR-2011750) through support to L.M.S. and S.W. and a CAREER award (DMR-1942942) to S.W. Device fabrication is partially supported by ONR through a Young Investigator Award (N00014-21-1-2804) to S.W. N.P.O. acknowledges support from the US Department of Energy (DE-SC0017863) and the Gordon and Betty Moore Foundation through Grants GBMF9466. S.W. and L.M.S. acknowledge support from the Eric and Wendy Schmidt Transformative Technology Fund at Princeton. S.W. acknowledges support from the Gordon and Betty Moore Foundation through Grants GBMF11946 and the Sloan Foundation. L.M.S. acknowledges support from the Gordon and Betty Moore Foundation through Grants GBMF9064 and the David and Lucile Packard Foundation. Y.J. acknowledges support from the Princeton Charlotte Elizabeth Procter Fellowship program. T.S. acknowledges support from the Princeton Physics Dicke Fellowship program. A.J.U. acknowledges support from the Rothschild Foundation and the Zuckerman Foundation. C.J.P. is supported by the NSF Graduate Research Fellowship Program under grant number DGE-2039656. K.W. and T.T. acknowledge support from the JSPS KAKENHI (grant numbers 21H05233 and 23H02052) and World Premier International Research Center Initiative (WPI), MEXT, Japan. S.L. acknowledges the financial support provided by the start-up fund of the Hong Kong University of Science and Technology and the Hong Kong Collaborative Research Fund (no. C6053-23G). We acknowledge the use of Princeton’s Imaging and Analysis Center (IAC), which is partially supported by the Princeton Center for Complex Materials (PCCM), a NSF Materials Research Science and Engineering Center (DMR-2011750). Author contributions: S.W. and Y.J. conceived and designed the project. Y.J. and T.S. fabricated and characterized the transport devices and performed measurements, assisted by G.Y., A.J.U., Y.T., M.O., and Z.J.Z. Y.J. and Z.J.Z. fabricated TEM samples. Y.J., Z.J.Z., G.C., and N.Y. performed STEM measurements assisted by F.Y. C.J.P., S.L., and L.M.S. grew bulk MoTe2 crystals. K.W. and T.T. provided hBN crystals. S.W., Y.J., and N.P.O. analyzed the data, interpreted the results, and wrote the paper with input from all authors. S.W. supervised the project. Competing interests: The authors declare that they have no competing interests. Data and materials availability: The data for this study have been deposited in the database Harvard Dataverse (https://doi.org/10.7910/DVN/Y5MTRI). All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials.Submitted 22 May 2024 Accepted 27 December 2024 Published 29 January 2025 10.1126/sciadv.adq5712Downloaded from https://www.science.org at National Institute for Materials Science on July 15, 2025https://doi.org/10.7910/DVN/Y5MTRIhttps://doi.org/10.7910/DVN/Y5MTRI Anomalous superconductivity in twisted MoTe2 nanojunctions INTRODUCTION RESULTS vdW-encapsulated 2D growth and nanojunctions Atomic characterization of the junction Anomalous SC in tMoTe2 junctions Unusual normal state conduction in the junction Contrasting behaviors in a natural bilayer junction DISCUSSION MATERIALS AND METHODS Device fabrication Transport devices (D1 to D4) TEM devices (T1 and T2) Transport measurements STEM measurements Supplementary Materials This PDF file includes: REFERENCES AND NOTES Acknowledgments Anomalous superconductivity in twisted MoTe2 nanojunctions INTRODUCTION RESULTS vdW-encapsulated 2D growth and nanojunctions Atomic characterization of the junction Anomalous SC in tMoTe2 junctions Unusual normal state conduction in the junction Contrasting behaviors in a natural bilayer junction DISCUSSION MATERIALS AND METHODS Device fabrication Transport devices (D1 to D4) TEM devices (T1 and T2) Transport measurements STEM measurements Supplementary Materials This PDF file includes: REFERENCES AND NOTES Acknowledgments