Evidence of the fractional quantum spin Hall effect in moiré MoTe2.

Quantum spin Hall (QSH) insulators are two-dimensional electronic materials that have a bulk band gap similar to an ordinary insulator but have topologically protected pairs of edge modes of opposite chiralities1-6. So far, experimental studies have found only integer QSH insulators with counter-propagating up-spins and down-spins at each edge leading to a quantized conductance G0 = e2/h (with e and h denoting the electron charge and Planck's constant, respectively)7-14. Here we report transport evidence of a fractional QSH insulator in 2.1° twisted bilayer MoTe2, which supports spin-Sz conservation and flat spin-contrasting Chern bands15,16. At filling factor ν = 3 of the moiré valence bands, each edge contributes a conductance 3 2 G 0 with zero anomalous Hall conductivity. The state is probably a time-reversal pair of the even-denominator 3/2-fractional Chern insulators. Furthermore, at ν = 2, 4 and 6, we observe a single, double and triple QSH insulator with each edge contributing a conductance G0, 2G0 and 3G0, respectively. Our results open up the possibility of realizing time-reversal symmetric non-abelian anyons and other unexpected topological phases in highly tunable moiré materials17-19.

Thermodynamic evidence of fractional Chern insulator in moiré MoTe2.

Chern insulators, which are the lattice analogues of the quantum Hall states, can potentially manifest high-temperature topological orders at zero magnetic field to enable next-generation topological quantum devices1-3. Until now, integer Chern insulators have been experimentally demonstrated in several systems at zero magnetic field3-8, whereas fractional Chern insulators have been reported in only graphene-based systems under a finite magnetic field9,10. The emergence of semiconductor moiré materials11, which support tunable topological flat bands12,13, provides an opportunity to realize fractional Chern insulators13-16. Here we report thermodynamic evidence of both integer and fractional Chern insulators at zero magnetic field in small-angle twisted bilayer MoTe2 by combining the local electronic compressibility and magneto-optical measurements. At hole filling factor ν = 1 and 2/3, the system is incompressible and spontaneously breaks time-reversal symmetry. We show that they are integer and fractional Chern insulators, respectively, from the dispersion of the state in the filling factor with an applied magnetic field. We further demonstrate electric-field-tuned topological phase transitions involving the Chern insulators. Our findings pave the way for the demonstration of quantized fractional Hall conductance and anyonic excitation and braiding17 in semiconductor moiré materials.

Gate-tunable heavy fermions in a moiré Kondo lattice.

The Kondo lattice-a matrix of local magnetic moments coupled through spin-exchange interactions to itinerant conduction electrons-is a prototype of strongly correlated quantum matter1-4. Usually, Kondo lattices are realized in intermetallic compounds containing lanthanide or actinide1,2. The complex electronic structure and limited tunability of both the electron density and exchange interactions in these bulk materials pose considerable challenges to studying Kondo lattice physics. Here we report the realization of a synthetic Kondo lattice in AB-stacked MoTe2/WSe2 moiré bilayers, in which the MoTe2 layer is tuned to a Mott insulating state, supporting a triangular moiré lattice of local moments, and the WSe2 layer is doped with itinerant conduction carriers. We observe heavy fermions with a large Fermi surface below the Kondo temperature. We also observe the destruction of the heavy fermions by an external magnetic field with an abrupt decrease in the Fermi surface size and quasi-particle mass. We further demonstrate widely and continuously gate-tunable Kondo temperatures through either the itinerant carrier density or the Kondo interaction. Our study opens the possibility of in situ access to the phase diagram of the Kondo lattice with exotic quantum criticalities in a single device based on semiconductor moiré materials2-9.

Excitons and emergent quantum phenomena in stacked 2D semiconductors.

The design and control of material interfaces is a foundational approach to realize technologically useful effects and engineer material properties. This is especially true for two-dimensional (2D) materials, where van der Waals stacking allows disparate materials to be freely stacked together to form highly customizable interfaces. This has underpinned a recent wave of discoveries based on excitons in stacked double layers of transition metal dichalcogenides (TMDs), the archetypal family of 2D semiconductors. In such double-layer structures, the elegant interplay of charge, spin and moiré superlattice structure with many-body effects gives rise to diverse excitonic phenomena and correlated physics. Here we review some of the recent discoveries that highlight the versatility of TMD double layers to explore quantum optics and many-body effects. We identify outstanding challenges in the field and present a roadmap for unlocking the full potential of excitonic physics in TMD double layers and beyond, such as incorporating newly discovered ferroelectric and magnetic materials to engineer symmetries and add a new level of control to these remarkable engineered materials.

Strongly correlated excitonic insulator in atomic double layers.

Excitonic insulators (EIs) arise from the formation of bound electron-hole pairs (excitons)1,2 in semiconductors and provide a solid-state platform for quantum many-boson physics3-8. Strong exciton-exciton repulsion is expected to stabilize condensed superfluid and crystalline phases by suppressing both density and phase fluctuations8-11. Although spectroscopic signatures of EIs have been reported6,12-14, conclusive evidence for strongly correlated EI states has remained elusive. Here we demonstrate a strongly correlated two-dimensional (2D) EI ground state formed in transition metal dichalcogenide (TMD) semiconductor double layers. A quasi-equilibrium spatially indirect exciton fluid is created when the bias voltage applied between the two electrically isolated TMD layers is tuned to a range that populates bound electron-hole pairs, but not free electrons or holes15-17. Capacitance measurements show that the fluid is exciton-compressible but charge-incompressible-direct thermodynamic evidence of the EI. The fluid is also strongly correlated with a dimensionless exciton coupling constant exceeding 10. We construct an exciton phase diagram that reveals both the Mott transition and interaction-stabilized quasi-condensation. Our experiment paves the path for realizing exotic quantum phases of excitons8, as well as multi-terminal exciton circuitry for applications18-20.

Quantum anomalous Hall effect from intertwined moiré bands.

Electron correlation and topology are two central threads of modern condensed matter physics. Semiconductor moiré materials provide a highly tuneable platform for studies of electron correlation1-12. Correlation-driven phenomena, including the Mott insulator2-5, generalized Wigner crystals2,6,9, stripe phases10 and continuous Mott transition11,12, have been demonstrated. However, non-trivial band topology has remained unclear. Here we report the observation of a quantum anomalous Hall effect in AB-stacked MoTe2 /WSe2 moiré heterobilayers. Unlike in the AA-stacked heterobilayers11, an out-of-plane electric field not only controls the bandwidth but also the band topology by intertwining moiré bands centred at different layers. At half band filling, corresponding to one particle per moiré unit cell, we observe quantized Hall resistance, h/e2 (with h and e denoting the Planck's constant and electron charge, respectively), and vanishing longitudinal resistance at zero magnetic field. The electric-field-induced topological phase transition from a Mott insulator to a quantum anomalous Hall insulator precedes an insulator-to-metal transition. Contrary to most known topological phase transitions13, it is not accompanied by a bulk charge gap closure. Our study paves the way for discovery of emergent phenomena arising from the combined influence of strong correlation and topology in semiconductor moiré materials.

Continuous Mott transition in semiconductor moiré superlattices.

The evolution of a Landau Fermi liquid into a non-magnetic Mott insulator with increasing electronic interactions is one of the most puzzling quantum phase transitions in physics1-6. The vicinity of the transition is believed to host exotic states of matter such as quantum spin liquids4-7, exciton condensates8 and unconventional superconductivity1. Semiconductor moiré materials realize a highly controllable Hubbard model simulator on a triangular lattice9-22, providing a unique opportunity to drive a metal-insulator transition (MIT) via continuous tuning of the electronic interactions. Here, by electrically tuning the effective interaction strength in MoTe2/WSe2 moiré superlattices, we observe a continuous MIT at a fixed filling of one electron per unit cell. The existence of quantum criticality is supported by the scaling collapse of the resistance, a continuously vanishing charge gap as the critical point is approached from the insulating side, and a diverging quasiparticle effective mass from the metallic side. We also observe a smooth evolution of the magnetic susceptibility across the MIT and no evidence of long-range magnetic order down to ~5% of the Curie-Weiss temperature. This signals an abundance of low-energy spinful excitations on the insulating side that is further corroborated by the Pomeranchuk effect observed on the metallic side. Our results are consistent with the universal critical theory of a continuous Mott transition in two dimensions4,23.

Correlated insulating states at fractional fillings of moiré superlattices.

Quantum particles on a lattice with competing long-range interactions are ubiquitous in physics; transition metal oxides1,2, layered molecular crystals3 and trapped-ion arrays4 are a few examples. In the strongly interacting regime, these systems often show a rich variety of quantum many-body ground states that challenge theory2. The emergence of transition metal dichalcogenide moiré superlattices provides a highly controllable platform in which to study long-range electronic correlations5-12. Here we report an observation of nearly two dozen correlated insulating states at fractional fillings of tungsten diselenide/tungsten disulfide moiré superlattices. This finding is enabled by a new optical sensing technique that is based on the sensitivity to the dielectric environment of the exciton excited states in a single-layer semiconductor of tungsten diselenide. The cascade of insulating states shows an energy ordering that is nearly symmetric about a filling factor of half a particle per superlattice site. We propose a series of charge-ordered states at commensurate filling fractions that range from generalized Wigner crystals7 to charge density waves. Our study lays the groundwork for using moiré superlattices to simulate a wealth of quantum many-body problems that are described by the two-dimensional extended Hubbard model3,13,14 or spin models with long-range charge-charge and exchange interactions15,16.

Simulation of Hubbard model physics in WSe2/WS2 moiré superlattices.

The Hubbard model, formulated by physicist John Hubbard in the 1960s1, is a simple theoretical model of interacting quantum particles in a lattice. The model is thought to capture the essential physics of high-temperature superconductors, magnetic insulators and other complex quantum many-body ground states2,3. Although the Hubbard model provides a greatly simplified representation of most real materials, it is nevertheless difficult to solve accurately except in the one-dimensional case2,3. Therefore, the physical realization of the Hubbard model in two or three dimensions, which can act as an analogue quantum simulator (that is, it can mimic the model and simulate its phase diagram and dynamics4,5), has a vital role in solving the strong-correlation puzzle, namely, revealing the physics of a large number of strongly interacting quantum particles. Here we obtain the phase diagram of the two-dimensional triangular-lattice Hubbard model by studying angle-aligned WSe2/WS2 bilayers, which form moiré superlattices6 because of the difference between the lattice constants of the two materials. We probe the charge and magnetic properties of the system by measuring the dependence of its optical response on an out-of-plane magnetic field and on the gate-tuned carrier density. At half-filling of the first hole moiré superlattice band, we observe a Mott insulating state with antiferromagnetic Curie-Weiss behaviour, as expected for a Hubbard model in the strong-interaction regime2,3,7-9. Above half-filling, our experiment suggests a possible quantum phase transition from an antiferromagnetic to a weak ferromagnetic state at filling factors near 0.6. Our results establish a new solid-state platform based on moiré superlattices that can be used to simulate problems in strong-correlation physics that are described by triangular-lattice Hubbard models.

Remote imprinting of moiré lattices.

Two-dimensional moiré materials are formed by overlaying two layered crystals with small differences in orientation or/and lattice constant, where their direct coupling generates moiré potentials. Moiré materials have emerged as a platform for the discovery of new physics and device concepts, but while moiré materials are highly tunable, once formed, moiré lattices cannot be easily altered. Here we demonstrate the electrostatic imprinting of moiré lattices onto a target monolayer semiconductor. The moiré potential-created by a lattice of electrons that is supported by a Mott insulator state in a remote MoSe2/WS2 moiré bilayer-imprints a moiré potential that generates flat bands and correlated insulating states in the target monolayer and can be turned on/off by gate tuning the doping density of the moiré bilayer. Additionally, we studied the interplay between the electrostatic and structural relaxation contributions to moiré imprinting. Our results demonstrate a pathway towards gate control of moiré lattices.

Evidence of high-temperature exciton condensation in two-dimensional atomic double layers.

A Bose-Einstein condensate is the ground state of a dilute gas of bosons, such as atoms cooled to temperatures close to absolute zero1. With much smaller mass, excitons (bound electron-hole pairs) are expected to condense at considerably higher temperatures2-7. Two-dimensional van der Waals semiconductors with very strong exciton binding are ideal systems for the study of high-temperature exciton condensation. Here we study electrically generated interlayer excitons in MoSe2-WSe2 atomic double layers with a density of up to 1012 excitons per square centimetre. The interlayer tunnelling current depends only on the exciton density, which is indicative of correlated electron-hole pair tunnelling8. Strong electroluminescence arises when a hole tunnels from WSe2 to recombine with an electron in MoSe2. We observe a critical threshold dependence of the electroluminescence intensity on exciton density, accompanied by super-Poissonian photon statistics near the threshold, and a large electroluminescence enhancement with a narrow peak at equal electron and hole densities. The phenomenon persists above 100 kelvin, which is consistent with the predicted critical condensation temperature9-12. Our study provides evidence for interlayer exciton condensation in two-dimensional atomic double layers and opens up opportunities for exploring condensate-based optoelectronics and exciton-mediated high-temperature superconductivity13.

PDIA3 orchestrates effector T cell program by serving as a chaperone to facilitate the non-canonical nuclear import of STAT1 and PKM2.

Dysregulated T cell activation underpins the immunopathology of rheumatoid arthritis (RA), yet the machineries that orchestrate T cell effector program remain incompletely understood. Herein, we leveraged bulk and single-cell RNA sequencing data from RA patients and validated protein disulfide isomerase family A member 3 (PDIA3) as a potential therapeutic target. PDIA3 is remarkably upregulated in pathogenic CD4 T cells derived from RA patients and positively correlates with C-reactive protein level and disease activity score 28. Pharmacological inhibition or genetic ablation of PDIA3 alleviates RA-associated articular pathology and autoimmune responses. Mechanistically, T cell receptor signaling triggers intracellular calcium flux to activate NFAT1, a process that is further potentiated by Wnt5a under RA settings. Activated NFAT1 then directly binds to the Pdia3 promoter to enhance the expression of PDIA3, which complexes with STAT1 or PKM2 to facilitate their nuclear import for transcribing T helper 1 (Th1) and Th17 lineage-related genes, respectively. This non-canonical regulatory mechanism likely occurs under pathological conditions, as PDIA3 could only be highly induced following aberrant external stimuli. Together, our data support that targeting PDIA3 is a vital strategy to mitigate autoimmune diseases, such as RA, in clinical settings.

Truncated Tau caused by intron retention is enriched in Alzheimer's disease cortex and exhibits altered biochemical properties.

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-ß plaques and Tau tangles in brain tissues. Recent studies indicate that aberrant splicing and increased level of intron retention is linked to AD pathogenesis. Bioinformatic analysis revealed increased retention of intron 11 at the Tau gene in AD female dorsal lateral prefrontal cortex as compared to healthy controls, an observation validated by quantitative polymerase chain reaction using different brain tissues. Retention of intron 11 introduces a premature stop codon, resulting in the production of truncated Tau11i protein. Probing with customized antibodies designed against amino acids encoded by intron 11 showed that Tau11i protein is more enriched in AD hippocampus, amygdala, parietal, temporal, and frontal lobe than in healthy controls. This indicates that Tau messenger RNA with the retained intron is translated in vivo instead of being subjected to nonsense-mediated decay. Compared to full-length Tau441 isoform, ectopically expressed Tau11i forms higher molecular weight species, is enriched in Sarkosyl-insoluble fraction, and exhibits greater protein stability in cycloheximide assay. Stably expressed Tau11i also shows weaker colocalization with α-tubulin of microtubule network in human mature cortical neurons as compared to Tau441. Endogenous Tau11i is enriched in Sarkosyl-insoluble fraction in AD hippocampus and forms aggregates that colocalize weakly with Tau4R fibril-like structure in AD temporal lobe. The elevated level of Tau11i protein in AD brain tissues tested, coupled with biochemical properties resembling pathological Tau species suggest that retention of intron 11 of Tau gene might be an early biomarker of AD pathology.

Interlayer Fermi Polarons of Excited Exciton States in Quantizing Magnetic Fields.

The study of exciton polarons has offered profound insights into the many-body interactions between bosonic excitations and their immersed Fermi sea within layered heterostructures. However, little is known about the properties of exciton polarons with interlayer interactions. Here, through magneto-optical reflectance contrast measurements, we experimentally investigate interlayer Fermi polarons for 2s excitons in WSe2/graphene heterostructures, where the excited exciton states (2s) in the WSe2 layer are dressed by free charge carriers of the adjacent graphene layer in the Landau quantization regime. First, such a system enables an optical detection of integer and fractional quantum Hall states (e.g., ν = ±1/3, ±2/3) of monolayer graphene. Furthermore, we observe that the 2s state evolves into two distinct branches, denoted as attractive and repulsive polarons, when graphene is doped out of the incompressible quantum Hall gaps. Our work paves the way for the understanding of the excited composite quasiparticles and Bose-Fermi mixtures.

Tuning Exciton Emission via Ferroelectric Polarization at a Heterogeneous Interface between a Monolayer Transition Metal Dichalcogenide and a Perovskite Oxide Membrane.

We demonstrate the integration of a thin BaTiO3 (BTO) membrane with monolayer MoSe2 in a dual-gate device that enables in situ manipulation of the BTO ferroelectric polarization with a voltage pulse. While two-dimensional (2D) transition metal dichalcogenides (TMDs) offer remarkable adaptability, their hybrid integration with other families of functional materials beyond the realm of 2D materials has been challenging. Released functional oxide membranes offer a solution for 2D/3D integration via stacking. 2D TMD excitons can serve as a local probe of the ferroelectric polarization in BTO at a heterogeneous interface. Using photoluminescence (PL) of MoSe2 excitons to optically read out the doping level, we find that the relative population of charge carriers in MoSe2 depends sensitively on the ferroelectric polarization. This finding points to a promising avenue for future-generation versatile sensing devices with high sensitivity, fast readout, and diverse applicability for advanced signal processing.

Exciton density waves in Coulomb-coupled dual moiré lattices.

Strongly correlated bosons in a lattice are a platform that can realize rich bosonic states of matter and quantum phase transitions1. While strongly correlated bosons in a lattice have been studied in cold-atom experiments2-4, their realization in a solid-state system has remained challenging5. Here we trap interlayer excitons-bosons composed of bound electron-hole pairs, in a lattice provided by an angle-aligned WS2/bilayer WSe2/WS2 multilayer. The heterostructure supports Coulomb-coupled triangular moiré lattices of nearly identical period at the top and bottom interfaces. We observe correlated insulating states when the combined electron filling factor of the two lattices, with arbitrary partitions, equals [Formula: see text] and [Formula: see text]. These states can be interpreted as exciton density waves in a Bose-Fermi mixture of excitons and holes6,7. Because of the strong repulsive interactions between the constituents, the holes form robust generalized Wigner crystals8-11, which restrict the exciton fluid to channels that spontaneously break the translational symmetry of the lattice. Our results demonstrate that Coulomb-coupled moiré lattices are fertile ground for correlated many-boson phenomena12,13.

Plasma-derived from human umbilical cord blood restores ovarian function and improves serum reproductive hormones levels in mice with premature ovarian insufficiency (POI) through cytokines and growth factors.

Premature ovarian insufficiency (POI) patients experience a decline in ovarian function and a reduction in serum reproductive hormones, leading to a significant impact on the outcomes of assisted reproductive technology. Despite the absence of an effective clinical treatment to restore fertility in POI patients, recent research has indicated that cord blood plasma (CBP) derived from human umbilical cord blood (hUCB) may offer therapeutic benefits for various degenerative diseases. The primary aim of this study is to explore approaches for enhancing ovarian function and serum reproductive hormones through the administration of CBP in a murine model. Initially, hUCB was utilized to obtain CBP (CBP), which was subsequently analyzed for cytokine and growth factor profiles in comparison to adult blood plasma (ABP) by use of flow cytometry. Subsequently, POI mouse models were established through the induction of 4-vinylcyclohexene diepoxide, followed by the injection of CBP into the tail. At 7, 14, and 21 days posttreatment, mouse ovaries and blood were collected, and their estrus cycle, body weight, and ovarian weights were evaluated using precise electronic balance. Finally, ovarian morphology and follicle number were assessed through HE staining, while serum levels of anti-Müllerian hormone (AMH), estradiol (E2) and follicle-stimulating hormone (FSH) were determined by ELISA. Our study revealed that individuals with CBP exhibited significantly lower concentrations of proinflammatory cytokines, including IL-ß (p < 0.01) and IL-2 (p < 0.05), while displaying elevated levels of anti-inflammatory cytokines and chemokines, such as IL-2, IL-4, IL-6, IL-8, IL-12P70, IL-17A, IP-10, interferon-γ, and tumor necrosis factor-α (p < 0.01). Furthermore, CBP demonstrated remarkably higher levels of growth factors, including transforming growth factor-ß1, vascular endothelial growth factor, and insulin-like growth factor-1 (p < 0.01) than ABP. Notably, our investigation also revealed that CBP restored the content of serum reproductive hormones, such as AMH, E2, and FSH (p < 0.05), and increased the number of primordial and primary follicles (p < 0.01) and decreased the number of luteal and atretic follicles (p < 0.01) in vivo. Our findings suggested that CBP-secreted cytokines and growth factors could be restored POI ovarian function, enhanced serum reproductive hormones and rescued follicular development in vivo. These findings further support the potential of CBP as a promising strategy in clinical applications for POI related infertility.

Application of metal-organic frameworks in infectious wound healing.

Metal-organic frameworks (MOFs) are metal-organic skeleton compounds composed of self-assembled metal ions or clusters and organic ligands. MOF materials often have porous structures, high specific surface areas, uniform and adjustable pores, high surface activity and easy modification and have a wide range of prospects for application. MOFs have been widely used. In recent years, with the continuous expansion of MOF materials, they have also achieved remarkable results in the field of antimicrobial agents. In this review, the structural composition and synthetic modification of MOF materials are introduced in detail, and the antimicrobial mechanisms and applications of these materials in the healing of infected wounds are described. Moreover, the opportunities and challenges encountered in the development of MOF materials are presented, and we expect that additional MOF materials with high biosafety and efficient antimicrobial capacity will be developed in the future.

Analysis of Clinical Outcome and Prognosis of C-reactive Protein Combined with Albumin in Patients with Acute Myocardial Infarction.

Objective: This study aims to assess the combined predictive value of C-reactive protein (CRP) and albumin (ALB) for major adverse cardiovascular events (MACE) post-percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI). Methods: We analyzed data from continuously enrolled AMI patients who underwent emergency PCI at the First Affiliated Hospital of Xinjiang Medical University over six years, employing logistic regression to derive a predictive equation for in-hospital mortality and out-of-hospital MACE events. Primary endpoints: In-hospital death and out-of-hospital major adverse cardiovascular events. The patients were followed up for 1, 3, 6, and 12 months after discharge. The average follow-up time was 41 months. Results: Among the 601 patients studied, we observed 16 in-hospital deaths and 131 out-of-hospital MACE events. Multivariate logistic regression analysis showed that the independent predictors of out-of-hospital MACE events were age (OR=1.067, 95% CI 1.013-1.124, P = .028), C-reactive protein (OR=1.012, 95% CI 1.000-1.025, P = .045) and albumin (OR=0.874, 95% CI 0.785-0.973, P = .014). Our multivariate logistic regression analysis identified age, CRP, and albumin as independent predictors, with the combined equation yielding an ROC curve area of 0.85, effectively stratifying patients into high-risk and low-risk groups. Subsequent follow-up results validated this risk stratification approach. Conclusion: The study underscores the efficacy of combining CRP and albumin levels as a predictive measure for in-hospital death and out-of-hospital MACE events in AMI patients post-PCI.

Quantum Oscillations in Graphene Using Surface Acoustic Wave Resonators.

Surface acoustic waves (SAWs) provide a contactless method for measuring wave-vector-dependent conductivity. This technique has been used to discover emergent length scales in the fractional quantum Hall regime of traditional, semiconductor-based heterostructures. SAWs would appear to be an ideal match for van der Waals heterostructures, but the right combination of substrate and experimental geometry to allow access to the quantum transport regime has not yet been found. We demonstrate that SAW resonant cavities fabricated on LiNbO_{3} substrates can be used to access the quantum Hall regime of high-mobility, hexagonal boron nitride encapsulated, graphene heterostructures. Our work establishes SAW resonant cavities as a viable platform for performing contactless conductivity measurements in the quantum transport regime of van der Waals materials.