Tunable quantum criticalities in an isospin extended Hubbard model simulator.

Studying strong electron correlations has been an essential driving force for pushing the frontiers of condensed matter physics. In particular, in the vicinity of correlation-driven quantum phase transitions (QPTs), quantum critical fluctuations of multiple degrees of freedom facilitate exotic many-body states and quantum critical behaviours beyond Landau's framework1. Recently, moiré heterostructures of van der Waals materials have been demonstrated as highly tunable quantum platforms for exploring fascinating, strongly correlated quantum physics2-22. Here we report the observation of tunable quantum criticalities in an experimental simulator of the extended Hubbard model with spin-valley isospins arising in chiral-stacked twisted double bilayer graphene (cTDBG). Scaling analysis shows a quantum two-stage criticality manifesting two distinct quantum critical points as the generalized Wigner crystal transits to a Fermi liquid by varying the displacement field, suggesting the emergence of a critical intermediate phase. The quantum two-stage criticality evolves into a quantum pseudo criticality as a high parallel magnetic field is applied. In such a pseudo criticality, we find that the quantum critical scaling is only valid above a critical temperature, indicating a weak first-order QPT therein. Our results demonstrate a highly tunable solid-state simulator with intricate interplay of multiple degrees of freedom for exploring exotic quantum critical states and behaviours.

On-device phase engineering.

In situ tailoring of two-dimensional materials' phases under external stimulus facilitates the manipulation of their properties for electronic, quantum and energy applications. However, current methods are mainly limited to the transitions among phases with unchanged chemical stoichiometry. Here we propose on-device phase engineering that allows us to realize various lattice phases with distinct chemical stoichiometries. Using palladium and selenide as a model system, we show that a PdSe2 channel with prepatterned Pd electrodes can be transformed into Pd17Se15 and Pd4Se by thermally tailoring the chemical composition ratio of the channel. Different phase configurations can be obtained by precisely controlling the thickness and spacing of the electrodes. The device can be thus engineered to implement versatile functions in situ, such as exhibiting superconducting behaviour and achieving ultralow-contact resistance, as well as customizing the synthesis of electrocatalysts. The proposed on-device phase engineering approach exhibits a universal mechanism and can be expanded to 29 element combinations between a metal and chalcogen. Our work highlights on-device phase engineering as a promising research approach through which to exploit fundamental properties as well as their applications.

Effect of plasma exosome lncRNA on isoproterenol hydrochloride-induced cardiotoxicity in rats.

Isoprenaline hydrochloride (IH) is a ß-adrenergic receptor agonist commonly used in the treatment of hypotension, shock, asthma, and other diseases. However, IH-induced cardiotoxicity limits its application. A large number of studies have shown that long noncoding RNA (lncRNA) regulates the occurrence and development of cardiovascular diseases. This study aimed to investigate whether abnormal lncRNA expression is involved in IH-mediated cardiotoxicity. First, the Sprague-Dawley (SD) rat myocardial injury model was established. Circulating exosomes were extracted from the plasma of rats and identified. In total, 108 differentially expressed (DE) lncRNAs and 150 DE mRNAs were identified by sequencing. These results indicate that these lncRNAs and mRNAs are substantially involved in chemical cardiotoxicity. Further signaling pathway and functional studies indicated that lncRNAs and mRNAs regulate several biological processes, such as selective mRNA splicing through spliceosomes, participate in sphingolipid metabolic pathways, and play a certain role in the circulatory system. Finally, we obtained 3 upregulated lncRNAs through reverse transcription-quantitative PCR (RT-qPCR) verification and selected target lncRNA-mRNA pairs according to the regulatory relationship of lncRNA/mRNA, some of which were associated with myocardial injury. This study provides valuable insights into the role of lncRNAs as novel biomarkers of chemical-induced cardiotoxicity.

Multilayer Adsorption Characteristics of CO2 in Organic Nanopores with Different Pore Sizes: Molecular Simulation and Ono-Kondo Lattice Model.

Shale contains numerous organic micropores with significant potential for CO2 storage. To precisely evaluate the CO2 storage potential of shale reservoirs, it is essential to accurately quantify the adsorption of CO2 within these pores. This study used Grand Canonical Monte Carlo (GCMC) molecular simulations to analyze the CO2 adsorption behavior in organic micropores of varying sizes. The study clarified the number and width of the CO2 adsorption layers in micropores of various sizes and proposed a method for segmenting the multilayer adsorption structure. Additionally, the classic Ono-Kondo lattice (OK) model was extended to characterize pore-filling adsorption, incorporating solid-gas and gas-gas interactions. Accurate characterization of CO2 multilayer adsorption and precise calculation of CO2 absolute adsorption in micropores were achieved. Results indicate that CO2 exhibits pore-filling adsorption behavior in organic micropores, forming a multilayer adsorption structure governed by the pore size. Following symmetry principles, the adsorption layer structure in organic micropores can be simplified to a maximum of three layers. When only one adsorption layer forms, its width equals the gas-accessible pore size. For two or more layers, the width of the original layer stabilizes as additional layers form. The stable adsorption layer widths, from nearest to farthest from the pore wall, are 0.33, 0.45, and 0.39 nm. The improved OK model accurately describes CO2 excess and absolute adsorption isotherms across different pore sizes and calculates the CO2 density in each adsorption layer, showing high consistency with GCMC simulation results. These findings highlight the importance of understanding the CO2 multilayer adsorption structure for accurately estimating CO2 adsorption in organic micropores.

Highly Stable HfO2 Memristors through van der Waals Electrode Lamination and Delamination.

Memristors have attracted considerable attention in the past decade, holding great promise for future neuromorphic computing. However, the intrinsic poor stability and large device variability remain key limitations for practical application. Here, we report a simple method to directly visualize the origin of poor stability. By mechanically removing the top electrodes of memristors operated at different states (such as SET or RESET), the memristive layer could be exposed and directly characterized through conductive atomic force microscopy, providing two-dimensional area information within memristors. Based on this technique, we observed the existence of multiple conducting filaments during the formation process and built up a physical model between filament numbers and the cycle-to-cycle variation. Furthermore, by improving the interface quality through the van der Waals top electrode, we could reduce the filament number down to a single filament during all switching cycles, leading to much controlled switching behavior and reliable device operation.

Mutational landscape of DNA damage response deficiency-related genes and its association with immune biomarkers in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) has limited effective treatment strategies. DNA damage response (DDR) genes are of therapeutic interest in multiple cancer types. This study aimed to depict the landscape of DDR mutations in ESCC and evaluate the association between DDR mutations and known immunotherapy biomarkers. We recruited 250 Chinese patients with ESCC and performed next-generation sequencing. A total of 107 patients underwent a PD-L1 examination. Among the 250 patients, 73 (29.2%) harbored at least one DDR gene mutation and were defined as DDR-mut. Among the six functional DDR pathways, homologous recombination (HR) accounted for 12.4% (31/250). DDR-mut patients were significantly associated with higher tumor mutational burden than those in the DDR-wt group (p=7.4e-07). Patients with PDL1-H accounted for 21.2% (36/107) of the patients. PDL1-H was more prevalent in DDR-mut than DDR-wt, although the p-value did not reach a significant level (40.5% vs. 30%, p=0.29). Further analysis revealed that BRCA1, one of the most frequently mutated genes in the HR pathway, was significantly associated with PDL1-H (p=0.01). Our data revealed a subset of patients with ESCC harbored DDR gene mutations. Patients with these DDR gene mutations are significantly associated with immune biomarkers, implying the potential feasibility of combining DDR agents with immunotherapy in patients with DDR deficiency.

Pectus excavatum, kyphoscoliosis associated with thoracolumbar spinal stenosis: a rare case report and literature review.

BACKGROUND: Pectus excavatum is the most common congenital chest wall defect. Thoracolumbar spinal stenosis and kyphoscoliosis was seen in patients with pectus excavatum. It can be caused by ossification of the ligamentum flavum, which is rare in patients with pectus excavatum. CASE PRESENTATION: We reported a 26-year-old woman presented bilateral lower extremities weakness and numbness for two months, progressive worsening. She was diagnosed as thoracolumbar spinal stenosis with ossification of the ligamentum flavum, thoracolumbar kyphoscoliosis associated with pectus excavatum. The posterior instrumentation, decompression with laminectomy, and de-kyposis procedure with multilevel ponte osteotomy were performed. Her postoperative course was uneventful and followed up regularly. Good neurologic symptoms improvement and spinal alignment were achieved. CONCLUSIONS: Pectus excavatum, kyphoscoliosis associated with thoracolumbar spinal stenosis is rare, and thus her treatment options are very challengeable. Extensive laminectomy decompression and de-kyphosis procedures can achieve good improvement of neurologic impingement and spinal alignment.

The Learning Curve and Importance of Collaboration in Endoscopic Thyroidectomy Via Breast Areola Approach: A Single Surgical Team's Experience of 100 Patients.

BACKGROUND: Endoscopic thyroidectomy is popular among young patients because of its excellent cosmetic outcomes. But it takes a long time to become proficient and competent for surgeons. In addition, collaboration plays a critical role in endoscopic thyroidectomy. Our research aims to evaluate the learning curve of endoscopic thyroidectomy via breast areola approach, provide details of this approach, and demonstrate the importance of collaboration. METHODS: The authors retrospectively analyzed 100 cases of benign and malignant thyroid disease who underwent endoscopic thyroidectomy via breast areola approach between January 2015 and December 2020, which were performed by the same group of surgeons with little experience of endoscopic thyroidectomy. The learning curve was analyzed by moving average method. The mean operation time, blood loss, tumor size, postoperative complications were used to determine learning curve progression. RESULTS: The learning curve in the first 30 cases were uplifted, stable at 30 to 60 cases and declined in the following cases. The mean operation time and blood loss decreased significant after the first 30 cases and again after the first 60 cases. And there was no difference in postoperative complications. CONCLUSIONS: A well-trained surgeon with experience in conventional open thyroidectomy can significantly reduce the total operation time by studying the learning curve. The key steps including establishment of working space and reaching for recurrent laryngeal nerve. A stable level can be achieved after 30 cases. More than 60 cases are required to become proficient. A successful endoscopic thyroid surgery requires a stable team.

PDL1-positive exosomes suppress antitumor immunity by inducing tumor-specific CD8+ T cell exhaustion during metastasis.

Metastasis is the main cause of death in individuals with cancer. Immune checkpoint blockade (ICB) can potentially reverse CD8+ cytotoxic T lymphocytes (CTLs) dysfunction, leading to significant remission in multiple cancers. However, the mechanism underlying the development of CTL exhaustion during metastatic progression remains unclear. Here, we established an experimental pulmonary metastasis model with melanoma cells and discovered a critical role for melanoma-released exosomes in metastasis. Using genetic knockdown of nSMase2 and Rab27a, 2 key enzymes for exosome secretion, we showed that high levels of effector-like tumor-specific CD8+ T cells with transitory exhaustion, instead of terminal exhaustion, were observed in mice without exosomes; these cells showed limited inhibitory receptors and strong proliferation and cytotoxicity. Mechanistically, the immunosuppression of exosomes depends on exogenous PD-L1, which can be largely rescued by pretreatment with antibody blockade. Notably, we also found that exosomal PD-L1 acts as a promising predictive biomarker for ICB therapies during metastasis. Together, our findings suggest that exosomal PD-L1 may be a potential immunotherapy target, suggesting a new curative therapy for tumor metastasis.

MicroRNA-194 inhibits PRC1 activation of the Wnt/ß-catenin signaling pathway to prevent tumorigenesis by elevating self-renewal of non-side population cells and side population cells in esophageal cancer stem cells.

Esophageal cancer (EC) is a leading cause of cancer-related deaths worldwide. Recent studies highlight roles for microRNAs (miRNAs) in EC. Microarray analysis identified miR-194 as downregulated in EC. However, little is known about the role of miR-194 in regulating self-renewal or other biological properties of EC stem cells. RT-qPCR and Western blot confirmed the downregulation of miR-194 in EC stem cells and revealed the upregulation of protein regulator of cytokinesis 1 (PRC1) in EC. Dual-luciferase reporter assay confirmed miR-194 targeting of PRC1 resulting in its downregulation. MiR-194 overexpression or PRC1 silencing reduced PRC1 expression, preventing the activation of the Wnt/ß-catenin signaling pathway. Inhibition of the Wnt/ß-catenin signaling pathway prevented the proliferation, invasion, and self-renewal of EC stem cells while promoting apoptosis. Furthermore, overexpressing miR-194 or silencing PRC1 in nude mice decreased the tumor formation ability of EC stem cells in vivo. Taken together, miR-194 prevents the progression of EC by downregulating PRC1 and inactivating the Wnt/ß-catenin signaling pathway.

Observation of Negative Terahertz Photoconductivity in Large Area Type-II Dirac Semimetal PtTe_{2}.

As a newly emergent type-II Dirac semimetal, platinum telluride (PtTe_{2}) stands out from other two dimensional noble-transition-metal dichalcogenides for the unique band structure and novel physical properties, and has been studied extensively. However, the ultrafast response of low energy quasiparticle excitation in terahertz frequency remains nearly unexplored yet. Herein, we employ optical pump-terahertz probe (OPTP) spectroscopy to systematically study the photocarrier dynamics of PtTe_{2} thin films with varying pump fluence, temperature, and film thickness. Upon photoexcitation the terahertz photoconductivity (PC) of PtTe_{2} films shows abrupt increase initially, while the terahertz PC changes into negative value in a subpicosecond timescale, followed by a prolonged recovery process that lasted a few nanoseconds. The magnitude of both positive and negative terahertz PC response shows strongly pump fluence dependence. We assign the unusual negative terahertz PC to the formation of small polaron due to the strong electron-phonon (e-ph) coupling, which is further substantiated by temperature and film thickness dependent measurements. Moreover, our investigations give a subpicosecond timescale of simultaneous carrier cooling and polaron formation. The present study provides deep insights into the underlying dynamics evolution mechanisms of photocarrier in type-II Dirac semimetal upon photoexcitation, which is of crucial importance for designing PtTe_{2}-based optoelectronic devices.

Exploration of irradiation intensity dependent external in-band quantum yield for ZnO and CuO/ZnO photocatalysts.

Decorating metal oxides with wide band-gap semiconductor nano-particles constitute an important approach for synthesizing nano-photocatalysts, where the photocatalytic activity is attributed to the band diagram related effective charge separation and external in-band quantum yield (EIQY). However, up to now, the correlation between the irradiation intensity and the functionalization of the in-band quantum yield has not yet been explained. In this work, by investigating the photocatalytic activity of ZnO and CuO/ZnO (CZO) nano-photocatalysts under various irradiative intensities, we show that the effective charge separation in the CuO/ZnO band alignment is sensitive to weak illumination, while ZnO exhibits a competitive photocatalytic activity with CZO under strong illumination. As a consequence, by modifying the irradiation intensity, the intrinsic ZnO can achieve a similar photocatalytic activity to that of metal oxide decorated ZnO. Besides, the optimal photocatalytic activity of CZO is found to be reachable by manipulating the pollutant concentration.

Terpenoids from the Marine-Derived Fungus Aspergillus sp. RR-YLW-12, Associated with the Red Alga Rhodomela confervoides.

Two new meroterpenoids, aspermeroterpenes D and E (1 and 2), two new ophiobolin-type sesterterpenoids, the C-18 epimers of 18,19-dihydro-18-methoxy-19-hydroxyophiobolin P (6 and 7), and two new drimane-type sesquiterpenoids, 3S-hydroxystrobilactone A (8) and 6-epi-strobilactone A (9), along with 11 known terpenoids (3-5 and 10-17) were isolated from the cultures of the algicolous fungus Aspergillus sp. RR-YLW-12, derived from the red alga Rhodomela confervoides. The structures and relative configurations of new compounds were established by detailed spectroscopic analysis of NMR and HRMS experiments, and the absolute configurations were assigned by X-ray diffraction experiments and comparison of their experimental and calculated ECD spectra. Compound 1 features a rare 6/6/6/6/5 pentacyclic system with a meroterpenoid skeleton, and the structure of terretonin E (3) was revised in this study. Compound 4 showed significant inhibitory activities against three microalgae, Prorocentrum donghaiense, Heterosigma akashiwo, and Chattonella marina, with IC50 values of 10.5, 5.2, and 3.1 µg/mL, respectively.

Long-term results after the one-stage posterior-only surgical correction of thoraco-lumbar kyphoscoliosis in congenital spine deformity caused by two ipsilateral hemi-vertebrae.

BACKGROUND: Two ipsilateral hemivertebrae is less common and presents severe growth imbalance caused by the vertebral anomalies. However, there is a paucity of reports regarding to two ipsilateral thoracolumbar hemivertebrae. The purpose of present study is to evaluate the long-term outcomes of the posterior surgical correction of thoraco-lumbar spine deformity caused by two ipsilateral hemivertebrae. METHODS: From 2006 to 2014, a total of 14 consecutive pediatric patients with congenital thoraco-lumbar hemivertebrae were treated by posterior excision of hemivertebrae with short segment fusion. The following parameters were measured: coronal major curvature, cranial and caudal compensatory curvature, segmental kyphosis, lumbar lordosis, trunk shift, apical vertebra translation and sagittal vertical axis. These results were compared and evaluated in preoperatively, immediately postoperatively and at the final follow-up. All patients had a minimum of 5 years follow-up. RESULTS: The mean age at surgery was 11.1 ± 4.8 years (2yos to 17yos). The mean follow-up period was 80.2 ± 19.4 months (60mons to 117mons). There was a mean improvement of 74.2% in the coronal major curve from a mean angle of 64.1° before surgery to 15.8° at the final follow-up. The cranial and caudal curves improved of 69.8 and 69.0% from 25.6° to 7.7°, 26.9 to 8.2, respectively. The mean thoraco-lumbar kyphosis was 59.9° before and 13.6° after surgery, 20.8° at the final follow-up. Alignment in the coronal and sagittal plane was either maintained or improved within normal values in all patients. CONCLUSIONS: Good correction and spinal balance can be achieved by posterior-only hemivertebrectomy in patients with thoracolumbar kyphocsoliosis caused by two ipsilateral hemivertebra. The complication of neurological injury is low but a technically demanding procedure. More attention should be paid in residual curve progression after surgery.

Two-staged posterior osteotomy surgery in complex and rigid congenital scoliosis in younger than 10 years old children.

BACKGROUND: Congenital scoliosis caused by failure of multiply vertebral segmentation with concave fused rib or unsegmented bar combined with contralateralhemivertebra is usually rigid and produces enormous asymmetric growth. Fusionless techniques have less advantage and come with some complications. Paucity of data was reported for children with complex congenital scoliosis using two-staged osteotomy surgery. METHODS: From 2006 to 2016, 11 patients less than 10 years old undergoing two staged osteotomy surgery for complex rigid congenital scoliosis were retrospectively reviewed. The analysis included age at initial surgery, second surgery and at the latest follow-up, and complications. Changes in coronal major curve, thoracic kyphosis, lumbar lodorsis, apex vertebra translation, T1-T12 length, T1-S1 length, trunk shift, and SVAwere included in radiological evaluation. RESULTS: In all, the mean follow-up was 72.5 ± 23.8 (42 to 112) months. The mean flexibility of the spine was 17.4 and 17.8 % before two surgeries. The mean age at the initial surgery was 6.6 ± 2.6 (2.5-10) years. The mean fusion level was 4.6 ± 1.3 (2 to 6) segments. The mean scoliosis improved from 67.4° to 23.7° after initial surgery and was 17.4° at the latest follow-up. The average increase of T1-S1 length was 0.92 cm per year. No patients had neurological complications. CONCLUSIONS: Two-staged osteotomy surgery including hemivertebrae resection or Y-shaped osteotomy can achieve good radiological and clinical outcomes without severe complications. This procedure can be an option of treatment for complex congenital scoliosis.

Edge-Epitaxial Growth of InSe Nanowires toward High-Performance Photodetectors.

Semiconducting nanowires offer many opportunities for electronic and optoelectronic device applications due to their unique geometries and physical properties. However, it is challenging to synthesize semiconducting nanowires directly on a SiO2 /Si substrate due to lattice mismatch. Here, a catalysis-free approach is developed to achieve direct synthesis of long and straight InSe nanowires on SiO2 /Si substrates through edge-homoepitaxial growth. Parallel InSe nanowires are achieved further on SiO2 /Si substrates through controlling growth conditions. The underlying growth mechanism is attributed to a selenium self-driven vapor-liquid-solid process, which is distinct from the conventional metal-catalytic vapor-liquid-solid method widely used for growing Si and III-V nanowires. Furthermore, it is demonstrated that the as-grown InSe nanowire-based visible light photodetector simultaneously possesses an extraordinary photoresponsivity of 271 A W-1 , ultrahigh detectivity of 1.57 × 1014 Jones, and a fast response speed of microsecond scale. The excellent performance of the photodetector indicates that as-grown InSe nanowires are promising in future optoelectronic applications. More importantly, the proposed edge-homoepitaxial approach may open up a novel avenue for direct synthesis of semiconducting nanowire arrays on SiO2 /Si substrates.

Effect of Natesto on Reproductive Hormones, Semen Parameters and Hypogonadal Symptoms: A Single Center, Open Label, Single Arm Trial.

PURPOSE: To evaluate the effect of short-acting 4.5% nasal testosterone gel (Natesto) on serum testosterone, gonadotropins, total motile sperm count, health related quality of life and sexual function. MATERIALS AND METHODS: This was a single institution, open label, single arm trial conducted between November 2017 and September 2019 at the University of Miami. Men 18 to 55 years old diagnosed with symptomatic hypogonadism (total testosterone less than 300 ng/dl on 2 occasions) were included. Men with azoospermia, vasectomy or a total motile sperm count less than 5 million were excluded. Enrolled patients were treated with Natesto, a short-acting nasal testosterone (125 µl per nostril, 11.0 mg testosterone per dose, TID) for 6 months. RESULTS: In total, 60 men were enrolled in the study. Of these, 44 and 33 patients were evaluated for testosterone at 3 and 6 months, respectively. A total of 31 patients (90.9%) reached a normal testosterone level (greater than 300 ng/dl) at 6 months. Follicle stimulating hormone and luteinizing hormone levels were maintained within the normal range in 81.8% and 72.7% of patients at 6 months, respectively. Total motile sperm count was maintained with total motile sperm count greater than 5 million over the treatment period in 88.4% of men at 3 months and 93.9% at 6 months. There were statistically significant improvements on International Index of Erectile Function sexual desire and overall satisfaction domains at 6 months. CONCLUSIONS: Natesto appears to increase testosterone while maintaining semen parameters in a majority of men. Natesto has the potential to be a safe and effective treatment for men with functional hypogonadism who wish to preserve semen parameters. Long-term studies beyond 6 months are needed before we can safely prescribe nasal testosterone gel for men interested in fertility.

A robust and efficient aqueous electrochemiluminescence emitter constructed by sulfonate porphyrin-based metal-organic frameworks and its application in ascorbic acid detection.

The robust and strong electrochemiluminescence (ECL) emission of organic emitters in an aqueous solution is crucial for expanding their applications in early diagnosis. Herein, a Zn porphyrin-based metal-organic framework ((Zn)porphMOF) was facilely obtained by chelating Zn(ii)meso-tetra (4-sulfonatophenyl) porphine (Zn-TSPP) with Zn ions, showing substantially enhanced ECL radiation with K2S2O8 as the coreactant via the "reduction-oxidation" route in aqueous media. In contrast with Zn-TSPP, (Zn)porphMOF displayed 22-fold increase in the ECL intensity because of the agglomeration effect. By virtue of the dramatic confinement towards the energy and electron transfer of ascorbic acid (AA) during the ECL process, an ultrasensitive biosensor was developed with a wide linear range (3.77 to 26.4 µM) and ultra-low detection limit of 0.29 µM at 3 times of the signal-to-noise ratio (3S/N). This work offers a feasible avenue to harvest the steady and boosted ECL responses of organic molecules in aqueous media, also greatly expanding the MOF applications in bioanalysis.

A New Fault Feature Extraction Method for Rotating Machinery Based on Multiple Sensors.

During the operation of rotating machinery, the vibration signals measured by sensors are the aliasing signals of various vibration sources, and they contain strong noises. Conventional signal processing methods have difficulty separating the aliasing signals, which causes great difficulties in the condition monitoring and fault diagnosis of the equipment. The principle and method of blind source separation are introduced, and it is pointed out that the blind source separation algorithm is invalid in strong pulse noise environments. In these environments, the vibration signals are first de-noised with the median filter (MF) method and the de-noised signals are separated with an improved joint approximate diagonalization of eigenmatrices (JADE) algorithm. The simulation results found here verify the effectiveness of the proposed method. Finally, the vibration signal of the hybrid rotor is effectively separated by the proposed method. A new separation approach is thus provided for vibration signals in strong pulse noise environments.

Direct Evidence for Charge Compensation-Induced Large Magnetoresistance in Thin WTe2.

Since the discovery of extremely large nonsaturating magnetoresistance (MR) in WTe2, much effort has been devoted to understanding the underlying mechanism, which is still under debate. Here, we explicitly identify the dominant physical origin of the large nonsaturating MR through in situ tuning of the magneto-transport properties in thin WTe2 film. With an electrostatic doping approach, we observed a nonmonotonic gate dependence of the MR. The MR reaches a maximum (10600%) in thin WTe2 film at certain gate voltage where electron and hole concentrations are balanced, indicating that the charge compensation is the dominant mechanism of the observed large MR. Besides, we show that the temperature-dependent magnetoresistance exhibits similar tendency with the carrier mobility when the charge compensation is retained, revealing that distinct scattering mechanisms may be at play for the temperature dependence of magneto-transport properties. Our work would be helpful for understanding mechanism of the large MR in other nonmagnetic materials and offers an avenue for achieving large MR in the nonmagnetic materials with electron-hole pockets.