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1.
Phys Rev Lett ; 132(19): 196801, 2024 May 10.
Article En | MEDLINE | ID: mdl-38804928

Stacking ferroelectricity (SFE) has been discovered in a wide range of van der Waals materials and holds promise for applications, including photovoltaics and high-density memory devices. We show that the microscopic origin of out-of-plane stacking ferroelectric polarization can be generally understood as a consequence of a nontrivial Berry phase borne out of an effective Su-Schrieffer-Heeger model description with broken sublattice symmetry, thus elucidating the quantum-geometric origin of polarization in the extremely nonperiodic bilayer limit. Our theory applies to known stacking ferroelectrics such as bilayer transition-metal dichalcogenides in 3R and T_{d} phases, as well as general AB-stacked honeycomb bilayers with staggered sublattice potential. Our explanatory and self-consistent framework based on the quantum-geometric perspective establishes quantitative understanding of out-of-plane SFE materials beyond symmetry principles.

2.
Ophthalmic Plast Reconstr Surg ; 40(1): e1-e4, 2024.
Article En | MEDLINE | ID: mdl-37552498

A 52-year-old woman presented with a 6-month history of progressive right proptosis associated with intermittent right retrobulbar and facial pain. MRI revealed a heterogeneously enhancing, well-circumscribed, ovoid, soft tissue mass in the intraconal space near the right orbital apex displacing the optic nerve medially. Excisional biopsy established the diagnosis of a schwannoma-perineurioma hybrid peripheral nerve sheath tumor (HPNST). This case represents only the second reported occurrence, to our knowledge, of an orbital schwannoma-perineurioma HPNST.


Exophthalmos , Nerve Sheath Neoplasms , Neurilemmoma , Orbital Neoplasms , Female , Humans , Middle Aged , Orbit/diagnostic imaging , Orbit/pathology , Nerve Sheath Neoplasms/diagnosis , Neurilemmoma/diagnosis , Neurilemmoma/pathology , Orbital Neoplasms/pathology
3.
Mar Pollut Bull ; 196: 115658, 2023 Nov.
Article En | MEDLINE | ID: mdl-37837784

Mangroves are vital components of coastal ecosystems. Due to the complex canopy morphology and dense distribution of mangroves, it is challenging to accurately estimate the density based on satellite data. In this study, a density regression-based mangrove mapping network is proposed. The network can capture the multi-scale characteristics of mangroves through the combination of an attention mechanism and a parallel segmentation path, and its performance is better than existing methods. We then apply it to mapping the Greater Bay Area (GBA) the number of mangrove trees. The results show about 2.55 million mangrove trees in the GBA, with an average density of 782 trees per hectare. The tree number of mangroves on the beach is significantly higher than those distributed along the riverbank. This study is the first to achieve mangrove tree count mapping, opening up new prospects for applying satellite-based mangrove monitoring.


Ecosystem , Trees , Hong Kong , Macau , Conservation of Natural Resources
4.
Chem Sci ; 14(27): 7589-7594, 2023 Jul 12.
Article En | MEDLINE | ID: mdl-37449068

Magnetization is a common measurable for characterizing bulk, nanoscale, and molecular materials, which can be quantified to high precision as a function of an applied external field. These data provide detailed information about a material's electronic structure, phase purity, and impurities, though interpreting this data can be challenging due to many contributing factors. In sub-single-domain particles of a magnetic material, an inherently time-dependent rotation of the entire particle spin becomes possible. This phenomenon, known as superparamagnetism (SPM), simultaneously represents a very early size-dependent property to be considered, while being one of the least explored in the current quantum materials era. This discrepancy is, at least in part, due to the need for models with less built-in complexity that can facilitate the generation of comparative data. In this work, we map an extensive dataset of variable-size SPM Fe3O4 (magnetite) to an intrinsic statistical model for their field-dependence. By constraining the SPM behavior to a probabilistic model, the data are apportioned to several decorrelated sources. From this, there is strong evidence that standard measures such as saturation magnetization, MS, are poor comparative parameters, being dependent on experimental knowledge and measurement of the magnetic mass. In contrast, parameters of the intrinsic probability distribution, such as the maximum susceptibility, χmax, are far better suited to describe the SPM behavior itself and do not propagate unknown magnetic mass error. By confining the data fitting to intrinsic variables of the model distribution, scaling parameters, and linear contributions, we find greater value in magnetic data, ultimately aiding potential synthesis diagnostics and prediction of new properties and functionality.

5.
Graefes Arch Clin Exp Ophthalmol ; 261(7): 2081-2088, 2023 Jul.
Article En | MEDLINE | ID: mdl-36752841

PURPOSE: This study aims to investigate trends and risk factors associated with work-related ocular injuries occurring in adults aged 19-64 using the National Trauma Databank (NTDB). METHODS: In this retrospective, cross-sectional study, the NTDB was used to collect all patients with an ICD-9 code of work-related ocular trauma from 2007 to 2014. Demographic data and risk factors collected included age, gender, race, setting, machinery, and mechanism. Descriptive statistics, univariate, and logistic regression multivariate analyses were conducted. RESULTS: Between 2007 and 2014, 234,983 cases of work-related trauma were identified, of which 11,097 (5.7%) cases involved ocular trauma. The mean age of patients was 40.7 years (SD = 12.2), and the majority of patients (93.7%) were male. Most injuries occurred in an industrial facility, and the most common injuries were orbital floor fractures (OFFs), ocular contusions, open wounds to the adnexa, and open globe injuries (OGIs). OFFs most commonly involved a concurrent fracture of another facial or skull bone. Male gender (RR = 1.22; CI 1.09-1.38), accidental falls (RR = 1.50; CI 1.41-1.60), trauma from falling objects (RR = 1.34; CI 1.21-1.48), involvement in an unarmed fight (RR = 1.63; CI 1.39-1.91), assault by a blunt object (RR = 1.59; CI 1.31-1.91), and injury caused by animals (RR = 1.63; CI 1.30-2.02) were risk factors for OFFs. Patients with OFFs were less likely to have a concurrent OGI (RR = 0.27; CI 0.23-0.32). On the other hand, injuries occurring in industrial facilities (RR = 1.29; CI 1.11-1.51) and injuries with a loose foreign body striking the eye or adnexa (RR = 1.54; CI 1.28-1.84) were risk factors for OGI. The most common causes of work-related ocular trauma were accidental falls, motor vehicle accidents, and accidentally being struck in the eye. The mean length of hospital stay was 6.56 days (SD = 10.82); 36.7% of patients required ICU admission, and the overall in-hospital mortality rate was 2.8%. CONCLUSION: The majority of work-related ocular trauma occurred in men, most commonly in industrial locations. Accidental falls were the most common identified cause of trauma. OFF was the most common ocular injury; 80% of OFF cases involved additional facial and skull fractures. Patients with OFFs were less likely to have a concurrent OGI compared with patients without OFFs.


Eye Injuries , Orbital Fractures , Male , Female , United States/epidemiology , Humans , Retrospective Studies , Cross-Sectional Studies , Age Distribution , Eye Injuries/epidemiology , Eye Injuries/etiology , Risk Factors , Orbital Fractures/etiology , Orbital Fractures/complications
7.
mLife ; 2(3): 239-252, 2023 Sep.
Article En | MEDLINE | ID: mdl-38817815

Disentangling the assembly mechanisms controlling community composition, structure, distribution, functions, and dynamics is a central issue in ecology. Although various approaches have been proposed to examine community assembly mechanisms, quantitative characterization is challenging, particularly in microbial ecology. Here, we present a novel approach for quantitatively delineating community assembly mechanisms by combining the consumer-resource model with a neutral model in stochastic differential equations. Using time-series data from anaerobic bioreactors that target microbial 16S rRNA genes, we tested the applicability of three ecological models: the consumer-resource model, the neutral model, and the combined model. Our results revealed that model performances varied substantially as a function of population abundance and/or process conditions. The combined model performed best for abundant taxa in the treatment bioreactors where process conditions were manipulated. In contrast, the neutral model showed the best performance for rare taxa. Our analysis further indicated that immigration rates decreased with taxa abundance and competitions between taxa were strongly correlated with phylogeny, but within a certain phylogenetic distance only. The determinism underlying taxa and community dynamics were quantitatively assessed, showing greater determinism in the treatment bioreactors that aligned with the subsequent abnormal system functioning. Given its mechanistic basis, the framework developed here is expected to be potentially applicable beyond microbial ecology.

8.
Orbit ; : 1-5, 2022 Dec 05.
Article En | MEDLINE | ID: mdl-36469586

A 5-year-old girl presented with a 6-month history of strabismus and painless left proptosis. Magnetic resonance imaging revealed a homogenously enhancing, anterior, superomedial, left orbital mass. Excisional biopsy established the diagnosis of orbital glomangiopericytoma. Glomangiopericytoma of soft tissue is a perivascular myoid neoplasm with hemangiocytoma-like vascular channels that has overlapping features between glomus tumor and myopericytoma. To the authors' knowledge, glomangiopericytoma of the orbit has not previously been reported.

9.
Pain Physician ; 25(8): E1174-E1182, 2022 11.
Article En | MEDLINE | ID: mdl-36375184

BACKGROUND: Amputees commonly feel an intermittent tingling, piercing, or burning sensation in the region of the missing portion of the amputated limb, a phenomenon known as phantom limb pain. Current treatment modalities include medications, mirror therapy, transcutaneous electrical nerve stimulation, and more recently neuromodulation through spinal cord stimulation and dorsal root ganglion (DRG) stimulation. OBJECTIVES: The aim of this review is to examine the existing literature to identify and analyze evidence for the use of DRG stimulation as a pain relief modality for phantom limb pain. STUDY DESIGN: Scoping Review. METHODS: A literature search was conducted using relevant search terms. PubMed, Web of Science, Cochrane, and CINAHL databases were used, and reference lists of selected articles were searched for additional relevant literature. RESULTS: Most studies analyzed had low to moderate bias in all categories assessed. There are case reports and case series indicating that DRG stimulation could be an effective treatment method for phantom limb pain. Fifteen of 25 patients across 5 studies achieved satisfactory levels of pain relief and significant improvements were reported by all patients evaluated for quality of life. Patient selection and proper targeting of stimulation are important factors in limiting large variability in results while determining effectiveness of this pain relief modality. LIMITATIONS: The studies included in this scoping review are limited by the number of cases and by the length of follow-up. Also, there are no randomized control trials or observational studies with large sample sizes that allow for adequate power. Many of these studies do not have a standardized methodology of quantifying pain relief from DRG stimulation. CONCLUSIONS: The cumulative evidence at present suggests DRG stimulation may be a potentially effective treatment for phantom limb pain, however, a powered prospective randomized controlled trial is needed to assess the long-term benefits of this treatment modality. Given the increasing population of military veterans who are living with limb amputations, finding a modality for adequate long-term pain control is crucial.


Phantom Limb , Spinal Cord Stimulation , Humans , Phantom Limb/therapy , Ganglia, Spinal/physiology , Quality of Life , Prospective Studies , Spinal Cord Stimulation/methods , Paresthesia
10.
Chem Mater ; 34(17): 8043-8053, 2022 Sep 13.
Article En | MEDLINE | ID: mdl-36117881

The synthesis of iron oxide nanoparticles with control over size and shape has long been an area of research, with iron oleate being arguably the most successful precursor. Issues with reproducibility and versatility in iron oleate-based syntheses remain, however, in large part due to the mutable nature of its structure and stoichiometry. In this work, we characterize two new forms of iron oleate precursor that can be isolated in large quantities, show long-term stability, and have well-defined stoichiometry, leading to reproducible and predictable reactivity. Synthesis with these precursors is shown to produce iron oxide nanoparticles in a tunable size range of 4-16 nm with low size dispersity and properties consistent with magnetite in the superparamagnetic size regime.

11.
Ann Plast Surg ; 88(3 Suppl 3): S266-S273, 2022 05 01.
Article En | MEDLINE | ID: mdl-35180750

INTRODUCTION: Since 1999, nearly 841,000 individuals have died from overdoses, 29% involving prescription opioids. Use of opioids for postoperative pain lacks evidence-based guidelines, and despite studies showing the efficacy of nonopioid agents in reducing postoperative morbidity, opioids are still routinely prescribed. However, multiple states are adopting prescription drug monitoring programs and prescription drug laws. The authors sought to investigate recent opioid prescription patterns among plastic surgeons. METHODS: This cross-sectional study used "Medicare Provider Utilization and Payment Data: Part D Prescriber" provided by the Centers for Medicare & Medicaid Services from 2016 to 2018. Entries were filtered to include plastic surgeons. Demographic variables included surgeon sex, geographic region and state, board certification status, and length of experience. The surgeon's practice was designated as academic, private, or both. Outcomes included total opioid claims, opioid prescriber rate, and days per claim. Kruskal-Wallis tests were used for statistical comparison (α = .05). RESULTS: From 2016 to 2018, plastic surgeons wrote 289,525 opioid prescriptions for 1,729,523 days (6.0 days per prescription), totaling $3,346,979.39. In 2018, 62.2% of plastic surgeons prescribed 0 to 10 opioids, 36.5% prescribed 11 to 50 opioids, and 1.3% prescribed more than 50. Furthermore, 99.5% of plastic surgeons prescribing opioids are practicing in metropolitan areas (rural-urban commuting area codes 1-3). Plastic surgeons who were male or were board certified had significantly lower opioid prescriber rates (P < 0.001). There were no significant variations in outcomes by length of surgeon experience. Geographic region was significantly associated with opioid prescription rates and days per claim, with Southern plastic surgeons having lower rates (P < 0.001) and those Northeastern ones prescribing shorter courses (P = 0.004). The number of opioid claims, days per claim, and opioid prescriber rates were all significantly lower in 2018 than in 2017 and 2016 (P < 0.001). CONCLUSIONS: Prescriptions written by plastic surgeons may have contributed to the opioid epidemic, but 2018 data suggest opioids are becoming less routine in postoperative pain control. Further studies are warranted to assess factors related to reduced and shorter opioid prescriptions by plastic surgeons in the South and Northeast, respectively. Such insight, if adopted into law and implemented into clinical practice, may help reduce the burden of the opioid epidemic.


Medicare Part D , Surgery, Plastic , Aged , Analgesics, Opioid/therapeutic use , Cross-Sectional Studies , Female , Humans , Male , Pain, Postoperative/drug therapy , Practice Patterns, Physicians' , Prescriptions , United States
12.
Proc Natl Acad Sci U S A ; 119(2)2022 01 11.
Article En | MEDLINE | ID: mdl-34992138

Networks are vital tools for understanding and modeling interactions in complex systems in science and engineering, and direct and indirect interactions are pervasive in all types of networks. However, quantitatively disentangling direct and indirect relationships in networks remains a formidable task. Here, we present a framework, called iDIRECT (Inference of Direct and Indirect Relationships with Effective Copula-based Transitivity), for quantitatively inferring direct dependencies in association networks. Using copula-based transitivity, iDIRECT eliminates/ameliorates several challenging mathematical problems, including ill-conditioning, self-looping, and interaction strength overflow. With simulation data as benchmark examples, iDIRECT showed high prediction accuracies. Application of iDIRECT to reconstruct gene regulatory networks in Escherichia coli also revealed considerably higher prediction power than the best-performing approaches in the DREAM5 (Dialogue on Reverse Engineering Assessment and Methods project, #5) Network Inference Challenge. In addition, applying iDIRECT to highly diverse grassland soil microbial communities in response to climate warming showed that the iDIRECT-processed networks were significantly different from the original networks, with considerably fewer nodes, links, and connectivity, but higher relative modularity. Further analysis revealed that the iDIRECT-processed network was more complex under warming than the control and more robust to both random and target species removal (P < 0.001). As a general approach, iDIRECT has great advantages for network inference, and it should be widely applicable to infer direct relationships in association networks across diverse disciplines in science and engineering.

13.
J Acad Ophthalmol (2017) ; 14(1): e133-e140, 2022 Jan.
Article En | MEDLINE | ID: mdl-37388483

Importance San Francisco Match publishes no data on the research output of matched applicants to an ophthalmology residency. Objective The aim of this study was to examine the temporal trends in publication volume by medical students who successfully matched into a top ophthalmology residency. Methods This retrospective case series compared all residents in the top 30 ophthalmology residency programs from the class of 2022 and 2017. Publication volume from before September 15th of the residents' fourth year of medical school was recorded using PubMed and Google Scholar. We recorded total number of publications (any authorship), first/second author publications, and ophthalmology-specific publications. Using Welch's t -test, publication volumes were statistically compared against all others. Results One-hundred sixty-one residents from the class of 2022 and 145 residents from the class of 2017 were included. Total publications per matched applicant (mean ± standard deviation) were 3.04 ± 0.35 for the class of 2022 and 1.67 ± 0.23 for the class of 2017. Mean publications in ophthalmology journals were 1.07 ± 0.20 (2022) and 0.58 ± 0.13 (2017); mean first author publications were 1.00 ± 0.13 (2022) and 0.64 ± 0.11 (2017) and mean second author publications were 0.70 ± 0.10 (2022) and 0.37 ± 0.06 (2017). Research productivity in all four metrics (total, ophthalmology journals, first author, and second author publications) was significantly higher for the class of 2022 than the class of 2017 ( p = 0.001; p = 0.03; p = 0.03; p = 0.02, respectively) supporting the trend of increasing research output among students. Applicants with PhD degrees had statistically more total and first author publications in 2017 ( p = 0.01; p = 0.045), but only more first author publications in 2022 ( p = 0.01). International applicants produced significantly more total publications in 2022 ( p < 0.001). Conclusions Overall, after a 5-year period, the authors found matched applicants had significantly increased publications compared with those at the beginning of the period. We also identified several applicant factors that may have variable effects on research publication. This analysis emphasizes the growing importance of research in the match process and can help future applicants navigate the ophthalmology match.

14.
J Curr Glaucoma Pract ; 16(3): 205-207, 2022.
Article En | MEDLINE | ID: mdl-36793260

Aim: To report a case of uveitis-glaucoma-hyphema (UGH) syndrome secondary to a tilted toric intraocular lens (IOL). Background: Over the past few decades, upgrades in lens design, surgical techniques, and posterior chamber IOLs have drastically decreased the incidence of UGH syndrome. We present a rare case of UGH syndrome developing 2 years after a seemingly uneventful cataract surgery and its subsequent management. Case description: A 69-year-old female presented with episodes of sudden visual disturbance in her right eye 2 years after a seemingly uneventful cataract surgery with placement of a toric IOL. Workup included ultrasound biomicroscopy (UBM), which revealed a tilted IOL and confirmed haptic-induced iris transillumination defects consistent with the diagnosis of UGH syndrome. The patient underwent surgical repositioning of the IOL, which led to the resolution of UGH. Conclusion: Uuveitis-glaucoma-hyphema developed from a tilted toric IOL inducing posterior iris chaffing. Careful examination and UBM revealed the IOL and haptic out of the bag position, which was critical in determining the underlying UGH mechanism. The surgical intervention led to the resolution of UGH syndrome. Clinical significance: In patients with a history of uneventful cataract surgery who develop UGH-like symptoms, continued examination of implant orientation and haptic position is critical in preventing the need for future procedures. How to cite this article: Zhou B, Bekerman VP, Chu DS, et al. Late Onset Uveitis-glaucoma-hyphema Syndrome with Out-the-bag Placement of Intraocular Lens. J Curr Glaucoma Pract 2022;16(3):205-207.

15.
J Curr Glaucoma Pract ; 16(3): 166-169, 2022.
Article En | MEDLINE | ID: mdl-36793262

Aim: To investigate the long-term efficacy of adjunctive use of latanoprostene bunod (LBN), a new nitric oxide donating prostaglandin medication, in refractory cases of glaucoma at a tertiary care center. Materials and methods: A review for patients who received add-on LBN was conducted from 1st January 2018 to 31st August 2020. A total of 33 patients (53 eyes) met the inclusion criteria of being on ≥3 topical medications, having an intraocular pressure measurement prior to starting LBN, and having adequate follow-up. Baseline demographics, prior treatments, adverse effects, and intraocular pressures measured at baseline, 3, 6, and 12 months were recorded. Results: Mean baseline intraocular pressure (IOP) [mm Hg ± standard deviation (SD)] was 19.9 ± 6.0. At 3 months, 49 eyes had a mean IOP of 17.3 ± 5.5 (p < 0.01) with an absolute reduction of 2.6 ± 6.6 and a percent reduction of 9 ± 28%. At 6 months, 35 eyes had a mean IOP of 17.2 ± 4.7 (p < 0.01) with an absolute reduction of 3.6 ± 7.4 and a percent reduction of 11 ± 30%. At 12 months, 28 eyes had a mean IOP of 16 ± 4.5 (p < 0.01) with an absolute reduction of 5.8 ± 7.4 and a percent reduction of 19 ± 38%. Over the course of the study, 18 eyes were lost to follow-up. Three eyes had a laser trabeculoplasty, and four eyes required incisional surgery. No eyes discontinued the medication due to adverse effects. Conclusion: Adjunctive use of LBN in refractory glaucoma showed clinically and statistically significant IOP reductions at 3, 6, and 12-month time points. IOP reduction in patients was stable throughout the course of the study, with the largest decreases seen at the 12-month interval. Clinical significance: LBN was well tolerated by patients and may be useful as an additive agent in providing long-term intraocular pressure reduction for patients with severe glaucoma on maximal therapy. How to cite this article: Zhou B, Bekerman VP, Khouri AS. Use of Latanoprostene Bunod as Adjunctive Glaucoma Therapy in Refractory Glaucoma. J Curr Glaucoma Pract 2022;16(3):166-169.

16.
J Glaucoma ; 30(3): e40-e46, 2021 03 01.
Article En | MEDLINE | ID: mdl-33337723

PRCIS: Telepresence robots (TR) present the versatility to effectively provide remote educational sessions for patients affected by glaucoma to improve disease knowledge. Given COVID-19's effect on clinical practice, TR can maintain social distancing when educating patients. PURPOSE: TR are devices that allow remote users to have a mobile presence anywhere. We compared the effect of an education session given by an in-person educator versus a TR on glaucoma knowledge and identified factors that impact patient education. METHODS: Eighty-five glaucoma patients were split into control, human, and TR groups. We measured glaucoma knowledge scores (KS) using the National Eye Institute's Eye-Q Test. Human and TR groups had the education session with a human or TR followed by the questionnaire. The control group was administered the questionnaire without an education session. Treatment regimen recall (RR) >90% was considered a success. We used linear regression and binary logistic regression to determine variables that affect KS and RR, respectively. RESULTS: Mean age was 58.3±2.8 years. 49% were female. Mean KS were 5.8±0.7 in the control group (n=31), 7.9±0.5 in the TR group (n=26), and 8.4±0.5 in the human group (n=28). Control participants had a lower mean KS than the human or TR groups (P<0.001). Having the education session (2.5, P<0.001), education greater than high school (0.8, P=0.016), and diabetes (-0.7, P=0.037) affected KS. Having diabetes (odds ratio=0.14, P=0.014) negatively affected RR. Having the education session may affect RR (odds ratio=5.47, P=0.07), warranting additional studies. CONCLUSIONS: Education sessions with a human and TR improved patients' glaucoma KS. TRs may serve as an alternative to in-person education sessions and allow educators to safely and effectively educate patients remotely to adhere to COVID-19 social distancing guidelines.


COVID-19/epidemiology , Glaucoma/therapy , Health Knowledge, Attitudes, Practice , Intraocular Pressure/physiology , Pandemics , Patient Education as Topic/methods , Robotics/instrumentation , Comorbidity , Female , Glaucoma/epidemiology , Glaucoma/physiopathology , Humans , Male , Mental Recall , Middle Aged , SARS-CoV-2 , Surveys and Questionnaires
17.
Phys Rev Lett ; 125(10): 107001, 2020 Sep 04.
Article En | MEDLINE | ID: mdl-32955301

Recent experiments reported gate-induced superconductivity in the monolayer 1T^{'}-WTe_{2} which is a two-dimensional topological insulator in its normal state. The in-plane upper critical field B_{c2} is found to exceed the conventional Pauli paramagnetic limit B_{p} by one to three times. The enhancement cannot be explained by conventional spin-orbit coupling which vanishes due to inversion symmetry. In this Letter, we unveil some distinctive superconducting properties of centrosymmetric 1T^{'}-WTe_{2} which arise from the coupling of spin, momentum and band parity degrees of freedom. As a result of this spin-orbit-parity coupling (SOPC): (i) there is a first-order superconductor-metal transition at B_{c2} that is much higher than the Pauli paramagnetic limit B_{p}, (ii) spin-susceptibility is anisotropic with respect to in-plane directions and can result in possible anisotropic B_{c2}, and (iii) the B_{c2} exhibits a strong gate dependence as the spin-orbit-parity coupling is significant only near the topological band crossing points. The importance of SOPC on the topologically nontrivial inter-orbital pairing phase is also discussed. Our theory generally applies to centrosymmetric materials with topological band inversions.

18.
Nat Commun ; 10(1): 2217, 2019 05 17.
Article En | MEDLINE | ID: mdl-31101813

Cd3As2 is a three-dimensional Dirac semimetal with separated Dirac points in momentum space. In spite of extensive transport and spectroscopic studies on its exotic properties, the evidence of superconductivity in its surface states remains elusive. Here, we report the observation of proximity-induced surface superconductivity in Nb/Cd3As2 hybrid structures. Our four-terminal transport measurement identifies a pronounced proximity-induced pairing gap (gap size comparable to Nb) on the surfaces, which exhibits a flat conductance plateau in differential conductance spectra, consistent with our theoretical simulations. The surface supercurrent from Nb/Cd3As2/Nb junctions is also achieved with a Fraunhofer/SQUID-like pattern under out-of-plane/in-plane magnetic fields, respectively. The resultant mapping shows a predominant distribution on the top and bottom surfaces as the bulk carriers are depleted, which can be regarded as a higher dimensional analog of edge supercurrent in two-dimensional quantum spin Hall insulators. Our study provides the evidence of surface superconductivity in Dirac semimetals.

19.
Nat Commun ; 10(1): 611, 2019 02 05.
Article En | MEDLINE | ID: mdl-30723283

Electrons hopping in two-dimensional honeycomb lattices possess a valley degree of freedom in addition to charge and spin. In the absence of inversion symmetry, these systems were predicted to exhibit opposite Hall effects for electrons from different valleys. Such valley Hall effects have been achieved only by extrinsic means, such as substrate coupling, dual gating, and light illuminating. Here we report the first observation of intrinsic valley Hall transport without any extrinsic symmetry breaking in the non-centrosymmetric monolayer and trilayer MoS2, evidenced by considerable nonlocal resistance that scales cubically with local resistance. Such a hallmark survives even at room temperature with a valley diffusion length at micron scale. By contrast, no valley Hall signal is observed in the centrosymmetric bilayer MoS2. Our work elucidates the topological origin of valley Hall effects and marks a significant step towards the purely electrical control of valley degree of freedom in topological valleytronics.

20.
ACS Cent Sci ; 4(9): 1222-1227, 2018 Sep 26.
Article En | MEDLINE | ID: mdl-30276256

The phenomenon of granular magnetoresistance offers the promise of rapid functional materials discovery and high-sensitivity, low-cost sensing technology. Since its discovery over 25 years ago, a major challenge has been the preparation of solids composed of well-characterized, uniform, nanoscale magnetic domains. Rapid advances in colloidal nanochemistry now facilitate the study of more complex and finely controlled materials, enabling the rigorous exploration of the fundamental nature and maximal capabilities of this intriguing class of spintronic materials. We present the first study of size-dependence in granular magnetoresistance using colloidal nanoparticles. These data demonstrate a strongly nonlinear size-dependent magnetoresistance with smaller particles having strong ΔR/R ∼ 18% at 300 K and larger particles showing a 3-fold decline. Importantly, this indicates that CoFe2O4 can act as an effective room temperature granular magnetoresistor and that neither a high superparamagnetic blocking temperature nor a low overall resistance are determining factors in viable magnetoresistance values for sensing applications. These results demonstrate the promise of wider exploration of nontraditional granular structures composed of nanomaterials, molecule-based magnets, and metal-organic frameworks.

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