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1.
Sci Bull (Beijing) ; 2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38594099

RESUMO

Magnetic impurities in superconductors are of increasing interest due to emergent Yu-Shiba-Rusinov (YSR) states and Majorana zero modes for fault-tolerant quantum computation. However, a direct relationship between the YSR multiple states and magnetic anisotropy splitting of quantum impurity spins remains poorly characterized. By using scanning tunneling microscopy, we systematically resolve individual transition-metal (Fe, Cr, and Ni) impurities induced YSR multiplets as well as their Zeeman effects in the K3C60 superconductor. The YSR multiplets show identical d orbital-like wave functions that are symmetry-mismatched to the threefold K3C60(1 1 1) host surface, breaking point-group symmetries of the spatial distribution of YSR bound states in real space. Remarkably, we identify an unprecedented fermion-parity-preserving quantum phase transition between ground states with opposite signs of the uniaxial magnetic anisotropy that can be manipulated by an external magnetic field. These findings can be readily understood in terms of anisotropy splitting of quantum impurity spins, and thus elucidate the intricate interplay between the magnetic anisotropy and YSR multiplets.

2.
Sci Rep ; 14(1): 6152, 2024 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-38485963

RESUMO

Colonoscopy is one of the main methods to detect colon polyps, and its detection is widely used to prevent and diagnose colon cancer. With the rapid development of computer vision, deep learning-based semantic segmentation methods for colon polyps have been widely researched. However, the accuracy and stability of some methods in colon polyp segmentation tasks show potential for further improvement. In addition, the issue of selecting appropriate sub-models in ensemble learning for the colon polyp segmentation task still needs to be explored. In order to solve the above problems, we first implement the utilization of multi-complementary high-level semantic features through the Multi-Head Control Ensemble. Then, to solve the sub-model selection problem in training, we propose SDBH-PSO Ensemble for sub-model selection and optimization of ensemble weights for different datasets. The experiments were conducted on the public datasets CVC-ClinicDB, Kvasir, CVC-ColonDB, ETIS-LaribPolypDB and PolypGen. The results show that the DET-Former, constructed based on the Multi-Head Control Ensemble and the SDBH-PSO Ensemble, consistently provides improved accuracy across different datasets. Among them, the Multi-Head Control Ensemble demonstrated superior feature fusion capability in the experiments, and the SDBH-PSO Ensemble demonstrated excellent sub-model selection capability. The sub-model selection capabilities of the SDBH-PSO Ensemble will continue to have significant reference value and practical utility as deep learning networks evolve.


Assuntos
Neoplasias do Colo , Pólipos , Humanos , Neoplasias do Colo/diagnóstico por imagem , Colonoscopia , Valores de Referência , Semântica , Processamento de Imagem Assistida por Computador
3.
J Med Imaging (Bellingham) ; 11(2): 024004, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38525292

RESUMO

Purpose: Colon cancer is one of the top three diseases in gastrointestinal cancers, and colon polyps are an important trigger of colon cancer. Early diagnosis and removal of colon polyps can avoid the incidence of colon cancer. Currently, colon polyp removal surgery is mainly based on artificial-intelligence (AI) colonoscopy, supplemented by deep-learning technology to help doctors remove colon polyps. With the development of deep learning, the use of advanced AI technology to assist in medical diagnosis has become mainstream and can maximize the doctor's diagnostic time and help doctors to better formulate medical plans. Approach: We propose a deep-learning model for segmenting colon polyps. The model adopts a dual-branch structure, combines a convolutional neural network (CNN) with a transformer, and replaces ordinary convolution with deeply separable convolution based on ResNet; a stripe pooling module is introduced to obtain more effective information. The aggregated attention module (AAM) is proposed for high-dimensional semantic information, which effectively combines two different structures for the high-dimensional information fusion problem. Deep supervision and multi-scale training are added in the model training process to enhance the learning effect and generalization performance of the model. Results: The experimental results show that the proposed dual-branch structure is significantly better than the single-branch structure, and the model using the AAM has a significant performance improvement over the model not using the AAM. Our model leads 1.1% and 1.5% in mIoU and mDice, respectively, when compared with state-of-the-art models in a fivefold cross-validation on the Kvasir-SEG dataset. Conclusions: We propose and validate a deep learning model for segmenting colon polyps, using a dual-branch network structure. Our results demonstrate the feasibility of complementing traditional CNNs and transformer with each other. And we verified the feasibility of fusing different structures on high-dimensional semantics and successfully retained the high-dimensional information of different structures effectively.

4.
Math Biosci Eng ; 21(1): 1610-1624, 2024 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-38303480

RESUMO

Deep learning technology has shown considerable potential in various domains. However, due to privacy issues associated with medical data, legal and ethical constraints often result in smaller datasets. The limitations of smaller datasets hinder the applicability of deep learning technology in the field of medical image processing. To address this challenge, we proposed the Federated Particle Swarm Optimization algorithm, which is designed to increase the efficiency of decentralized data utilization in federated learning and to protect privacy in model training. To stabilize the federated learning process, we introduced Tri-branch feature pyramid network (TFPNet), a multi-branch structure model. TFPNet mitigates instability during the aggregation model deployment and ensures fast convergence through its multi-branch structure. We conducted experiments on four different public datasets:CVC-ClinicDB, Kvasir, CVC-ColonDB and ETIS-LaribPolypDB. The experimental results show that the Federated Particle Swarm Optimization algorithm outperforms single dataset training and the Federated Averaging algorithm when using independent scattered data, and TFPNet converges faster and achieves superior segmentation accuracy compared to other models.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Privacidade
5.
Complement Ther Clin Pract ; 55: 101828, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38241803

RESUMO

BACKGROUND AND PURPOSE: Post-stroke depression (PSD) has major implications for rehabilitation, motor recovery, activities of daily living, social and interpersonal functioning, and mortality. In view of the side effects of antidepressants, aromatherapy, a widely used non-pharmacological therapy, has received growing attention in recent years for its benefits of reduced complications, accessibility, and effectiveness. This study was designed to assess the effects of inhalation aromatherapy with lavender essential oil on depression and sleep quality in patients with PSD. MATERIALS AND METHODS: Forty patients with PSD were enrolled and randomized into experimental and placebo groups. Experimental-group patients inhaled microencapsulated lavender essential oil every night at bedtime over a period of 4 weeks. A nonwoven bag containing 2.3 g of microcapsules with about 1.5 g of lavender essential oil was placed on or under the patient's pillow, depending on the patient's scent sensitivity. Placebo-group patients used the empty nonwoven bags for the same period as the experimental group. The 17-item Hamilton Rating Scale for Depression (HAMD-17), the Zung Self-Rating Depression Scale (SDS), and the Pittsburgh Sleep Quality Index (PSQI) were used to measure outcomes. RESULTS: The HAMD-17 score, SDS score, and PSQI score showed statistically significant differences between both groups before and after intervention (P ≤ 0.01). The improvement in the experimental group was more marked than in the placebo group (P < 0.05). CONCLUSION: Lavender essential oil inhalation aromatherapy may help reduce depression and improve sleep quality in patients with PSD.


Assuntos
Aromaterapia , Lavandula , Óleos Voláteis , Humanos , Qualidade do Sono , Atividades Cotidianas , Método Simples-Cego , Depressão/tratamento farmacológico , Depressão/etiologia , Óleos Voláteis/uso terapêutico , Óleos de Plantas/uso terapêutico
6.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao ; 45(4): 627-633, 2023 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-37654143

RESUMO

Objective To explore the clinicopathological features and prognosis of the patients newly diagnosed with lung adenocarcinoma with both EGFR mutation and C-MET amplification.Methods The pathological sections were reviewed.EGFR mutation was detected by amplification refractory mutation system-quantitative real-time polymerase chain reaction,and C-MET amplification by fluorescence in situ hybridization.The clinicopathological features and survival data of the patients newly diagnosed with lung adenocarcinoma with both EGFR mutation and C-MET amplification were analyzed retrospectively.Results In 11 cases of EGFR mutation combined with C-MET amplification,complex glands and solid high-grade components were observed under a microscope in 10 cases except for one case with a cell block,the tissue structure of which was difficult to be evaluated.The incidence of lung adenocarcinoma in the patients with EGFR mutation combined with C-MET amplification at clinical stage Ⅳ was higher than that in the EGFR mutation or C-MET amplification group (all P<0.001),whereas the difference was not statistically significant between the EGFR mutation group and C-MET amplification group at each clinical stage (all P>0.05).There was no significant difference in the trend of survival rate between EGFR gene group and C-MET amplification group (χ2=0.042,P=0.838),while the survival of the patients with EGFR mutation combined with C-MET amplification was worse than that of the patients with EGFR mutation (χ2=246.72,P<0.001) or C-MET amplification (χ2=236.41,P<0.001).Conclusions The patients newly diagnosed with lung adenocarcinoma with EGFR mutation plus C-MET amplification demonstrate poor histological differentiation,rapid progress,and poor prognosis.The patients are often in the advanced stage when being diagnosed with cancer.Attention should be paid to this concurrent adverse driving molecular event in clinical work.With increasing availability,the inhibitors targeting C-MET may serve as an option to benefit these patients in the near future.


Assuntos
Adenocarcinoma de Pulmão , Neoplasias Pulmonares , Humanos , Hibridização in Situ Fluorescente , Estudos Retrospectivos , Prognóstico , Adenocarcinoma de Pulmão/genética , Mutação , Neoplasias Pulmonares/genética , Receptores ErbB/genética
7.
Talanta ; 265: 124803, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37331043

RESUMO

Three novel Co-based coordination polymers including {[Co(L)(µ3-O)1/3]2}n (1), {[Co(L)(bimb)]}n (2) and {[Co(L)(bimmb)1/2]}n (3) (H2L = 2,6-di(4-carboxylphenyl)-4-(4-(triazol-1-ylphenyl))pyridine), bimb = 1,4-bis(lmidazol) butane, bimmb = 1,4-bis(imidazole-1-ylmethyl)benzene) were successfully prepared under solvothermal conditions and characterized. Single-crystal X-ray diffraction analyses revealed that 1 possesses a 3D architecture composed of a trinuclear cluster [Co3N3(CO2)6(µ3-O)], 2 exhibits a 2D new topological framework with the point symbol (84·122)(8)2, whereas 3 shows a unique six-fold interpenetrated 3D framework with a (63·82·10)2(63)2(8) topology. Impressively, all of them can function as a highly selective and sensitive fluorescent sensor for the biomarker methylmalonic acid (MMA) via fluorescence quenching. The low detection limit, reusability and high anti-interference performance together make 1-3 become promising sensors for the practical detection of MMA. Furthermore, the successful application of MMA detection in urine sample was demonstrated, which may be a potential candidate for the further development of clinical diagnostic tools.


Assuntos
Benzeno , Ácido Metilmalônico , Biomarcadores , Corantes , Polímeros
8.
Front Physiol ; 14: 1287353, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38187138

RESUMO

Introduction: The moth species Athetis lepigone (Möschler) (Lepidoptera: Noctuidae), which has recently been identified as a pest of summer maize (Zea mays L.) in China, has demonstrated a rapid proliferation with in the Huang-Huai-Hai Plain region since its initial discovery in Hebei Province in 2005. It has become a prevalent pest of corn crops, and its ability to adapt quickly to its surroundings is currently being investigated. One of the key characteristics of its siphoning mouthparts is not only the feeding apparatus itself but also the chemosensory organs that enable the detection of chemical signals from the surrounding environment. However, there is a lack of comprehensive research on the genes responsible for chemosensory and metabolic mechanisms in the proboscises of male and female A. lepigone adults. Methods: In this study, we utilized transcriptome analysis to identify a total of fifty chemosensory genes from six distinct families, including 19 odorant-binding proteins (OBPs), 22 chemosensory proteins (CSPs), one co-receptor (Orco), six odorant receptors (ORs), four ionotropic receptors (IRs), and two sensory neuron membrane proteins (SNMPs) in the proboscis. Notably, seven OBPs, two CSPs, and one OR were discovered for the first time. Additionally, fourteen genes related to metabolism, including cytochrome P450 (CYPs) and carboxylesterases (CXEs), were also identified. Furthermore, a qualitative analysis was conducted on the relative transcript levels of eight related genes. The expression of 21 annotated chemosensory and metabolic genes was compared between A. lepigone adults and larvae using qRT-PCR, revealing tissue specificity. The majority of genes exhibited predominant expression in the antennae and proboscis during the adult stage, while showing slight expression in the combination of sixth-instar larval head oral appendages (maxilla, labium, and antenna) and pheromone gland-ovipositors of female adults. Results/discussion: Our study points to a new pest control strategies that these newly discovered genes have the potential to serve as targets for enhancing future pest control, including mating disruption and the use of food attractants. And it would be advantageous to ascertain the distribution of chemosensory gene expression and gain insights into the functionalities of these genes, thereby establishing a novel theoretical framework for the advancement of eco-friendly pesticides and efficient pest management strategies in the future.

9.
Natl Sci Rev ; 9(4): nwab225, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35530436

RESUMO

The microscopic understanding of high-temperature superconductivity in cuprates has been hindered by the apparent complexity of crystal structures in these materials. We used scanning tunneling microscopy and spectroscopy to study the electron-doped copper oxide compound Sr1- x Nd x CuO2, which has only bare cations separating the CuO2 planes and thus the simplest infinite-layer structure of all cuprate superconductors. Tunneling conductance spectra of the major CuO2 planes in the superconducting state revealed direct evidence for a nodeless pairing gap, regardless of variation of its magnitude with the local doping of trivalent neodymium. Furthermore, three distinct bosonic modes are observed as multiple peak-dip-hump features outside the superconducting gaps and their respective energies depend little on the spatially varying gaps. As well as the bosonic modes, with energies identical to those of the external, bending and stretching phonons of copper oxides, our findings reveal the origin of the bosonic modes in lattice vibrations rather than spin excitations.

10.
Phys Rev Lett ; 128(12): 126402, 2022 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-35394299

RESUMO

Here, we visualize the trapping of topological surface states in the circular n-p junctions on the top surface of the seven-quintuple-layer three dimensional (3D) topological insulator (TI) Sb_{2}Te_{3} epitaxial films. As shown by spatially dependent and field-dependent tunneling spectra, these trapped resonances show field-induced splittings between the degenerate time-reversal-symmetric states at zero magnetic field. These behaviors are attributed unambiguously to Berry-phase switch by comparing the experimental data with both numerical and semiclassical simulations. The successful electrostatic trapping of topological surface states in epitaxial films and the observation of Berry-phase switch provide a rich platform of exploiting new ideas for TI-based quantum devices.

11.
Proc Natl Acad Sci U S A ; 119(8)2022 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-35181607

RESUMO

Interface phonon modes that are generated by several atomic layers at the heterointerface play a major role in the interface thermal conductance for nanoscale high-power devices such as nitride-based high-electron-mobility transistors and light-emitting diodes. Here we measure the local phonon spectra across AlN/Si and AlN/Al interfaces using atomically resolved vibrational electron energy-loss spectroscopy in a scanning transmission electron microscope. At the AlN/Si interface, we observe various interface phonon modes, of which the extended and localized modes act as bridges to connect the bulk AlN modes and bulk Si modes and are expected to boost the phonon transport, thus substantially contributing to interface thermal conductance. In comparison, no such phonon bridge is observed at the AlN/Al interface, for which partially extended modes dominate the interface thermal conductivity. This work provides valuable insights into understanding the interfacial thermal transport in nitride semiconductors and useful guidance for thermal management via interface engineering.

12.
Food Sci Nutr ; 9(5): 2508-2516, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-34026067

RESUMO

The aim of this study was to identify the locations and harvest months in Guizhou province, China, producing the most suitable red dragon fruit (Hylocereus polyrhizus) for winemaking. Fruit from Guanling, Luodian and Zhenfeng counties was harvested separately from successive fruit cycles in August, September and October, respectively. The key traits measured were fruit weight, pulp yield, soluble solids content, and titratable acid. Wine characteristics measured were alcohol content, total carbohydrates, titratable acidity, volatile acidity, and betacyanin content. The overall suitability of fruit from each location for winemaking was evaluated using a multi-factor, unweighted, scorecard. On that basis, fruit from Guanling county harvested in August was the most suitable. Fruit from Luodian, and Zhenfeng was most suitable when harvested in August and September, and September, respectively. These results provide a preliminary guide for the sourcing of red dragon fruit from Guizhou for wine production.

13.
Anal Methods ; 12(42): 5097-5102, 2020 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-33047756

RESUMO

Carbon dots (CDs) with blue fluorescence were synthesized using indole-3-butyric acid and l-tryptophan using a one-step hydrothermal method. The CDs were further employed as a fluorescent sensor with high selectivity for colorimetric and ratiometric detection of tetracycline (TC) in water. The limit of detection (LOD) was found to be 0.33 µM for TC with R2 = 0.98387. Besides, the CDs could be applied in practical water samples and showed good recovery.


Assuntos
Corantes Fluorescentes , Pontos Quânticos , Carbono , Colorimetria , Limite de Detecção
14.
Phys Rev Lett ; 125(7): 077002, 2020 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-32857570

RESUMO

Identifying the essence of doped Mott insulators is one of the major outstanding problems in condensed matter physics and the key to understanding the high-temperature superconductivity in cuprates. We report real space visualization of Mott insulator-metal transition in Sr_{1-x}La_{x}CuO_{2+y} cuprate films that cover both the electron- and hole-doped regimes. Tunneling conductance measurements directly on the copper-oxide (CuO_{2}) planes reveal a systematic shift in the Fermi level, while the fundamental Mott-Hubbard band structure remains unchanged. This is further demonstrated by exploring the atomic-scale electronic response of CuO_{2} to substitutional dopants and intrinsic defects in a sister compound Sr_{0.92}Nd_{0.08}CuO_{2}. The results may be better explained in the framework of self-modulation doping, similar to that in semiconductor heterostructures, and form a basis for developing any microscopic theories for cuprate superconductivity.

15.
Phys Rev Lett ; 124(18): 187001, 2020 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-32441977

RESUMO

Alkali-fulleride superconductors with a maximum critical temperature T_{c}∼40 K exhibit a similar electronic phase diagram to that of unconventional high-T_{c} superconductors. Here we employ cryogenic scanning tunneling microscopy to show that trilayer K_{3}C_{60} displays fully gapped strong coupling s-wave superconductivity, accompanied by a pseudogap above T_{c}∼22 K and within vortices. A precise control of the electronic correlations and potassium doping enables us to reveal that superconductivity occurs near a superconductor-Mott-insulator transition and reaches maximum at half-filling. The s-wave symmetry retains over the entire phase diagram, which, in conjunction with an abrupt decline of the superconductivity below half-filling, indicates that alkali fullerides are predominantly phonon-mediated superconductors, although the electronic correlations also come into play.

16.
ACS Nano ; 14(1): 196-203, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31800218

RESUMO

The continuing increase of the efficiency of perovskite solar cells has pushed the internal quantum efficiency approaching 100%, which means the light-to-carrier and then the following carrier transportation and extraction are no longer limiting factors in photoelectric conversion efficiency of perovskite solar cells. However, the optimal efficiency is still far lower than the Shockley-Queisser efficiency limit, especially for those inverted perovskite solar cells, indicating that a significant fraction of light does not transmit into the active perovskite layer to be absorbed there. Here, a planar inverted perovskite solar cell (ITO/PTAA/perovskite/PC61BM/bathocuproine (BCP)/Ag) is chosen as an example, and we show that its external quantum efficiency (EQE) can be significantly improved by simply texturing the poly[bis (4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) layer. By washing the film prepared from a mixed polymer solution of PTAA and polystyrene (PS), a textured PTAA/perovskite interface is introduced on the light-input side of perovskite to inhibit internal optical reflection. The reduction of optical loss by this simple texture method increases the EQE and then the photocurrent of the ITO/PTAA/perovskite/PC61BM/BCP/Ag device with the magnitude of about 10%. At the same time, this textured PTAA benefits the band edge absorption in this planar solar cell. The large increase of the short-circuit current together with the increase of fill factor pushes the efficiency of this inverted perovskite solar cell from 18.3% up to an efficiency over 20.8%. By using an antireflection coating on glass to let more light into the device, the efficiency is further improved to 21.6%, further demonstrating the importance of light management in perovskite solar cells.

17.
ChemSusChem ; 12(16): 3808-3816, 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31216377

RESUMO

Organic-inorganic halide perovskite solar cells (PSCs) have reached certified efficiencies of over 23 % with expensive organic hole-transporting materials. However, the use of an inorganic hole-transport layer (HTL) remains crucial as it would reduce cost combined with higher mobility and stability. In this direction, the application of Cu2 O as the top layer in PSCs is still complicated owing to the difficulty of solution processing. Herein, a solution-processing method is reported for preparing Cu2 O nanocubes as a p-type HTL in regular structure (n-i-p) PSCs. The controlled synthesis of Cu2 O nanocubes in a size range of 60-80 nm is achieved without using any surfactants, which are usually toxic and tricky to remove. The new structure of these Cu2 O nanocubes enhances the carrier mobility with preferable energy alignment to the perovskite layer and superb stability. The PSCs based on these Cu2 O nanocubes HTMs could achieve an efficiency exceeding 17 % with high stability, whereas organic P3HT-based PSCs display an efficiency of 15.59 % with a poorer running stability. This indicates that Cu2 O nanocubes are a promising HTM for efficient and stable PSCs.

18.
ACS Appl Mater Interfaces ; 11(24): 22021-22027, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31140268

RESUMO

Poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) plays an important role in inverted planar perovskite solar cells (IPPSCs) as an efficient hole extraction and transfer layer (HTL). The IPPSCs based on PEDOT:PSS normally display inferior performance with a reduced open-circuit voltage. To address this problem, here sodium citrate-doped PEDOT:PSS is adopted as an effective HTL for improving the performance of IPPSCs. Sodium citrate-doped PEDOT:PSS HTL improves the conversion efficiency of IPPSCs from 15.05% of reference cells to 18.39%. The large increase of the open-circuit voltage ( VOC) from 1.057 to 1.134 V is the main source for this performance enhancement. With the help of characterization analysis of ultraviolet photoelectron spectroscopy, scanning electron microscopy, electrochemical impedance spectroscopy, etc., the higher work function of the doped PEDOT:PSS film and the uniform crystallinity of the perovskite film on it are disclosed as the reasons for the increased VOC and the consequent performance enhancement.

19.
Sci Adv ; 5(5): eaaw3988, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31114808

RESUMO

The surface of a three-dimensional topological insulator (TI) hosts two-dimensional massless Dirac fermions (DFs), the gapless and spin-helical nature of which leads to their high transmission through surface defects or potential barriers. Here, we report the behaviors of topological surface states (TSS) in a triangular quantum corral (TQC) which, unlike a circular corral, is supposed to be totally transparent for DFs. By real-space mapping of the electronic structure of TQCs, both the trapping and detrapping behaviors of the TSS are observed. The selection rules are found to be governed by the geometry and spin texture of the constant energy contour of TSS upon the strong hexagonal warping in Bi2Te3. Our work indicates the extended nature of TSS and elucidates the selection rules of the trapping of TSS in the presence of a complicated surface state structure, giving insights into the effective engineering of DFs in TIs.

20.
Adv Mater ; 30(1)2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29125706

RESUMO

The quantum anomalous Hall (QAH) effect, which has been realized in magnetic topological insulators (TIs), is the key to applications of dissipationless quantum Hall edge states in electronic devices. However, investigations and utilizations of the QAH effect are limited by the ultralow temperatures needed to reach full quantization-usually below 100 mK in either Cr- or V-doped (Bi,Sb)2 Te3 of the two experimentally confirmed QAH materials. Here it is shown that by codoping Cr and V magnetic elements in (Bi,Sb)2 Te3 TI, the temperature of the QAH effect can be significantly increased such that full quantization is achieved at 300 mK, and zero-field Hall resistance of 0.97 h/e2 is observed at 1.5 K. A systematic transport study of the codoped (Bi,Sb)2 Te3 films with varied Cr/V ratios reveals that magnetic codoping improves the homogeneity of ferromagnetism and modulates the surface band structure. This work demonstrates magnetic codoping to be an effective strategy for achieving high-temperature QAH effect in TIs.

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