An intrinsic magnetic topological insulator(TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel ...An intrinsic magnetic topological insulator(TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi2Te4, by alternate growth of a Bi2Te3 quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.展开更多
We train a neural network to identify impurities in the experimental images obtained by the scanning tunneling microscope(STM)measurements.The neural network is first trained with a large number of simulated data and ...We train a neural network to identify impurities in the experimental images obtained by the scanning tunneling microscope(STM)measurements.The neural network is first trained with a large number of simulated data and then the trained neural network is applied to identify a set of experimental images taken at different voltages.We use the convolutional neural network to extract features from the images and also implement the attention mechanism to capture the correlations between images taken at different voltages.We note that the simulated data can capture the universal Friedel oscillation but cannot properly describe the non-universal physics short-range physics nearby an impurity,as well as noises in the experimental data.And we emphasize that the key of this approach is to properly deal with these differences between simulated data and experimental data.Here we show that even by including uncorrelated white noises in the simulated data,the performance of the neural network on experimental data can be significantly improved.To prevent the neural network from learning unphysical short-range physics,we also develop another method to evaluate the confidence of the neural network prediction on experimental data and to add this confidence measure into the loss function.We show that adding such an extra loss function can also improve the performance on experimental data.Our research can inspire future similar applications of machine learning on experimental data analysis.展开更多
We have developed a low-damage photolithography method for magnetically doped(Bi,Sb)_(2)Te_(3)quantum anomalous Hall(QAH) thin films incorporating an additional resist layer of poly(methyl methacrylate)(PMMA). By perf...We have developed a low-damage photolithography method for magnetically doped(Bi,Sb)_(2)Te_(3)quantum anomalous Hall(QAH) thin films incorporating an additional resist layer of poly(methyl methacrylate)(PMMA). By performing control experiments on the transport properties of five devices at varied gate voltages(V_(g)s), we revealed that the modified photolithography method enables fabricating QAH devices with the transport and magnetic properties unaffected by fabrication process. Our experiment represents a step towards the production of novel micro-structured electronic devices based on the dissipationless QAH chiral edge states.展开更多
We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca_(3)Cu_(2)O_(4)Cl_(2) parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the F...We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca_(3)Cu_(2)O_(4)Cl_(2) parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the Fermi energy with increasing temperature, while the charge transfer band remains basically unchanged. This leads to a reduction of the charge transfer gap size at high temperatures, and the rate of reduction is much faster than that of conventional semiconductors. Across the Neel temperature for antiferromagnetic order, there is no sudden change in the electronic structure. These results shed new light on the theoretical models about the parent Mott insulator of cuprates.展开更多
Duchenne muscular dystrophy(DMD)is a fatal X-chromosome-linked genetic disease caused by dystrophin gene mutations,including nonsense mutations.1 Nonsense mutations are caused by the introduction of premature terminat...Duchenne muscular dystrophy(DMD)is a fatal X-chromosome-linked genetic disease caused by dystrophin gene mutations,including nonsense mutations.1 Nonsense mutations are caused by the introduction of premature termination codons,which prevent translation of full-length proteins.Read-through therapies show potential for addressing DMD's genetic basis;however,issues such as non-specific amino acid insertions,gene-editing delivery challenges,and clinical safety concerns have limited their progress.2,3 To address nonsense mutations,nonsense suppressor transfer RNAs(sup-tRNAs)have been proposed as a genetic therapy approach.3,4,5 In this study,we propose a new MyoAAV-delivered suppressor tRNA(sup-tRNA)strategy to restore dystrophin expression.Our approach specifically targets nonsense mutations in mdx mice and patient-derived myoblasts and cardiomyocytes,significantly increasing dystrophin levels,especially in the heart(up to 61.43%when combined with CC-90009).This combination alleviates dystrophic symptoms and improves read-through efficiency,likely by reducing translation termination factor activity.These findings highlight the potential of sup-tRNA in DMD and other nonsense mutation-related diseases.展开更多
The simultaneous modulation of electric and optical properties in graphene is essential for advancing high-performance applications in optoelectronics.However,achieving in-situ control of multiple electric and optical...The simultaneous modulation of electric and optical properties in graphene is essential for advancing high-performance applications in optoelectronics.However,achieving in-situ control of multiple electric and optical states in graphene devices remains a challenge.Here we demonstrate a versatile and reversible electric-field control of organic-ion intercalation from bilayer to pentalayer graphene.Through simultaneous optical imaging and electric measurements,we reveal multiple physical states controlled by the layer-by-layer intercalation processes,resulting in both high transparency and high electric conductance with an increase in the number of intercalated layers.Raman spectroscopy demonstrates that the intercalated graphene maintains a high carrier concentration without lattice degradation.Moreover,Hall effect measurements reveal that the carrier density can reach approximately 1.5×10^(14)cm^(-2)per layer.The ability to synchronously control the transparency and conductance states by adjusting the number of ion-intercalated layers highlights the potential of multistate modulation for the development of advanced optoelectronic devices in two-dimensional materials.展开更多
The topological quantum phases in antiferromagnetic topological insulator MnBi_(2)Te_(4)hold promise for next-generation spintronics,but their experimental realization has been constrained by challenges in preparing h...The topological quantum phases in antiferromagnetic topological insulator MnBi_(2)Te_(4)hold promise for next-generation spintronics,but their experimental realization has been constrained by challenges in preparing high-quality devices.In this work,we report a new wax-assisted exfoliation and transfer method that enables the fabrication of MnBi_(2)Te_(4)heterostructures with both surfaces encapsulated by AlO_(x).This strategy strongly enhances the transport performances of the topological quantum phases in MnBi_(2)Te_(4)flakes,which is attributed to the enhancement of magnetism by the AlO_(x)layer.We observe the robust axion insulator state in even-layer device with wide zero Hall plateau and high longitudinal resistivity,and the quantum anomalous Hall effect in odd-layer device with large hysteresis and sharp plateau transition.These results demonstrate that the combination of wax exfoliation and AlO_(x)encapsulation provides great potentials for exploring novel topological quantum phenomena and potential applications in MnBi2Te4 and other two-dimensional materials.展开更多
Plants establish symbioses with mutualistic fungi,such as arbuscular mycorrhizal(AM)fungi,and bacteria,such as rhizobia,to exchange key nutrients and thrive.Plants and symbionts have coevolved and represent vital comp...Plants establish symbioses with mutualistic fungi,such as arbuscular mycorrhizal(AM)fungi,and bacteria,such as rhizobia,to exchange key nutrients and thrive.Plants and symbionts have coevolved and represent vital components of terrestrial ecosystems.Plants employ an ancestral AM signaling pathway to establish intracellular symbioses,including the legume–rhizobia symbiosis,in their roots.Nevertheless,the relationship between the AM and rhizobial symbioses in native soil is poorly understood.Here,we examined how these distinct symbioses affect root-associated bacterial communities in Medicago truncatula by performing quantitative microbiota profiling(QMP)of 16S rRNA genes.We found that M.truncatula mutants that cannot establish AM or rhizobia symbiosis have an altered microbial load(quantitative abundance)in the rhizosphere and roots,and in particular that AM symbiosis is required to assemble a normal quantitative root-associated microbiota in native soil.Moreover,quantitative microbial co-abundance network analyses revealed that AM symbiosis affects Rhizobiales hubs among plant microbiota and benefits the plant holobiont.Through QMP of rhizobial rpoB and AM fungal SSU rRNA genes,we revealed a new layer of interaction whereby AM symbiosis promotes rhizobia accumulation in the rhizosphere of M.truncatula.We further showed that AM symbiosis-conditioned microbial communities within the M.truncatula rhizosphere could promote nodulation in different legume plants in native soil.Given that the AM and rhizobial symbioses are critical for crop growth,our findings might inform strategies to improve agricultural management.Moreover,our work sheds light on the co-evolution of these intracellular symbioses during plant adaptation to native soil conditions.展开更多
We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screenin...We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.展开更多
One of the biggest puzzles concerning the cup- rate high temperature superconductors is what determines the maximum transition temperature （Tc,max）, which varies from less than 30 to above 130 K in different compoun...One of the biggest puzzles concerning the cup- rate high temperature superconductors is what determines the maximum transition temperature （Tc,max）, which varies from less than 30 to above 130 K in different compounds. Despite this dramatic variation, a robust trend is that within each family, the double-layer compound always has higher Tc,max than the single-layer counterpart. Here we use scanning tunneling microscopy to investigate the electronic structure of four cuprate parent compounds belonging to two different families. We find that within each family, the double layer compound has a much smaller charge transfer gap size （ACT）, indicating a clear anticorrelation between AcT and Tc,max. These results suggest that the charge transfer gap plays a key role in the superconducting physics of cuprates, which shed important new light on the high To mechanism from doped Mott insulator perspective.展开更多
Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling mic...Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of Cr_2Ge_2Te_6.Tunneling spectroscopy reveals a surprising large energy level shift and change of energy gap size across the ferromagnetic to paramagnetic phase transition,as well as a peculiar double-peak electronic state on the Cr-site defect.These features can be quantitatively explained by density functional theory calculations,which uncover a close relationship between the electronic structure and magnetic order.These findings shed important new lights on the microscopic electronic structure and origin of magnetic order in Cr_2Ge_2Te_6.展开更多
We use scanning tunneling microscopy to visualize the atomic-scale electronic states induced by a pair of hole dopants in Ca_(2)CuO_(2)Cl_(2)parent Mott insulator of cuprates.We find that when the two dopants approach...We use scanning tunneling microscopy to visualize the atomic-scale electronic states induced by a pair of hole dopants in Ca_(2)CuO_(2)Cl_(2)parent Mott insulator of cuprates.We find that when the two dopants approach each other,the transfer of spectral weight from high energy Hubbard band to low energy ingap state creates a broad peak and nearly V-shaped gap around the Fermi level.The peak position shows a sudden drop at distance around 4 a_(0)and then remains almost constant.The in-gap states exhibit peculiar spatial distributions depending on the configuration of the two dopants relative to the underlying Cu lattice.These results shed important new lights on the evolution of low energy electronic states when a few holes are doped into parent cuprates.展开更多
The chirality associated with broken time-reversal symmetry in magnetically doped topological insulators has important implications for the quantum transport phenomena.Here we report anomalous Hall effect studies in M...The chirality associated with broken time-reversal symmetry in magnetically doped topological insulators has important implications for the quantum transport phenomena.Here we report anomalous Hall effect studies in Mn-and Cr-doped Bi_(2)Te_(3) topological insulators with varied thicknesses and doping contents.By tracing the magnitude of the anomalous Hall resistivity,we find that the Mn-type anomalous Hall effect characterized with clockwise chirality is strengthened by the reduction of film thickness,which is opposite to that of the Cr-type anomalous Hall effect with counterclockwise chirality.We provide a phenomenological physical picture to explain the evolution of the magnetic order and the anomalous Hall chirality in magnetically doped topological insulators.展开更多
The feminization-1c(fem-1c)gene has been shown to be associated with sex differentiation and determination in many metazoan species.It belongs to the fem-1 family which is a member of the ANK superfamily.In this study...The feminization-1c(fem-1c)gene has been shown to be associated with sex differentiation and determination in many metazoan species.It belongs to the fem-1 family which is a member of the ANK superfamily.In this study,the full-length cDNA of the fem-1c(Hcfem-1c)gene was isolated from the freshwater mussel(Hypriopsis cumingii).The isolated Hcfem-1c cDNA was 2196 bp in length and encoded a putative protein of 621 amino acids that contains seven ANK domains.Phylogenetic analysis of the deduced HcFEM-1C protein showed that it clustered with the other invertebrates homologues,indicating that the sequence of HcFEM-1C was conserved during evolution.Quantitative real-time PCR(qPCR)expression revealed that the Hcfem-1c gene was expressed in the adductor muscle,foot,liver,gill,kidney,mantle,and gonads of male and female adult mussels(two years old).In the gonads Hcfem-1c was much less abundant in males than that in females.During early development of the gonads,Hcfem-1c transcripts were significantly increased in the primordial germ cell differentiation stage(5 months old).We hypothesized that Hcfem-1c probably regulates female gonad differentiation.In situ hybridization showed that a strong and specific signal concentrated in the female oocyte cell membrane and male follicular wall,indicating that Hcfem-1c gene may not only be involved in female gonad differentiation,but also participates in egg development.This study laid the foundations for a better understanding of gender differentiation mechanism in H.cumingii.展开更多
Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations,due to their distinct vortex structures and upper critical field values.Here,we utilize the pla...Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations,due to their distinct vortex structures and upper critical field values.Here,we utilize the planar tunnel junction technique to perform continuous magnetic field-dependent dI/dV spectroscopy measurements on 2H-NbSe_(2) under different field orientations.We observe characteristic kink features for weak in-plane magnetic fields,but the overall behaviors are quite similar for different field orientations despite the distinct vortex generation processes and widely different upper critical field values.Especially,the generic square root dependence of the Fermi level density of state on magnetic field indicates that the Doppler shift plays a central role in the low energy excitations of 2H-NbSe_(2) in the presence of magnetic field.展开更多
基金Supported by the Ministry of Science and Technology of Chinathe National Science Foundation of Chinathe Beijing Advanced Innovation Center for Future Chip(ICFC)
文摘An intrinsic magnetic topological insulator(TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi2Te4, by alternate growth of a Bi2Te3 quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.
基金supported by Beijing Outstanding Scholar Programthe National Key Research and Development Program of China(Grant No. 2016YFA0301600)+3 种基金the National Natural Science Foundation of China(Grant No. 11734010)supported by a startup fund from UCSDsupported by the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China
文摘We train a neural network to identify impurities in the experimental images obtained by the scanning tunneling microscope(STM)measurements.The neural network is first trained with a large number of simulated data and then the trained neural network is applied to identify a set of experimental images taken at different voltages.We use the convolutional neural network to extract features from the images and also implement the attention mechanism to capture the correlations between images taken at different voltages.We note that the simulated data can capture the universal Friedel oscillation but cannot properly describe the non-universal physics short-range physics nearby an impurity,as well as noises in the experimental data.And we emphasize that the key of this approach is to properly deal with these differences between simulated data and experimental data.Here we show that even by including uncorrelated white noises in the simulated data,the performance of the neural network on experimental data can be significantly improved.To prevent the neural network from learning unphysical short-range physics,we also develop another method to evaluate the confidence of the neural network prediction on experimental data and to add this confidence measure into the loss function.We show that adding such an extra loss function can also improve the performance on experimental data.Our research can inspire future similar applications of machine learning on experimental data analysis.
基金supported by the National Key Research and Development Program of China (Grant No. 2018YFA0307100)the Basic Science Center Project of the National Natural Science Foundation of China (Grant No. 52388201)+4 种基金the National Natural Science Foundation of China (Grant Nos. 12274453 and 92065206)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302502)supported by Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics (Grant No. KF202204)supported by the New Cornerstone Science Foundation through the New Cornerstone Investigator Programthe XPLORER PRIZE。
文摘We have developed a low-damage photolithography method for magnetically doped(Bi,Sb)_(2)Te_(3)quantum anomalous Hall(QAH) thin films incorporating an additional resist layer of poly(methyl methacrylate)(PMMA). By performing control experiments on the transport properties of five devices at varied gate voltages(V_(g)s), we revealed that the modified photolithography method enables fabricating QAH devices with the transport and magnetic properties unaffected by fabrication process. Our experiment represents a step towards the production of novel micro-structured electronic devices based on the dissipationless QAH chiral edge states.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFA0302900)the Basic Science Center Project of the National Natural Science Foundation of China (Grant No. 51788104)supported in part by the Beijing Advanced Innovation Center for Future Chip (ICFC)。
文摘We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca_(3)Cu_(2)O_(4)Cl_(2) parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the Fermi energy with increasing temperature, while the charge transfer band remains basically unchanged. This leads to a reduction of the charge transfer gap size at high temperatures, and the rate of reduction is much faster than that of conventional semiconductors. Across the Neel temperature for antiferromagnetic order, there is no sudden change in the electronic structure. These results shed new light on the theoretical models about the parent Mott insulator of cuprates.
基金supported by the National Key Research and Development Program of China(No.2022YFC2703600)the National Natural Science Foundation of China(No.81930121).
文摘Duchenne muscular dystrophy(DMD)is a fatal X-chromosome-linked genetic disease caused by dystrophin gene mutations,including nonsense mutations.1 Nonsense mutations are caused by the introduction of premature termination codons,which prevent translation of full-length proteins.Read-through therapies show potential for addressing DMD's genetic basis;however,issues such as non-specific amino acid insertions,gene-editing delivery challenges,and clinical safety concerns have limited their progress.2,3 To address nonsense mutations,nonsense suppressor transfer RNAs(sup-tRNAs)have been proposed as a genetic therapy approach.3,4,5 In this study,we propose a new MyoAAV-delivered suppressor tRNA(sup-tRNA)strategy to restore dystrophin expression.Our approach specifically targets nonsense mutations in mdx mice and patient-derived myoblasts and cardiomyocytes,significantly increasing dystrophin levels,especially in the heart(up to 61.43%when combined with CC-90009).This combination alleviates dystrophic symptoms and improves read-through efficiency,likely by reducing translation termination factor activity.These findings highlight the potential of sup-tRNA in DMD and other nonsense mutation-related diseases.
基金supported by the National Natural Science Foundation of China(Grant Nos.12274252,and 12350404)the Basic Science Center Project of NSFC(Grant No.52388201)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302502)。
文摘The simultaneous modulation of electric and optical properties in graphene is essential for advancing high-performance applications in optoelectronics.However,achieving in-situ control of multiple electric and optical states in graphene devices remains a challenge.Here we demonstrate a versatile and reversible electric-field control of organic-ion intercalation from bilayer to pentalayer graphene.Through simultaneous optical imaging and electric measurements,we reveal multiple physical states controlled by the layer-by-layer intercalation processes,resulting in both high transparency and high electric conductance with an increase in the number of intercalated layers.Raman spectroscopy demonstrates that the intercalated graphene maintains a high carrier concentration without lattice degradation.Moreover,Hall effect measurements reveal that the carrier density can reach approximately 1.5×10^(14)cm^(-2)per layer.The ability to synchronously control the transparency and conductance states by adjusting the number of ion-intercalated layers highlights the potential of multistate modulation for the development of advanced optoelectronic devices in two-dimensional materials.
基金supported by the Basic Science Center Project of the National Natural Science Foundation of China(52388201 and 12274453)the Innovation program for Quantum Science and Technology(2021ZD0302502 and 2021ZD0302502)+1 种基金the Beijing Nova Program(20240484574)the New Cornerstone Science Foundation through the New Cornerstone Investigator Program.
文摘The topological quantum phases in antiferromagnetic topological insulator MnBi_(2)Te_(4)hold promise for next-generation spintronics,but their experimental realization has been constrained by challenges in preparing high-quality devices.In this work,we report a new wax-assisted exfoliation and transfer method that enables the fabrication of MnBi_(2)Te_(4)heterostructures with both surfaces encapsulated by AlO_(x).This strategy strongly enhances the transport performances of the topological quantum phases in MnBi_(2)Te_(4)flakes,which is attributed to the enhancement of magnetism by the AlO_(x)layer.We observe the robust axion insulator state in even-layer device with wide zero Hall plateau and high longitudinal resistivity,and the quantum anomalous Hall effect in odd-layer device with large hysteresis and sharp plateau transition.These results demonstrate that the combination of wax exfoliation and AlO_(x)encapsulation provides great potentials for exploring novel topological quantum phenomena and potential applications in MnBi2Te4 and other two-dimensional materials.
基金The research was supported by the Chinese Academy of Sciences(ZDRW-ZS-2019-2)the National Natural Science Foundation of China(31825003,31730103,and 31970323)+1 种基金the Strategic Priority Research Program"Molecular Mechanism of Plant Growth and Development"of the Chinese Academy of Sciences(XDB27040207)the China National GeneBank(CNGB).
文摘Plants establish symbioses with mutualistic fungi,such as arbuscular mycorrhizal(AM)fungi,and bacteria,such as rhizobia,to exchange key nutrients and thrive.Plants and symbionts have coevolved and represent vital components of terrestrial ecosystems.Plants employ an ancestral AM signaling pathway to establish intracellular symbioses,including the legume–rhizobia symbiosis,in their roots.Nevertheless,the relationship between the AM and rhizobial symbioses in native soil is poorly understood.Here,we examined how these distinct symbioses affect root-associated bacterial communities in Medicago truncatula by performing quantitative microbiota profiling(QMP)of 16S rRNA genes.We found that M.truncatula mutants that cannot establish AM or rhizobia symbiosis have an altered microbial load(quantitative abundance)in the rhizosphere and roots,and in particular that AM symbiosis is required to assemble a normal quantitative root-associated microbiota in native soil.Moreover,quantitative microbial co-abundance network analyses revealed that AM symbiosis affects Rhizobiales hubs among plant microbiota and benefits the plant holobiont.Through QMP of rhizobial rpoB and AM fungal SSU rRNA genes,we revealed a new layer of interaction whereby AM symbiosis promotes rhizobia accumulation in the rhizosphere of M.truncatula.We further showed that AM symbiosis-conditioned microbial communities within the M.truncatula rhizosphere could promote nodulation in different legume plants in native soil.Given that the AM and rhizobial symbioses are critical for crop growth,our findings might inform strategies to improve agricultural management.Moreover,our work sheds light on the co-evolution of these intracellular symbioses during plant adaptation to native soil conditions.
基金supported by the National Natural Science Foundation and Ministry of Science and Technology of China(2015CB921000 and 2012CB921402)Yihua Wang is partially supported by the Urbanek Fellowship of the Department of Applied Physics at Stanford UniversityK.A.Moler is supported by the Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division,under Contract DEAC02-76SF00515
文摘We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.
基金supported by the National Natural Science Foundation of China and Ministry of Science and Technology of the People’s Republic of Chinafinancial support from the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB07020300)
文摘One of the biggest puzzles concerning the cup- rate high temperature superconductors is what determines the maximum transition temperature （Tc,max）, which varies from less than 30 to above 130 K in different compounds. Despite this dramatic variation, a robust trend is that within each family, the double-layer compound always has higher Tc,max than the single-layer counterpart. Here we use scanning tunneling microscopy to investigate the electronic structure of four cuprate parent compounds belonging to two different families. We find that within each family, the double layer compound has a much smaller charge transfer gap size （ACT）, indicating a clear anticorrelation between AcT and Tc,max. These results suggest that the charge transfer gap plays a key role in the superconducting physics of cuprates, which shed important new light on the high To mechanism from doped Mott insulator perspective.
基金supported by the Basic Science Center Project of NSFC(51788104)the MOST of China(2015CB921000)+6 种基金the support from Tsinghua University Initiative Scientific Research Program and NSFC(11774196)S.H.Z.is supported by the National Postdoctoral Program for Innovative Talents of China(BX201600091)the China Postdoctoral Science Foundation(2017M610858)the support of the National Key Research and Development Program(2016YFA0300404)NSFC Grant(11674326)the Joint Funds of NSFC and the Chinese Academy of Sciences’Large-Scale Scientific Facility(U1432139)supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC)
文摘Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of Cr_2Ge_2Te_6.Tunneling spectroscopy reveals a surprising large energy level shift and change of energy gap size across the ferromagnetic to paramagnetic phase transition,as well as a peculiar double-peak electronic state on the Cr-site defect.These features can be quantitatively explained by density functional theory calculations,which uncover a close relationship between the electronic structure and magnetic order.These findings shed important new lights on the microscopic electronic structure and origin of magnetic order in Cr_2Ge_2Te_6.
基金the National Program on Key Basic Research Project of China(973 Program)(2017YFA0302900)the Basic Science Center Project of the National Natural Science Foundation of China(51788104)supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC)。
文摘We use scanning tunneling microscopy to visualize the atomic-scale electronic states induced by a pair of hole dopants in Ca_(2)CuO_(2)Cl_(2)parent Mott insulator of cuprates.We find that when the two dopants approach each other,the transfer of spectral weight from high energy Hubbard band to low energy ingap state creates a broad peak and nearly V-shaped gap around the Fermi level.The peak position shows a sudden drop at distance around 4 a_(0)and then remains almost constant.The in-gap states exhibit peculiar spatial distributions depending on the configuration of the two dopants relative to the underlying Cu lattice.These results shed important new lights on the evolution of low energy electronic states when a few holes are doped into parent cuprates.
基金This work was supported by the Basic Science Center Project of National Natural Science Foundation of China(Grant No.51788104)the National Key R&D Program of China(Grant Nos.2018YFA0307100,and 2018YFA0305603)This work was supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC).
文摘The chirality associated with broken time-reversal symmetry in magnetically doped topological insulators has important implications for the quantum transport phenomena.Here we report anomalous Hall effect studies in Mn-and Cr-doped Bi_(2)Te_(3) topological insulators with varied thicknesses and doping contents.By tracing the magnitude of the anomalous Hall resistivity,we find that the Mn-type anomalous Hall effect characterized with clockwise chirality is strengthened by the reduction of film thickness,which is opposite to that of the Cr-type anomalous Hall effect with counterclockwise chirality.We provide a phenomenological physical picture to explain the evolution of the magnetic order and the anomalous Hall chirality in magnetically doped topological insulators.
基金This work was supported by the National Natural Science Foundation of China[grant number 31772835]the Innovation Program of Shanghai Municipal Education Commission[grant number 13ZZ128]the Shanghai Collaborative Innovation Center for Aquatic Animal Genetics and Breeding[grant number ZF1206].
文摘The feminization-1c(fem-1c)gene has been shown to be associated with sex differentiation and determination in many metazoan species.It belongs to the fem-1 family which is a member of the ANK superfamily.In this study,the full-length cDNA of the fem-1c(Hcfem-1c)gene was isolated from the freshwater mussel(Hypriopsis cumingii).The isolated Hcfem-1c cDNA was 2196 bp in length and encoded a putative protein of 621 amino acids that contains seven ANK domains.Phylogenetic analysis of the deduced HcFEM-1C protein showed that it clustered with the other invertebrates homologues,indicating that the sequence of HcFEM-1C was conserved during evolution.Quantitative real-time PCR(qPCR)expression revealed that the Hcfem-1c gene was expressed in the adductor muscle,foot,liver,gill,kidney,mantle,and gonads of male and female adult mussels(two years old).In the gonads Hcfem-1c was much less abundant in males than that in females.During early development of the gonads,Hcfem-1c transcripts were significantly increased in the primordial germ cell differentiation stage(5 months old).We hypothesized that Hcfem-1c probably regulates female gonad differentiation.In situ hybridization showed that a strong and specific signal concentrated in the female oocyte cell membrane and male follicular wall,indicating that Hcfem-1c gene may not only be involved in female gonad differentiation,but also participates in egg development.This study laid the foundations for a better understanding of gender differentiation mechanism in H.cumingii.
基金supported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302502)funding provided by Shanghai Jiao Tong University.
文摘Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations,due to their distinct vortex structures and upper critical field values.Here,we utilize the planar tunnel junction technique to perform continuous magnetic field-dependent dI/dV spectroscopy measurements on 2H-NbSe_(2) under different field orientations.We observe characteristic kink features for weak in-plane magnetic fields,but the overall behaviors are quite similar for different field orientations despite the distinct vortex generation processes and widely different upper critical field values.Especially,the generic square root dependence of the Fermi level density of state on magnetic field indicates that the Doppler shift plays a central role in the low energy excitations of 2H-NbSe_(2) in the presence of magnetic field.
