The infinite-layer nickelates,proposed as analogs to superconducting cuprates,provide a promising platform for exploring the mechanisms of unconventional superconductivity.However,the superconductivity has been exclus...The infinite-layer nickelates,proposed as analogs to superconducting cuprates,provide a promising platform for exploring the mechanisms of unconventional superconductivity.However,the superconductivity has been exclusively observed in thin films under atmospheric pressure,underscoring the critical role of the heterointerface.展开更多
Phonons are the primary heat carriers in non-metallic solids.In compositionally heterogeneous materials,the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder ...Phonons are the primary heat carriers in non-metallic solids.In compositionally heterogeneous materials,the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder and strain fluctuations,while the effects of compositional fluctuation induced local phonon states are usually ignored.Here,by scanning transmission electron microscopy electron energy loss spectroscopy and sophisticated calculations,we identify the vibrational properties of ingredient-dependent interface phonon modes in Alx Ga1-x N and quantify their various contributions to the local interface thermal conductance.We demonstrate that atomic-scale compositional fluctuation has significant influence on the vibrational thermodynamic properties,highly affecting the mode ratio and vibrational amplitude of interface phonon modes and subsequently redistributing their modal contribution to the interface thermal conductance.Our work provides fundamental insights into understanding of local phonon-boundary interactions in nanoscale inhomogeneities,which reveal new opportunities for optimization of thermal properties via engineering ingredient distribution.展开更多
The law of language learning has a theoretical basis.Language learning is a process of active learning,not of passive acceptance.Situational teaching is the extension and development of constructivist teaching.The cor...The law of language learning has a theoretical basis.Language learning is a process of active learning,not of passive acceptance.Situational teaching is the extension and development of constructivist teaching.The correct use of situational teaching can stimulate students 125 interest,facilitate a harmonious relationship between teachers and students,as well as promote the cultivation of other skills among students,so as to improve the teaching quality of oral Chinese teaching as a foreign language and effectively complete the teaching task.However,there are some issues that should be emphasized when using the situational teaching method,such as how to create situations effectively,the problems that teachers should pay attention to when creating situations,and the principles of creating situations.展开更多
Surface phonon polaritons(SPh Ps) are potentially very attractive for subwavelength control and manipulation of light at the infrared to terahertz wavelengths. Probing their propagation behavior in nanostructures is c...Surface phonon polaritons(SPh Ps) are potentially very attractive for subwavelength control and manipulation of light at the infrared to terahertz wavelengths. Probing their propagation behavior in nanostructures is crucial to guide rational device design. Here, aided by monochromatic scanning transmission electron microscopy-electron energy loss spectroscopy technique, we measure the dispersion relation of SPh Ps in individual Si C nanorods and reveal the effects of size and shape. We find that the SPh Ps can be modulated by the geometric shape and size of Si C nanorods. The energy of SPh Ps shows redshift with decreasing radius and the surface optical phonon is mainly concentrated on the surface with large radius. Therefore, the fields can be precisely confined in specific positions by varying the size of the nanorod, allowing effective tuning at nanometer scale. The findings of this work are in agreement with dielectric response theory and numerical simulation, and provide novel strategies for manipulating light in polar dielectrics through shape and size control, enabling the design of novel nanoscale phononphotonic devices.展开更多
Confined low dimensional charges with high density such as two-dimensional electron gas(2 DEG)at interfaces and charged domain walls in ferroelectrics show great potential to serve as functional elements in future nan...Confined low dimensional charges with high density such as two-dimensional electron gas(2 DEG)at interfaces and charged domain walls in ferroelectrics show great potential to serve as functional elements in future nanoelectronics.However,stabilization and control of low dimensional charges is challenging,as they are usually subject to enormous depolarization fields.Here,we demonstrate a method to fabricate tunable charged interfaces with~77°,86°and 94°head-to-head polarization configurations in multiferroic Bi Fe O_(3) thin films by grain boundary engineering.The adjacent grains are cohesively bonded and the boundary is about 1 nm in width and devoid of any amorphous region.Remarkably,the polarization remains almost unchanged near the grain boundaries,indicating the polarization charges are well compensated,i.e.,there should be two-dimensional charge gas confined at grain boundaries.Adjusting the tilt angle of the grain boundaries enables tuning the angle of polarization configurations from 71°to 109°,which in turn allows the control of charge density at the grain boundaries.This general and feasible method opens new doors for the application of charged interfaces in next generation nanoelectronics.展开更多
基金supported by the National Natural Science Foundation of China[52125307(to P.G.),12404192(to R.C.S),12274061(to L.Q.)]Key Research and Development Program from the Ministry of Science and Technology(2023YFA1406301)the support from the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘The infinite-layer nickelates,proposed as analogs to superconducting cuprates,provide a promising platform for exploring the mechanisms of unconventional superconductivity.However,the superconductivity has been exclusively observed in thin films under atmospheric pressure,underscoring the critical role of the heterointerface.
基金the National Key R&D Program of China(Grant No.2019YFA0708200)the National Natural Science Foundation of China(Grant Nos.52125307,11974023,12104017,and 52021006)+1 种基金the“2011 Program”from the Peking-Tsinghua-IOP Collaborative Innovation Center of Quantum MatterYouth Innovation Promotion Association,CAS。
文摘Phonons are the primary heat carriers in non-metallic solids.In compositionally heterogeneous materials,the thermal properties are believed to be mainly governed by the disrupted phonon transport due to mass disorder and strain fluctuations,while the effects of compositional fluctuation induced local phonon states are usually ignored.Here,by scanning transmission electron microscopy electron energy loss spectroscopy and sophisticated calculations,we identify the vibrational properties of ingredient-dependent interface phonon modes in Alx Ga1-x N and quantify their various contributions to the local interface thermal conductance.We demonstrate that atomic-scale compositional fluctuation has significant influence on the vibrational thermodynamic properties,highly affecting the mode ratio and vibrational amplitude of interface phonon modes and subsequently redistributing their modal contribution to the interface thermal conductance.Our work provides fundamental insights into understanding of local phonon-boundary interactions in nanoscale inhomogeneities,which reveal new opportunities for optimization of thermal properties via engineering ingredient distribution.
文摘The law of language learning has a theoretical basis.Language learning is a process of active learning,not of passive acceptance.Situational teaching is the extension and development of constructivist teaching.The correct use of situational teaching can stimulate students 125 interest,facilitate a harmonious relationship between teachers and students,as well as promote the cultivation of other skills among students,so as to improve the teaching quality of oral Chinese teaching as a foreign language and effectively complete the teaching task.However,there are some issues that should be emphasized when using the situational teaching method,such as how to create situations effectively,the problems that teachers should pay attention to when creating situations,and the principles of creating situations.
基金We gratefully acknowledge the support from the“2011 Program”Peking-Tsinghua-IOP,China Collaborative Innovation Center of Quantum Matter.The authors acknowledge Electron Microscopy Laboratory of Peking University,China for the use of Cs corrected electron microscope.This work was supported by the National Natural Science Foundation of China(11974023,51672007)the National Key R&D Program of China(2016YFA0300804)+1 种基金the National Equipment Program of China(ZDYZ2015-1)the Key-Area Research and Development Program of Guangdong Provience(2018B030327001,2018B010109009).
文摘Surface phonon polaritons(SPh Ps) are potentially very attractive for subwavelength control and manipulation of light at the infrared to terahertz wavelengths. Probing their propagation behavior in nanostructures is crucial to guide rational device design. Here, aided by monochromatic scanning transmission electron microscopy-electron energy loss spectroscopy technique, we measure the dispersion relation of SPh Ps in individual Si C nanorods and reveal the effects of size and shape. We find that the SPh Ps can be modulated by the geometric shape and size of Si C nanorods. The energy of SPh Ps shows redshift with decreasing radius and the surface optical phonon is mainly concentrated on the surface with large radius. Therefore, the fields can be precisely confined in specific positions by varying the size of the nanorod, allowing effective tuning at nanometer scale. The findings of this work are in agreement with dielectric response theory and numerical simulation, and provide novel strategies for manipulating light in polar dielectrics through shape and size control, enabling the design of novel nanoscale phononphotonic devices.
基金supported by the National Basic Research Program of China(2016YFA0300804)the National Natural Science Foundation of China(51672007 and 11974023)+6 种基金Key Area R&D Program of Guangdong Province(2018B010109009)the Key R&D Program of Guangdong Province(2018B030327001)National Equipment Program of China(ZDYZ2015-1)the‘‘2011 Program”Peking-Tsinghua-IOP Collaborative Innovation Centre for Quantum Mattersupported by the National Basic Research Program of China(2016YFA0301004)the National Natural Science Foundation of China(51872155,52025024)the Beijing Advanced Innovation Center for Future Chip(ICFC)。
文摘Confined low dimensional charges with high density such as two-dimensional electron gas(2 DEG)at interfaces and charged domain walls in ferroelectrics show great potential to serve as functional elements in future nanoelectronics.However,stabilization and control of low dimensional charges is challenging,as they are usually subject to enormous depolarization fields.Here,we demonstrate a method to fabricate tunable charged interfaces with~77°,86°and 94°head-to-head polarization configurations in multiferroic Bi Fe O_(3) thin films by grain boundary engineering.The adjacent grains are cohesively bonded and the boundary is about 1 nm in width and devoid of any amorphous region.Remarkably,the polarization remains almost unchanged near the grain boundaries,indicating the polarization charges are well compensated,i.e.,there should be two-dimensional charge gas confined at grain boundaries.Adjusting the tilt angle of the grain boundaries enables tuning the angle of polarization configurations from 71°to 109°,which in turn allows the control of charge density at the grain boundaries.This general and feasible method opens new doors for the application of charged interfaces in next generation nanoelectronics.
