We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blu...We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.展开更多
To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,...To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,Al-Al and Cu-Cu combinations fabricated through collision welding using molecular dynamic(MD)simulation.The atomic diffusion behaviors are compared between similar metal combinations(Al-Al,Cu-Cu)and dissimilar metal combinations(Al-Cu).By combining the simulation results and classical diffusion theory,the diffusion coefficients for similar and dissimilar metal material combinations under different velocity conditions are obtained.The effects of material combinations and collision velocity on diffusion behaviors are also discussed.The diffusion behaviors of dissimilar material combinations strongly depend on the transverse velocity,whereas those of the similar material combinations are more dependent on the longitudinal velocity.These findings can provide guidance for optimizing welding parameters.展开更多
It is urgent to establish a series of reasonable and general approaches to qualitatively and graphically characterize the four core effects of multi-principal element alloys(MPEAs)based on the inherent site preference...It is urgent to establish a series of reasonable and general approaches to qualitatively and graphically characterize the four core effects of multi-principal element alloys(MPEAs)based on the inherent site preference.In this contribution,a qualitatively and graphically characterizing approach to the diffusion behavior of interstitial nonmetallic atoms diffusing along the neighboring octahedra in MPEAs was explored intensively.For this purpose,the C atom diffusing along the neighboring octahedra in FCC_CoNiV MPEA with(V1.0000)1a(Co0.4445Ni0.4444V0.1111)3c,a constant ordered occupying configuration predicted in our previous paper,was demonstrated in detail.Six distinct diffusion paths along[110],[101],and[011]directions on XY,XZ,and YZ planes of FCC_CoNiV MPEA with forward and backward diffusion directions were explored one by one,respectively.The diffusion energy barrier,diffusion coefficient,diffusion constant,and activation energy were derived by employing first-principles calculations based on density functional theory alongside the Climbing Image Nudged Elastic Band method.Unlike diffusing behavior in pure metallic elements,the non-periodic diffusion energy barrier waves are revealed for the real FCC_CoNiV MPEA structure.The significant variations in the diffusion energy barriers are influenced by the atomic environment,particularly the interaction between V and C atoms,which enhances the localization of electrons and increases the overall diffusion energy barrier.The energy barriers show similar trends along six paths,but significant variations occur across different octahedral sites.展开更多
In this Letter, we focus on the theoretical analysis of the relativistic energy and angular distributions of the ejected photoelectrons during the relativistic tunnel ionization of atoms by intense, circularly polariz...In this Letter, we focus on the theoretical analysis of the relativistic energy and angular distributions of the ejected photoelectrons during the relativistic tunnel ionization of atoms by intense, circularly polarized light. We make a small modification of the general analytical expressions for these distributions. The role of the initial momentum, the ponderomotive potential, and the Stark shift are considered. We also present the maximal angle of electron emission.展开更多
Amorphous and non-stoichiometric hafnium oxide(a-HfO_(x))systems are essential for advanced electronic applications due to their superior electrical properties.Simulating their atomic behaviors under electric fields(E...Amorphous and non-stoichiometric hafnium oxide(a-HfO_(x))systems are essential for advanced electronic applications due to their superior electrical properties.Simulating their atomic behaviors under electric fields(Efield)is critical but challenging.Ab-initio molecular dynamics(AIMD)offer high accuracy but is computationally expensive,while classical MD lacks precision.To address this,we develop a charge equilibration integrated graph neural network(CIGNN)model that predicts atomic charge,energy,and force under Efield conditions.Using the CIGNN model and AIMD datasets,we develop a CIGNN-based machine learning potential(CNMP)optimized for a-HfO_(x)systems.The CNMP achieves quantum mechanical accuracy and effectively captures the atomic behaviors and dynamic properties of these systems across varying temperatures,densities,and E_(field)conditions.We expect the CNMP to serve as a valuable tool for studying field-induced phenomena in complex systems and to provide a foundation for advancing innovations in electronic applications.展开更多
By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The ...By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance（NDR） behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into m V bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.展开更多
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0301503the National Natural Science Foundation of China under Grant Nos 11674358 and 11434015the Instrument Project of the Chinese Academy of Sciences under Grant No YJKYYQ20170025
文摘We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.
基金supported by the Scientific Research Project of Hunan Provincial Department of Education(22C0642).
文摘To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,Al-Al and Cu-Cu combinations fabricated through collision welding using molecular dynamic(MD)simulation.The atomic diffusion behaviors are compared between similar metal combinations(Al-Al,Cu-Cu)and dissimilar metal combinations(Al-Cu).By combining the simulation results and classical diffusion theory,the diffusion coefficients for similar and dissimilar metal material combinations under different velocity conditions are obtained.The effects of material combinations and collision velocity on diffusion behaviors are also discussed.The diffusion behaviors of dissimilar material combinations strongly depend on the transverse velocity,whereas those of the similar material combinations are more dependent on the longitudinal velocity.These findings can provide guidance for optimizing welding parameters.
基金supported by the National Natural Science Foundation of China(50971043 and 51171046)the Key Research and Development Program of China(CISRI-21T62450ZD)+1 种基金the Natural Science Foundation of Fujian Province(2014J01176,2018J01754,and 2021J01590)the Student Research and Training Program(SRTP)of Fuzhou University(27297).
文摘It is urgent to establish a series of reasonable and general approaches to qualitatively and graphically characterize the four core effects of multi-principal element alloys(MPEAs)based on the inherent site preference.In this contribution,a qualitatively and graphically characterizing approach to the diffusion behavior of interstitial nonmetallic atoms diffusing along the neighboring octahedra in MPEAs was explored intensively.For this purpose,the C atom diffusing along the neighboring octahedra in FCC_CoNiV MPEA with(V1.0000)1a(Co0.4445Ni0.4444V0.1111)3c,a constant ordered occupying configuration predicted in our previous paper,was demonstrated in detail.Six distinct diffusion paths along[110],[101],and[011]directions on XY,XZ,and YZ planes of FCC_CoNiV MPEA with forward and backward diffusion directions were explored one by one,respectively.The diffusion energy barrier,diffusion coefficient,diffusion constant,and activation energy were derived by employing first-principles calculations based on density functional theory alongside the Climbing Image Nudged Elastic Band method.Unlike diffusing behavior in pure metallic elements,the non-periodic diffusion energy barrier waves are revealed for the real FCC_CoNiV MPEA structure.The significant variations in the diffusion energy barriers are influenced by the atomic environment,particularly the interaction between V and C atoms,which enhances the localization of electrons and increases the overall diffusion energy barrier.The energy barriers show similar trends along six paths,but significant variations occur across different octahedral sites.
基金supported by the Serbian Ministry of Education,Science,and Technological Development for financial support through Projects 171020 and 171021
文摘In this Letter, we focus on the theoretical analysis of the relativistic energy and angular distributions of the ejected photoelectrons during the relativistic tunnel ionization of atoms by intense, circularly polarized light. We make a small modification of the general analytical expressions for these distributions. The role of the initial momentum, the ponderomotive potential, and the Stark shift are considered. We also present the maximal angle of electron emission.
基金supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning No. NRF-2020R1A6C101A202 and NRF-2024M3A7C2045166 and NRF-2021M3I3A1084940 and RS-2023-00257666 and RS-2024-00446683 and RS-2024-00450836.
文摘Amorphous and non-stoichiometric hafnium oxide(a-HfO_(x))systems are essential for advanced electronic applications due to their superior electrical properties.Simulating their atomic behaviors under electric fields(Efield)is critical but challenging.Ab-initio molecular dynamics(AIMD)offer high accuracy but is computationally expensive,while classical MD lacks precision.To address this,we develop a charge equilibration integrated graph neural network(CIGNN)model that predicts atomic charge,energy,and force under Efield conditions.Using the CIGNN model and AIMD datasets,we develop a CIGNN-based machine learning potential(CNMP)optimized for a-HfO_(x)systems.The CNMP achieves quantum mechanical accuracy and effectively captures the atomic behaviors and dynamic properties of these systems across varying temperatures,densities,and E_(field)conditions.We expect the CNMP to serve as a valuable tool for studying field-induced phenomena in complex systems and to provide a foundation for advancing innovations in electronic applications.
基金Project supported by the National Natural Science Foundation of China(No.11274096)the University Science and Technology Innovation Team Support Project of Henan Province(No.13IRTSTHN016)+1 种基金the University key Science Research Project of Henan Province(No.16A140043)supported by the High Performance Computing Center of Henan Normal University
文摘By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance（NDR） behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into m V bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.
