Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graph...Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.展开更多
Energies for the ground states of double electron systems in a uniform magnetic field B≤ 10 9 G are calculated by using the modified Slater basis and configuration interaction method, and the result for energy i...Energies for the ground states of double electron systems in a uniform magnetic field B≤ 10 9 G are calculated by using the modified Slater basis and configuration interaction method, and the result for energy in zero magnetic field is comparable with those obtained by different methods.展开更多
The AlGaN-based deep ultraviolet light-emitting diodes（LED） with double electron blocking layers（d-EBLs） on both sides of the active region are investigated theoretically. They possess many excellent performances ...The AlGaN-based deep ultraviolet light-emitting diodes（LED） with double electron blocking layers（d-EBLs） on both sides of the active region are investigated theoretically. They possess many excellent performances compared with the conventional structure with only a single electron blocking layer, such as a higher recombination rate, improved light output power and internal quantum efficiency（IQE）. The reasons can be concluded as follows. On the one hand, the weakened electrostatic field within the quantum wells（QWs） enhances the electron–hole spatial overlap in QWs, and therefore increases the probability of radioactive recombination. On the other hand, the added n-AlGaN layer can not only prevent holes from overflowing into the n-side region but also act as another electron source, providing more electrons.展开更多
A novel A1GaN/GaN high electron mobility transistor （HEMT） with double buried p-type layers （DBPLs） in the GaN buffer layer and its mechanism are studied. The DBPL A1GaN/GaN HEMT is characterized by two equi-long ...A novel A1GaN/GaN high electron mobility transistor （HEMT） with double buried p-type layers （DBPLs） in the GaN buffer layer and its mechanism are studied. The DBPL A1GaN/GaN HEMT is characterized by two equi-long p-type GaN layers which are buried in the GaN buffer layer under the source side. Under the condition of high-voltage blocking state, two reverse p-n junctions introduced by the buried p-type layers will effectively modulate the surface and bulk electric fields. Meanwhile, the buffer leakage is well suppressed in this structure and both lead to a high breakdown voltage. The simulations show that the breakdown voltage of the DBPL structure can reach above 2000 V from 467 V of the conventional structure with the same gate-drain length of 8μm.展开更多
Electron correlation is encoded directly in the distribution of the energetic electrons produced in a recollision-impact double ionization process, and varies with the laser field and the target atoms. In order to get...Electron correlation is encoded directly in the distribution of the energetic electrons produced in a recollision-impact double ionization process, and varies with the laser field and the target atoms. In order to get equivalent electron correlation effects, one should enlarge the laser intensity cubically and the laser frequency linearly in proportion to the second ionization potentials of the target atoms. The physical mechanism behind the transform is to keep the ponderomotive parameter unchanged when the laser frequency is enlarged.展开更多
The structural, magnetic and electronic properties of the double perovskite Ba2SmNbO6 （for the simple cubic structure where no octahedral tilting exists anymore） are studied using the density functional theory withi...The structural, magnetic and electronic properties of the double perovskite Ba2SmNbO6 （for the simple cubic structure where no octahedral tilting exists anymore） are studied using the density functional theory within the generalized gradient approximation as well as taking into account the on-site Coulomb repulsive interaction. The total energy, the spin magnetic moment, the band structure and the density of states are calculated. The optimization of the lattice constants is 8.5173 A, which is in good agreement with the experimental value 8.5180 A. The calculations reveal that Ba2SmNbO6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is 5.00μB/f.u. which comes mostly from the Sin3＋ ion only. By analysis of the band structure, the compound exhibits the direct band gap material and half-metallic ferromagnetic nature with 100% spin-up polarization, which implies potential applications of this new lanthanide compound in magneto-electronic and spintronic devices.展开更多
Some realizable structures of double parabolic quantum wells（DPQWs） consisting of Al_xGa_（1-x）As/Al_yGa_（1-y）As are constructed to discuss theoretically the optical absorption due to the intersubband transition ...Some realizable structures of double parabolic quantum wells（DPQWs） consisting of Al_xGa_（1-x）As/Al_yGa_（1-y）As are constructed to discuss theoretically the optical absorption due to the intersubband transition of electrons for both symmetric and asymmetric cases with three energy levels of conduction bands. The electronic states in these structures are obtained using a finite element difference method. Based on a compact density matrix approach, the optical absorption induced by intersubband transition of electrons at room temperature is discussed. The results reveal that the peak positions and heights of intersubband optical absorption coefficients（IOACs） of DPQWs are sensitive to the barrier thickness, depending on Al component. Furthermore, external electric fields result in the decrease of peak, and play an important role in the blue shifts of absorption spectra due to electrons excited from ground state to the first and second excited states. It is found that the peaks of IOACs are smaller in asymmetric DPQWs than in symmetric ones. The results also indicate that the adjustable extent of incident photon energy for DPQW is larger than for a square one of a similar size. Our results are helpful in experiments and device fabrication.展开更多
[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,...[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.展开更多
In the present investigation,twinned substructures within lath martensite of two water quenched steels(0.2 wt.%C and 0.8 wt.%C)were studied.The lath martensite has typical hierarchical packet-block-lath with dislocati...In the present investigation,twinned substructures within lath martensite of two water quenched steels(0.2 wt.%C and 0.8 wt.%C)were studied.The lath martensite has typical hierarchical packet-block-lath with dislocation substructure.Besides,laths that are misoriented by<011>/70.5°or<111>/60° and bordered by{011}plane,namely twinned laths,are observed,of which the density increases and the scale decreases as more carbons were presented.Such twinned laths have body centered cubic(bcc)crystal structure,belonging to twinned variants following the classical Kurdjumov-Sachs(K-S)orientation relationship with respect to the parent austenite.Unlike bcc{112}<111>twins,twinned variants produce strong double diffraction and in turn the extra diffraction spots that are commonly observed in the martensite in steels with wide range of carbon contents.展开更多
Electronic speckle pattern interferometry（ESPI） and digital speckle pattern interferometry are wellestablished non-contact measurement methods. They have been widely used to carry out precise deformation mapping. Ho...Electronic speckle pattern interferometry（ESPI） and digital speckle pattern interferometry are wellestablished non-contact measurement methods. They have been widely used to carry out precise deformation mapping. However, the simultaneous two-dimensional（2D） or three-dimensional（3D） deformation measurements using ESPI with phase shifting usually involve complicated and slow equipment. In this Letter, we solve these issues by proposing a modified ESPI system based on double phase modulations with only one laser and one camera. In-plane normal and shear strains are obtained with good quality. This system can also be developed to measure 3D deformation, and it has the potential to carry out faster measurements with a highspeed camera.展开更多
A three-dimensional model of GaAs/A1GaAs quantum double rings in the lateral static electric field is investigated theoretically. The eigenvalue problem with the effective-mass approximation is solved by means of the ...A three-dimensional model of GaAs/A1GaAs quantum double rings in the lateral static electric field is investigated theoretically. The eigenvalue problem with the effective-mass approximation is solved by means of the finite-element method. The energy levels and wave functions of quantum-confined electrons and heavy holes are obtained and show an agreement with our previous theoretical and experimental studies. It is shown in the approximation of neglecting the Coulomb attraction between the electron and heavy hole that a relatively large Stark shift of exciton emission of 4 meV is attainable with an applied electric field of 0.7 kV/cm.展开更多
The discovery of fluorescence materials with an inverted singlet-triplet(IST)energy gap,where the singlet excited state(S_(1))lies below the triplet excited state(T_(1)),mark a transformative advancement in organic li...The discovery of fluorescence materials with an inverted singlet-triplet(IST)energy gap,where the singlet excited state(S_(1))lies below the triplet excited state(T_(1)),mark a transformative advancement in organic light-emitting diodes(OLEDs)technology.However,designing the potential IST emitters are greatly challenging,and their IST energy gap,arising from double electron excitation,can only be accurately described by time-consuming post-Hartree-Fock(HF)methods,which blocks large-scale high-throughput screening speed.Here,we develop a four-orbital model to elucidate detailly the roles of double excitations in the IST formation,and establish two molecular descriptors(K_(S)and O_(D))based on exchange integral and molecular orbital energy.By these descriptors,we rapidly identify 41 IST candidates out of 3,486 molecules.The descriptors-aided approach achieves a screening success rate of 90%and reduces computational costs by 13 times compared to full post-HF calculations.Importantly,wepredicted a series of excellent non-traditional near-infrared IST emitters from a dataset of 1028 compounds with emission wavelengths ranging from 852.2 to 1002.3 nm,which open new avenues for designing highly efficient near-infrared OLED materials.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12474051 and 92165201)the Chinese Academy of Sciences Project for Young Scientists in Basic Research (Grant No.YSBR-046)+1 种基金the National Key Research and Development Program of China (Grant No.2023YFA1406300)the Anhui Provincial Natural Science Foundation (Grant Nos.2308085J11 and2308085QA14)。
文摘Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.
文摘Energies for the ground states of double electron systems in a uniform magnetic field B≤ 10 9 G are calculated by using the modified Slater basis and configuration interaction method, and the result for energy in zero magnetic field is comparable with those obtained by different methods.
基金Project supported by the Special Strategic Emerging Industries of Guangdong Province,China(Grant No.2012A080304006)the Major Scientific and Technological Projects of Zhongshan City,Guangdong Province,China(Grant No.2014A2FC204)the Forefront of Technology Innovation and Key Technology Projects of Guangdong Province,China(Grant Nos.2014B010121001 and 2014B010119004)
文摘The AlGaN-based deep ultraviolet light-emitting diodes（LED） with double electron blocking layers（d-EBLs） on both sides of the active region are investigated theoretically. They possess many excellent performances compared with the conventional structure with only a single electron blocking layer, such as a higher recombination rate, improved light output power and internal quantum efficiency（IQE）. The reasons can be concluded as follows. On the one hand, the weakened electrostatic field within the quantum wells（QWs） enhances the electron–hole spatial overlap in QWs, and therefore increases the probability of radioactive recombination. On the other hand, the added n-AlGaN layer can not only prevent holes from overflowing into the n-side region but also act as another electron source, providing more electrons.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61334002,61106106,and 61204085the China Postdoctoral Science Foundation Funded Project under Grant No 2015M582610
文摘A novel A1GaN/GaN high electron mobility transistor （HEMT） with double buried p-type layers （DBPLs） in the GaN buffer layer and its mechanism are studied. The DBPL A1GaN/GaN HEMT is characterized by two equi-long p-type GaN layers which are buried in the GaN buffer layer under the source side. Under the condition of high-voltage blocking state, two reverse p-n junctions introduced by the buried p-type layers will effectively modulate the surface and bulk electric fields. Meanwhile, the buffer leakage is well suppressed in this structure and both lead to a high breakdown voltage. The simulations show that the breakdown voltage of the DBPL structure can reach above 2000 V from 467 V of the conventional structure with the same gate-drain length of 8μm.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61475168 and 11674231)sponsored by Shanghai Gaofeng&Gaoyuan Project for University Academic Program Development(Zhang)
文摘Electron correlation is encoded directly in the distribution of the energetic electrons produced in a recollision-impact double ionization process, and varies with the laser field and the target atoms. In order to get equivalent electron correlation effects, one should enlarge the laser intensity cubically and the laser frequency linearly in proportion to the second ionization potentials of the target atoms. The physical mechanism behind the transform is to keep the ponderomotive parameter unchanged when the laser frequency is enlarged.
文摘The structural, magnetic and electronic properties of the double perovskite Ba2SmNbO6 （for the simple cubic structure where no octahedral tilting exists anymore） are studied using the density functional theory within the generalized gradient approximation as well as taking into account the on-site Coulomb repulsive interaction. The total energy, the spin magnetic moment, the band structure and the density of states are calculated. The optimization of the lattice constants is 8.5173 A, which is in good agreement with the experimental value 8.5180 A. The calculations reveal that Ba2SmNbO6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is 5.00μB/f.u. which comes mostly from the Sin3＋ ion only. By analysis of the band structure, the compound exhibits the direct band gap material and half-metallic ferromagnetic nature with 100% spin-up polarization, which implies potential applications of this new lanthanide compound in magneto-electronic and spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.61274098)
文摘Some realizable structures of double parabolic quantum wells（DPQWs） consisting of Al_xGa_（1-x）As/Al_yGa_（1-y）As are constructed to discuss theoretically the optical absorption due to the intersubband transition of electrons for both symmetric and asymmetric cases with three energy levels of conduction bands. The electronic states in these structures are obtained using a finite element difference method. Based on a compact density matrix approach, the optical absorption induced by intersubband transition of electrons at room temperature is discussed. The results reveal that the peak positions and heights of intersubband optical absorption coefficients（IOACs） of DPQWs are sensitive to the barrier thickness, depending on Al component. Furthermore, external electric fields result in the decrease of peak, and play an important role in the blue shifts of absorption spectra due to electrons excited from ground state to the first and second excited states. It is found that the peaks of IOACs are smaller in asymmetric DPQWs than in symmetric ones. The results also indicate that the adjustable extent of incident photon energy for DPQW is larger than for a square one of a similar size. Our results are helpful in experiments and device fabrication.
基金National Key Research and Development Program of China(2022YFF0707602)National Natural Science Foundation of China(62471097,62471115,62471101)National Natural Science Foundation of Sichuan(2025ZNSFSC0537)。
文摘[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.
基金supported financially by the Hundred Outstanding Creative Talents Projects in Hebei University,Chinathe Project Program of Heavy Machinery Collaborative Innovation Center,the National Natural Science Foundation(Grant No.51231006,51171182 and 51471039)。
文摘In the present investigation,twinned substructures within lath martensite of two water quenched steels(0.2 wt.%C and 0.8 wt.%C)were studied.The lath martensite has typical hierarchical packet-block-lath with dislocation substructure.Besides,laths that are misoriented by<011>/70.5°or<111>/60° and bordered by{011}plane,namely twinned laths,are observed,of which the density increases and the scale decreases as more carbons were presented.Such twinned laths have body centered cubic(bcc)crystal structure,belonging to twinned variants following the classical Kurdjumov-Sachs(K-S)orientation relationship with respect to the parent austenite.Unlike bcc{112}<111>twins,twinned variants produce strong double diffraction and in turn the extra diffraction spots that are commonly observed in the martensite in steels with wide range of carbon contents.
基金financially supported by the ANR Micromorfing Program(ANR-14-CE07-0035)China Scholarship Council(CSC)the Labex Action
文摘Electronic speckle pattern interferometry（ESPI） and digital speckle pattern interferometry are wellestablished non-contact measurement methods. They have been widely used to carry out precise deformation mapping. However, the simultaneous two-dimensional（2D） or three-dimensional（3D） deformation measurements using ESPI with phase shifting usually involve complicated and slow equipment. In this Letter, we solve these issues by proposing a modified ESPI system based on double phase modulations with only one laser and one camera. In-plane normal and shear strains are obtained with good quality. This system can also be developed to measure 3D deformation, and it has the potential to carry out faster measurements with a highspeed camera.
基金supported by a Grant-in-Aid for Scientific Research from the Ministry of Education,Science,Sports,and Culture of Japan (No.20340080).
文摘A three-dimensional model of GaAs/A1GaAs quantum double rings in the lateral static electric field is investigated theoretically. The eigenvalue problem with the effective-mass approximation is solved by means of the finite-element method. The energy levels and wave functions of quantum-confined electrons and heavy holes are obtained and show an agreement with our previous theoretical and experimental studies. It is shown in the approximation of neglecting the Coulomb attraction between the electron and heavy hole that a relatively large Stark shift of exciton emission of 4 meV is attainable with an applied electric field of 0.7 kV/cm.
基金support from the National Natural Science Foundation of China(Grant Nos.22325305 and 22273105)the Strategic Priority Research Program of Sciences(XDB0520103)+1 种基金National Key R&D Program of China(2024YFB3614300)the Fundamental Research Funds for the Central Universities(Grant Nos.E2E40307X2 and E2ET0309X2).We gratefully acknowledge WQ&UCAS Research Academy Intelligent Computing Center(WRA-ICC)for providing computation facilities.
文摘The discovery of fluorescence materials with an inverted singlet-triplet(IST)energy gap,where the singlet excited state(S_(1))lies below the triplet excited state(T_(1)),mark a transformative advancement in organic light-emitting diodes(OLEDs)technology.However,designing the potential IST emitters are greatly challenging,and their IST energy gap,arising from double electron excitation,can only be accurately described by time-consuming post-Hartree-Fock(HF)methods,which blocks large-scale high-throughput screening speed.Here,we develop a four-orbital model to elucidate detailly the roles of double excitations in the IST formation,and establish two molecular descriptors(K_(S)and O_(D))based on exchange integral and molecular orbital energy.By these descriptors,we rapidly identify 41 IST candidates out of 3,486 molecules.The descriptors-aided approach achieves a screening success rate of 90%and reduces computational costs by 13 times compared to full post-HF calculations.Importantly,wepredicted a series of excellent non-traditional near-infrared IST emitters from a dataset of 1028 compounds with emission wavelengths ranging from 852.2 to 1002.3 nm,which open new avenues for designing highly efficient near-infrared OLED materials.
