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Optical study of magnetic topological insulator MnBi_(4)Te_7
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作者 廖知裕 沈冰 +1 位作者 邱祥冈 许兵 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期231-235,共5页
We present an infrared spectroscopy study of the magnetic topological insulator MnBi_(4)Te_7 with antiferromagnetic(AFM) order below the Neel temperature TN= 13 K. Our investigation reveals that the low-frequency opti... We present an infrared spectroscopy study of the magnetic topological insulator MnBi_(4)Te_7 with antiferromagnetic(AFM) order below the Neel temperature TN= 13 K. Our investigation reveals that the low-frequency optical conductivity consists of two Drude peaks, indicating a response of free carriers involving multiple bands. Interestingly, the narrow Drude peak grows strongly as the temperature decreases, while the broad Drude peak remains relatively unchanged. The onset of interband transitions starts around 2000 cm^(-1), followed by two prominent absorption peaks around 10000 cm^(-1) and 20000 cm^(-1). Upon cooling, there is a notable transfer of spectral weight from the interband transitions to the Drude response. Below TN, the AFM transition gives rise to small anomalies of the charge response due to a band reconstruction.These findings provide valuable insights into the interplay between magnetism and the electronic properties in MnBi_(4)Te_7. 展开更多
关键词 infrared spectroscopy magnetic topological insulator Drude model band reconstruction
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Optical spectrum of ferrovalley materials:A case study of Janus H-VSSe
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作者 罗朝波 刘文超 彭向阳 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期54-59,共6页
As opposed to the prototypical MoS2 with centroasymmetry,Janus ferrovalley materials such as H-VSSe are less symmetric with the mirror symmetry and time reversal symmetry broken,and hence possess spontaneous valley po... As opposed to the prototypical MoS2 with centroasymmetry,Janus ferrovalley materials such as H-VSSe are less symmetric with the mirror symmetry and time reversal symmetry broken,and hence possess spontaneous valley polarization and strong ferroelasticity.The optical transition is an important means to excite the valley carriers.We investigate the optical spectrum of H-VSSe by using the many-body perturbation-based GW approach and solving the Bethe–Salpeter equation(BSE)to include the electron–hole interactions.It is found that after the GW correction,the band gaps of the quasiparticle bands are much larger than those obtained by the normal density functional theory.The system is ferromagnetic and the valley gaps become non-degenerate due to spin–orbit coupling(SOC).The position of the lowest BSE peak is much lower than the quasiparticle band gap,indicating that the excitonic effect is large.The peak is split into two peaks by the SOC.The binding energy difference between these two BSE peaks is about the same as the difference between the inequivalent valley gaps.Our results show that in Janus H-VSSe the two lowest exciton peaks are from the two inequivalent valleys with different gaps,in contrast to the A and B exciton peaks of MoS2 which are from the same valley. 展开更多
关键词 infrared spectroscopy magnetic topological insulator Drude model band reconstruction
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Relationship between disorder,magnetism and band topology in Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals
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作者 席明 雷和畅 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第6期102-107,共6页
We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It... We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥0.25.Further analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these systems.With the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground state.In addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples. 展开更多
关键词 magnetic topological insulator magnetic properties antisite defects chemical vapor transport
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Investigation of an X-band magnetically insulated transmission line oscillator 被引量:4
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作者 樊玉伟 钟辉煌 +6 位作者 李志强 舒挺 杨汉武 杨建华 王勇 罗玲 赵延宋 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第5期1804-1808,共5页
An X-band magnetically insulated transmission line oscillator (MILO) is designed and investigated numerically and experimentally for the first time. The X-band MILO is optimized in detail with KARAT code. In simulat... An X-band magnetically insulated transmission line oscillator (MILO) is designed and investigated numerically and experimentally for the first time. The X-band MILO is optimized in detail with KARAT code. In simulation, the X-band MILO, driven by a 720 kV, 53 kA electron beam, comes to a nonlinear steady state in 4.0 ns. High-power microwaves (HPM) of TEM mode is generated with an average power of 4.1 GW, a frequency of 9.3 GHz, and power conversion efficiency of 10.870 in durations of 0-40 ns. The device is fabricated according to the simulation results. In experiments, when the voltage is 400 kV and the current is 50 kA, the radiated microwave power reaches about 110 MW and the dominating frequency is 9.7GHz. Because the surfaces of the cathode end and the beam dump are destroyed, the diode voltage cannot increase continuously. However, when the diode voltage is 400 kV, the average power output is obtained to be 700 MW in simulation. The impedance of the device is clearly smaller than the simulation prediction. Moreover, the duration of the microwave pulse is obviously shorter than that of the current pulse. The experimental results are greatly different from the simulation predictions. The preliminary analyses show that the generations of the anode plasma, the cathode flare and the anode flare are the essential cause for the remarkable deviation of the experimental results from the simulation predictions. 展开更多
关键词 magnetically insulated transmission line oscillator (MILO) high-power microwaves(HPM) pulse shortening
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Experimental Study of Current Loss of Stainless Steel Magnetically Insulated Transmission Line with Current Density at MA/cm Level 被引量:2
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作者 吴撼宇 曾正中 +1 位作者 王亮平 郭宁 《Plasma Science and Technology》 SCIE EI CAS CSCD 2014年第6期625-628,共4页
A magnetically insulated transmission line (MITL) is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/... A magnetically insulated transmission line (MITL) is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL. 展开更多
关键词 magnetically insulated transmission line current loss current density ION
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Simulation of the effect of a magnetically insulated anode on a low-power cylindrical Hall thruster 被引量:1
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作者 Yongjie DING Hong LI +7 位作者 Boyang JIA Peng LI Liqiu WEI Yu XU Wuji PENG Hezhi SUN Yong CAO Daren YU 《Plasma Science and Technology》 SCIE EI CAS CSCD 2018年第3期156-162,共7页
The intersection point of the characteristic magnetic field line(CMFL) crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombardin... The intersection point of the characteristic magnetic field line(CMFL) crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombarding the channel wall, have been studied numerically. The simulation results demonstrate that with the increase in distance from the crossover point of the CMFL with the channel wall to the bottom of the thruster channel, the ionization rate in the discharge channel gradually increases; meanwhile, the ion energy and ion current density bombarding the channel wall decreases. When the point of the CMFL with the channel wall is at the channel outlet, the thrust, specific impulse, and efficiency are at a maximum, while the ion energy and ion current density bombarding the channel wall are at a minimum. Therefore, to improve the performance and lifetime of the thruster, it is important to control the point of intersection of the CMFL with the channel wall. 展开更多
关键词 magnetically insulated anode cylindrical Hall thruster PERFORMANCE
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Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator 被引量:4
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作者 Nansha Gao Hong Hou Yihao Mu 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2017年第4期252-257,共6页
A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequenc... A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis(FEA) results agree well with the experimental results.It is proved that the sound transmission losses(STLs) of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control. 展开更多
关键词 Bilayer membrane acoustic metamaterial Low frequency sound insulation Sound transmission loss Magnet oscillator
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The origin of spin current in YIG/nonmagnetic metal multilayers at ferromagnetic resonance
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作者 康韵 钟海 +11 位作者 郝润润 胡树军 康仕寿 刘国磊 张引 王向荣 颜世申 吴勇 于淑云 韩广兵 姜勇 梅良模 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第4期388-397,共10页
Spin pumping in yttrium-iron-garnet(YIG)/nonmagnetic-metal(NM) layer systems under ferromagnetic resonance(FMR) conditions is a popular method of generating spin current in the NM layer.A good understanding of t... Spin pumping in yttrium-iron-garnet(YIG)/nonmagnetic-metal(NM) layer systems under ferromagnetic resonance(FMR) conditions is a popular method of generating spin current in the NM layer.A good understanding of the spin current source is essential in extracting spin Hall angle of the NM and in potential spintronics applications.It is widely believed that spin current is pumped from precessing YIG magnetization into NM layer.Here,by combining microwave absorption and DC-voltage measurements on thin YIG/Pt and YIG/NM_1/NM_2(NM_1 =Cu or Al,NM_2 =Pt or Ta),we unambiguously showed that spin current in NM,instead of from the precessing YIG magnetization,came from the magnetized NM surface(in contact with thin YIG),either due to the magnetic proximity effect(MPE) or from the inevitable diffused Fe ions from YIG to NM.This conclusion is reached through analyzing the FMR microwave absorption peaks with the DC-voltage peak from the inverse spin Hall effect(ISHE).The voltage signal is attributed to the magnetized NM surface,hardly observed in the conventional FMR experiments,and was greatly amplified when the electrical detection circuit was switched on. 展开更多
关键词 spin current spin pumping inverse spin Hall effect magnetic proximity effect magnetic insulator
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Magnetically insulated transmission line oscillator oscillated in a modified HEM_(11) mode
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作者 王冬 陈代兵 +1 位作者 秦奋 范植开 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第10期4281-4286,共6页
This paper puts forward a novel magnetically insulated transmission line oscillator (MILO) for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is... This paper puts forward a novel magnetically insulated transmission line oscillator (MILO) for the first time which takes a modified HEM11 mode as its main interaction mode. The excitation of the oscillation mode is made possible by carefully adjusting the arrangements of each resonant cavity in a two-dimensional (2-D) slow wave structure. The high frequency characteristics are analyzed and a PIC simulation is carried out; the detailed results are discussed to get a better understanding of this new MILO. Employing an electron beam of about 441 kV and 39.7 kA, it finds that the modified HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz. The power conversion efficiency is about 8.4% and the generated microwave is in a TEll-like circularly polarized mode; its polarization direction is decided by the rotation direction of the SWS. 展开更多
关键词 high power microwave magnetically insulated transmission line oscillator asymmetricmode HEM11 mode circularly polarized mode
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Field-induced Néel vector bi-reorientation of a ferrimagnetic insulator in the vicinity of compensation temperature
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作者 Peng Wang Hui Zhao +3 位作者 Zhongzhi Luan Siyu Xia Tao Feng Lifan Zhou 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第2期481-486,共6页
The spin Hall magnetoresistance(SMR)effect in Pt/Gd_(3)Fe_(5)O_(12)(Gd IG)bilayers was systematically investigated.The sign of SMR changes twice with increasing magnetic field in the vicinity of the magnetization comp... The spin Hall magnetoresistance(SMR)effect in Pt/Gd_(3)Fe_(5)O_(12)(Gd IG)bilayers was systematically investigated.The sign of SMR changes twice with increasing magnetic field in the vicinity of the magnetization compensation point(TM)of Gd IG.However,conventional SMR theory predicts the invariant SMR sign in the heterostructure composed of a heavy metal film in contact with a ferromagnetic or antiferromagnetic film.We conclude that this is because of the significant enhancement of the magnetic moment of the Gd sub-lattice and the unchanged moment of the Fe sub-lattice with a relatively large field,meaning that a small net magnetic moment is induced at TM.As a result,the Néel vector aligns with the field after the spin-flop transition,meaning that a bi-reorientation of the Néel vector is produced.Theoretical calculations based on the Néel’s theory and SMR theory also support our conclusions.Our findings indicate that the Néel-vector direction of a ferrimagnet can be tuned across a wide range by a relatively low external field around TM. 展开更多
关键词 spin Hall magnetoresistance FERRIMAGNETS magnetic insulators magnetization switching
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Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface
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作者 Runrun Hao Hai Zhong +7 位作者 Yun Kang Yufei Tian Shishen Yan Guolei Liu Guangbing Han Shuyun Yu Liangmo Mei Shishou Kang 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第3期401-404,共4页
The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in PffYIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic in... The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in PffYIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect (ISHE) in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents (σsc), the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electro-chemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 (Py) than that of Ni is obtained from the nonlocal voltage measurements. 展开更多
关键词 spin transparency spin current magnetic insulator inverse Hall effect
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HEM_(11) mode magnetically insulated transmission line oscillator:Simulation and experiment
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作者 王冬 秦奋 +4 位作者 文杰 陈代兵 金晓 安海狮 张新凯 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第8期211-215,共5页
A novel magnetically insulated transmission line oscillator (MILO) in which a modified HEM11 mode is taken as its main interaction mode (HEM11 mode MILO) is simulated and experimented in this paper. The excitation... A novel magnetically insulated transmission line oscillator (MILO) in which a modified HEM11 mode is taken as its main interaction mode (HEM11 mode MILO) is simulated and experimented in this paper. The excitation of the oscillation mode is made possible by carefully adjusting the arrangement of each resonant cavity in a two-dimensional slow wave structure. The special feature of such a device is that in the slow-wave-structure region, the interaction mode is HEM11 mode which is a TM-like one that could interact with electron beams effectively; and in the coaxial output region, the microwave mode is TE11 mode which has a favourable field density pattern to be directly radiated. Employing an electron beam of about 441 kV and 39.7 kA, the HEM11 mode MILO generates a high power microwave output of about 1.47 GW at 1.45 GHz in particle-in-cell simulation. The power conversion efficiency is about 8.4 % and the generated microwave is in a TEll-like circular polarization mode. In a preliminary experiment investigation, high power microwave is detected from the device with a frequency of 1.46 GHz, an output energy of 43 J 47 J, and a pulse duration of 44 ns-49 ns when the input voltage is 430 kV450 kV, and the diode current is 37 kA-39 kA. 展开更多
关键词 high power microwave magnetically insulated transmission line oscillator asymmetricmode HEM11 mode
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Current loss of magnetically insulated coaxial diode with cathode negative ion
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作者 朱丹妮 张军 +2 位作者 钟辉煌 高景明 白珍 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第2期261-266,共6页
Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode (MICD) is studied through experiment and particle-in-cell (PIC) simulation when the guiding magnetic field is strong e... Current loss without an obvious impedance collapse in the magnetically insulated coaxial diode (MICD) is studied through experiment and particle-in-cell (PIC) simulation when the guiding magnetic field is strong enough. Cathode nega- tive ions are clarified to be the predominant reason for it. Theoretical analysis and simulation both indicate that the velocity of the negative ion reaches up to 1 cm/ns due to the space potential between the anode and cathode gap (A-C gap). Accord- ingly, instead of the reverse current loss and the parasitic current loss, the negative ion loss appears during the whole pulse. The negative ion current loss is determined by its ionization production rate. It increases with diode voltage increasing. The smaller space charge effect caused by the beam thickening and the weaker radial restriction both promote the negative ion production under a lower magnetic field. Therefore, as the magnetic field increases, the current loss gradually decreases until the beam thickening nearly stops. 展开更多
关键词 magnetically insulated coaxial diode (MICD) cathode plasma negative ion current loss
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Simulational Investigation of a High-Efficiency X-Band Magnetically Insulated Line Oscillator
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作者 王晓玉 樊玉伟 《Plasma Science and Technology》 SCIE EI CAS CSCD 2015年第10期893-896,共4页
Abstract The magnetically insulated line oscillator (MILO) is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves (HPM) research. In ... Abstract The magnetically insulated line oscillator (MILO) is a gigawatt-class, coaxial crossed-field microwave tube, which is at present a major hotspot in the field of high-power mi- crowaves (HPM) research. In order to improve the power conversion efficiency and eliminate or at least minimize anode plasma formation in the load region and radio frequency (RF) breakdown in the slow wave structure (SWS) section, an X-band MILO is presented and inyestigated nu- merically with KARAT code. The design idea is briefly presented and the simulation results are given and discussed. In the simulation, HPM is generated with peak power of 3.4 GW, maximum electric field of about 1 MV/cm, and peak power conversion efficiency of 14.0%, when the voltage is 559.1 kV and the current is 43.2 kA. The microwave frequency is pure and falls in the X-band of 9.0 GHz. The theoretical investigation and the simulation results are given to prove that the anode plasma formation and the RF breakdown can be effectively avoided or at least minimized, respectively. 展开更多
关键词 high-power microwaves (HPM) magnetically insulated line oscillator (MILO) anode plasma radio frequency (RF) breakdown
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Effects of the insulated magnetic field and oblique incidence of electrons on the multipactor in MILO
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作者 范杰清 郝建红 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第6期517-523,共7页
The theoretical analysis and actual performance of the single-surface multipactor discharge model in the presence of a magnetic field are conducted through simulations. The effects of the magnitude of the insulated ma... The theoretical analysis and actual performance of the single-surface multipactor discharge model in the presence of a magnetic field are conducted through simulations. The effects of the magnitude of the insulated magnetic field and the oblique incidence of electrons on the multipactor are analysed. The results show that the multipactor susceptibility region shrinks gradually as the magnetic field increases when the electron cyclotron frequency is close to the RF frequency of the electric field. As a result, the evolution of the multipactor discharge will reach saturation earlier and become saturated at a higher level than the case when the magnetic field is absent, but the change of evolution and saturation as the insulated magnetic field increases is not obvious. 展开更多
关键词 MULTIPACTOR susceptibility diagram insulated magnetic field
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A tunable magnetically insulated transmission line oscillator
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作者 樊玉伟 王晓玉 +2 位作者 赫亮 钟辉煌 张建德 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第3期255-258,共4页
A tunable magnetically insulated transmission line oscillator(MILO) is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output po... A tunable magnetically insulated transmission line oscillator(MILO) is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-d B tunable frequency range(the relative output power is above half of the peak output power) is 2.25–0.825 GHz when the outer radius of the slow-wave structure(SWS) vanes ranges from 77 mm to 155 mm, and the 3-d B tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output. 展开更多
关键词 tunable magnetically insulated transmission line oscillator(MILO) particle-in-cell method
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Magnetic Proximity Effect in an Antiferromagnetic Insulator/Topological Insulator Heterostructure with Sharp Interface
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作者 Yuxin Liu Xuefan Niu +3 位作者 Rencong Zhang Qinghua Zhang Jing Teng Yongqing Li 《Chinese Physics Letters》 SCIE CAS CSCD 2021年第5期84-88,共5页
We report an experimental study of electron transport properties of MnSe/(Bi,Sb)_2Te_3 heterostructures,in which MnSe is an antiferromagnetic insulator,and(Bi,Sb)_2Te_3 is a three-dimensional topological insulator(TI)... We report an experimental study of electron transport properties of MnSe/(Bi,Sb)_2Te_3 heterostructures,in which MnSe is an antiferromagnetic insulator,and(Bi,Sb)_2Te_3 is a three-dimensional topological insulator(TI).Strong magnetic proximity effect is manifested in the measurements of the Hall effect and longitudinal resistances.Our analysis shows that the gate voltage can substantially modify the anomalous Hall conductance,which exceeds 0.1 e^(2)/h at temperature T=1.6 K and magnetic field μ_0H=5 T,even though only the top TI surface is in proximity to MnSe.This work suggests that heterostructures based on antiferromagnetic insulators provide a promising platform for investigating a wide range of topological spintronic phenomena. 展开更多
关键词 DIRAC magnetic Proximity Effect in an Antiferromagnetic Insulator/Topological Insulator Heterostructure with Sharp Interface SHARP
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On the half-quantized Hall conductance of massive surface electrons in magnetic topological insulator films
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作者 Rui Chen Shun-Qing Shen 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2024年第6期127-136,共10页
In topological insulators,massive surface states resulting from local symmetry breaking were thought to exhibit a half-quantized Hall conductance,obtained from the low-energy effective model in an infinite Brillouin z... In topological insulators,massive surface states resulting from local symmetry breaking were thought to exhibit a half-quantized Hall conductance,obtained from the low-energy effective model in an infinite Brillouin zone.In a lattice model,the surface band is composed of a combination of surface states and bulk states.The massive surface states alone may not be enough to support an exact one-half quantized surface Hall conductance in a finite Brillouin zone and the whole surface band always gives an integer quantized Hall conductance as enforced by the TKNN theorem.To explore this,we investigate the band structures of a lattice model describing the magnetic topological insulator film that supports the axion insulator,Chern insulator,and semi-magnetic topological insulator phases.We reveal that the gapped and gapless surface bands in the three phases are characterized by an integer-quantized Hall conductance and a half-quantized Hall conductance,respectively.We propose an effective model to describe the three phases and show that the low-energy dispersion of the surface bands inherits from the surface Dirac fermions.The gapped surface band manifests a nearly half-quantized Hall conductance at low energy near the center of Brillouin zone,but is compensated by another nearly half-quantized Hall conductance at high energy near the boundary of Brillouin zone because a single band can only have an integer-quantized Hall conductance.The gapless band hosts a zero Hall conductance at low energy but is compensated by another half-quantized Hall conductance at high energy,and thus the half-quantized Hall conductance can only originate from the gapless band.Moreover,we calculate the layer-resolved Hall conductance of the system.The conclusion suggests that the individual gapped surface band alone does not support the half-quantized surface Hall effect in a lattice model. 展开更多
关键词 magnetic topological insulator Dirac equation half-quantized Hall conductance
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Magnetic and electrical transport study of the intrinsic magnetic topological insulator MnBi_(2)Te_(4)with Ge doping
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作者 Qingwang Bai Mingxiang Xu 《Frontiers of physics》 SCIE CSCD 2024年第3期51-59,共9页
As an intrinsic magnetic topological insulator with magnetic order and non-trivial topological structure,MnBi_(2)Te_(4)is an ideal material for studying exotic topological states such as quantum anomalous Hall effect ... As an intrinsic magnetic topological insulator with magnetic order and non-trivial topological structure,MnBi_(2)Te_(4)is an ideal material for studying exotic topological states such as quantum anomalous Hall effect and topological axion insulating states.Here,we carry out magnetic and electrical transport measurements on(Mn1–xGex)Bi_(2)Te_(4)(x=0,0.15,0.30,0.45,0.60,and 0.75)single crystals.It is found that with increasing x,the dilution of magnetic moments gradually weakens the antiferromagnetic exchange interaction.Moreover,Ge doping reduces the critical field of ferromagnetic ordering,which may provide a possible way to implement the quantum anomalous Hall effect at lower magnetic field.Electrical transport measurements suggest that electrons are the dominant charge carriers,and the carrier density increases with the Ge doping ratio.Additionally,the Kondo effect is observed in the samples with x=0.45,0.60,and 0.75.Our results suggest that doping germanium is a viable way to tune the magnetic and electrical transport properties of MnBi_(2)Te_(4),opening up the possibility of future applications in magnetic topological insulators. 展开更多
关键词 MnBi_(2)Te_(4) intrinsic magnetic topological insulator transition points Kondo effect
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Experimental study of current loss of a single-hole post-hole convolute on the QG I generator 被引量:1
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作者 Hanyu WU Zhengzhong ZENG +4 位作者 Mengtong QIU Peitian CONG Jinhai ZHANG Xinjun ZHANG Ning GUO 《Plasma Science and Technology》 SCIE EI CAS CSCD 2020年第1期104-110,共7页
The post-hole convolute(PHC),which is used to transport and combine the pulse power flux,is a key component in huge pulsed power generators.Current loss at the PHC is a challenging problem for researchers.To explore a... The post-hole convolute(PHC),which is used to transport and combine the pulse power flux,is a key component in huge pulsed power generators.Current loss at the PHC is a challenging problem for researchers.To explore a method of reducing the current loss,a single-hole PHC was designed for experiments on the current loss on the Qiang Guang I generator.The experimental results showed that the current loss at the single-hole PHC is related to the distance/between the vicinity of the cathode hole and the surface of the downstream side of the post.Meanwhile,a single-hole PHC with a blob cathode hole transmitted current more effectively than the PHC with a circle cathode hole.The relative current loss at the single-hole PHC with the cathode coaled w ith gold foil was about 30%-50% of that with the cathode coated with nickel and titanium foil.The gap closing speed was also obtained from the current waveforms in the experiments.The speed was 5.74-14.52 cmμs 1 which was different from the classical plasma expansion velocity of 3 cmμs 1. 展开更多
关键词 plasma post-hole convolute magnetic insulation current loss
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