We propose the realization of Majorana fermions （MFs） on the edges of a two-dimensional topological insulator in the proximity with s-wave superconductors and in the presence of transverse exchange field h. It is sh...We propose the realization of Majorana fermions （MFs） on the edges of a two-dimensional topological insulator in the proximity with s-wave superconductors and in the presence of transverse exchange field h. It is shown that there appear a pair of MFs localized at two junctions and that a reverse in the direction of h can lead to permutation of two MFs. With decreasing h, the MF states can either be fused or form one Dirac fermion on the π-junctions, exhibiting a topological phase transition. This characteristic can be used to detect physical states of MFs when they are transformed into Dirac fermions MFs is also given. localized on the π-junction. A condition of decoupling two展开更多
Using the method of Picus and Beer invariants, general expressions are obtained for the total intensity I and the degree of circular polarization Рcirc.of the luminescence of GaAs-type semiconductors with the partici...Using the method of Picus and Beer invariants, general expressions are obtained for the total intensity I and the degree of circular polarization Рcirc.of the luminescence of GaAs-type semiconductors with the participation of shallow acceptor levels in a longitudinal magnetic field H. Special cases are analyzed depending on the value and direction of the magnetic field strength, as well as on the constants of the g-factor of the acceptor g1,g2and the conduction band electron ge. In the case of a strong magnetic field H// [100], [111], [110], a numerical calculation of the angular dependence of the quantities I and Рcirc.was performed for some critical values of g2/g1, at which Рcirc.exhibits a sharp anisotropy in the range from −100% to +100%, and the intensity of the crystal radiation along the magnetic field tends to a minimum value.展开更多
By utilizing a natural mercury lamp, the transverse Zeeman background correction method, which is used for trace mercury measurement in air, is studied. In this paper, a natural mercury lamp is used as a light source,...By utilizing a natural mercury lamp, the transverse Zeeman background correction method, which is used for trace mercury measurement in air, is studied. In this paper, a natural mercury lamp is used as a light source, and is placed in a 1.78-T magnetic field. The lamp emits two linearly polarized light beams σ± and π of 253.65-nm resonance line, which are used as bias light and absorbing light, respectively. A polarization modulation system is used to allow σ± and π light beams to pass through alternately with a certain frequency. A multipath optical cell with 12-m optical path is used to increase optical distance. Based on the system described above, the influence caused by UV absorbing gases, such as NO2, SO2, acetone, benzene, and O3, is analyzed. The results show that it may reduce the detection limit when the concentrations of these gases exceed 83.4 ppm, 20.3 ppm, 142.3 ppm, 0.85 ppm, and 0.55 ppm, respectively. The detection limit of the system is calculated and can achieve up to 1.44 ng/m3 in 10 minutes. Measurements on mercury sample gas and air are carded out, and the measured data are compared with the data of RA-915 mercury analyzer （Russia）. The result shows that the correlation coefficient reaches up to 0.967. The experimental results indicate that the transverse Zeeman background correction method can be used to quantify trace mercury in air with high-precision.展开更多
Higher-order topological insulators(HOTIs),with topological corner or hinge states,have emerged as a thriving topic in the field of topological physics.However,few connections have been found for HOTIs with well-explo...Higher-order topological insulators(HOTIs),with topological corner or hinge states,have emerged as a thriving topic in the field of topological physics.However,few connections have been found for HOTIs with well-explored first-order topological insulators.Recently a proposal asserted that a significant bridge can be established between the HOTIs and Z2 topological insulators.When subjected to an inplane Zeeman field,corner states,the signature of the HOTIs,can be induced in a Z2 topological insulator.Such Zeeman fields can be produced,for example,by the ferromagnetic proximity effect or magnetic atom doping,which drastically increases the experimental complexity.Here,we show that a phononic crystal,designed as a bilayer of coupled acoustic cavities,exactly hosts the Kane-Mele model with built-in in-plane Zeeman fields.The helical edge states along the zigzag edges are gapped,and the corner states,localized spatially at the corners of the samples,appear in the gap.This verifies the Zeeman field induced higher-order topology.We further demonstrate the intriguing contrast properties of the corner states at the outer and inner corners in a hexagonal ring-shaped sample.展开更多
目的建立动态三磁场塞曼背景校正石墨炉原子吸收法测定工作场所空气中铅及其化合物的分析方法。方法用微孔滤膜采集空气样品,使用高氯酸—硝酸(1∶9,V∶V)消解,以1%硝酸定容至25 m L,在283.3 nm波长下,使用动态三磁场塞曼背景校正模式...目的建立动态三磁场塞曼背景校正石墨炉原子吸收法测定工作场所空气中铅及其化合物的分析方法。方法用微孔滤膜采集空气样品,使用高氯酸—硝酸(1∶9,V∶V)消解,以1%硝酸定容至25 m L,在283.3 nm波长下,使用动态三磁场塞曼背景校正模式进行测定。结果使用动态三磁场模式,同时得到2-磁场和3-磁场模式下的吸光值及校正曲线,在0~800μg/L质量浓度范围内有较好的线性关系,其中0~100μg/L浓度范围采用二磁场模式校正曲线,曲线方程为A=2.76×10^(-3)C+2.08×10^(-2),r=0.9975,特征浓度1.58μg/L;100μg/L^800μg/L浓度范围采用三磁场模式校正曲线,曲线方程A=(4.05×10^(-3)+9.67×10^(-4)C)/(1+6.50×10^(-4)C),r=0.9970,特征浓度4.51μg/L,方法最低检出浓度为2.6μg/L,加标回收率为95.1%~104.8%,RSD为2.4%~4.5%。结论本法操作简单,兼具两种磁场模式的优点,有效扩展了线性范围,准确灵敏,适用于不同浓度级别空气中铅及其化合物的同时测定。展开更多
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No BK20140588the Research Grant Council of Hongkong under Grant No HKU7058/11P+1 种基金the CRF of the Research Grant Council of Hongkong under Grant No HKU-8/11Gthe National Basic Research Program of China under Grant No 2011CB922103
文摘We propose the realization of Majorana fermions （MFs） on the edges of a two-dimensional topological insulator in the proximity with s-wave superconductors and in the presence of transverse exchange field h. It is shown that there appear a pair of MFs localized at two junctions and that a reverse in the direction of h can lead to permutation of two MFs. With decreasing h, the MF states can either be fused or form one Dirac fermion on the π-junctions, exhibiting a topological phase transition. This characteristic can be used to detect physical states of MFs when they are transformed into Dirac fermions MFs is also given. localized on the π-junction. A condition of decoupling two
文摘Using the method of Picus and Beer invariants, general expressions are obtained for the total intensity I and the degree of circular polarization Рcirc.of the luminescence of GaAs-type semiconductors with the participation of shallow acceptor levels in a longitudinal magnetic field H. Special cases are analyzed depending on the value and direction of the magnetic field strength, as well as on the constants of the g-factor of the acceptor g1,g2and the conduction band electron ge. In the case of a strong magnetic field H// [100], [111], [110], a numerical calculation of the angular dependence of the quantities I and Рcirc.was performed for some critical values of g2/g1, at which Рcirc.exhibits a sharp anisotropy in the range from −100% to +100%, and the intensity of the crystal radiation along the magnetic field tends to a minimum value.
基金Project supported by the National Natural Science Foundation of China(Grant No.41275037)the Science-Technology Foundation for Young Scientist of Anhui Province,China(Grant No.1308085JGD03)the Anhui Provincial Natural Science Foundation,China(Grant No.1308085QF124)
文摘By utilizing a natural mercury lamp, the transverse Zeeman background correction method, which is used for trace mercury measurement in air, is studied. In this paper, a natural mercury lamp is used as a light source, and is placed in a 1.78-T magnetic field. The lamp emits two linearly polarized light beams σ± and π of 253.65-nm resonance line, which are used as bias light and absorbing light, respectively. A polarization modulation system is used to allow σ± and π light beams to pass through alternately with a certain frequency. A multipath optical cell with 12-m optical path is used to increase optical distance. Based on the system described above, the influence caused by UV absorbing gases, such as NO2, SO2, acetone, benzene, and O3, is analyzed. The results show that it may reduce the detection limit when the concentrations of these gases exceed 83.4 ppm, 20.3 ppm, 142.3 ppm, 0.85 ppm, and 0.55 ppm, respectively. The detection limit of the system is calculated and can achieve up to 1.44 ng/m3 in 10 minutes. Measurements on mercury sample gas and air are carded out, and the measured data are compared with the data of RA-915 mercury analyzer （Russia）. The result shows that the correlation coefficient reaches up to 0.967. The experimental results indicate that the transverse Zeeman background correction method can be used to quantify trace mercury in air with high-precision.
基金supported by the National Natural Science Foundation of China(11890701,11974120,11974005,12074128,12074232,12125406,and 12174455)the National Key R&D Program of China(2018YFA0305800)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(2019B151502012,2021B1515020086,and 2021A1515010347)the Science and Technology Projects in Guangzhou(202102020960)。
文摘Higher-order topological insulators(HOTIs),with topological corner or hinge states,have emerged as a thriving topic in the field of topological physics.However,few connections have been found for HOTIs with well-explored first-order topological insulators.Recently a proposal asserted that a significant bridge can be established between the HOTIs and Z2 topological insulators.When subjected to an inplane Zeeman field,corner states,the signature of the HOTIs,can be induced in a Z2 topological insulator.Such Zeeman fields can be produced,for example,by the ferromagnetic proximity effect or magnetic atom doping,which drastically increases the experimental complexity.Here,we show that a phononic crystal,designed as a bilayer of coupled acoustic cavities,exactly hosts the Kane-Mele model with built-in in-plane Zeeman fields.The helical edge states along the zigzag edges are gapped,and the corner states,localized spatially at the corners of the samples,appear in the gap.This verifies the Zeeman field induced higher-order topology.We further demonstrate the intriguing contrast properties of the corner states at the outer and inner corners in a hexagonal ring-shaped sample.
文摘目的建立动态三磁场塞曼背景校正石墨炉原子吸收法测定工作场所空气中铅及其化合物的分析方法。方法用微孔滤膜采集空气样品,使用高氯酸—硝酸(1∶9,V∶V)消解,以1%硝酸定容至25 m L,在283.3 nm波长下,使用动态三磁场塞曼背景校正模式进行测定。结果使用动态三磁场模式,同时得到2-磁场和3-磁场模式下的吸光值及校正曲线,在0~800μg/L质量浓度范围内有较好的线性关系,其中0~100μg/L浓度范围采用二磁场模式校正曲线,曲线方程为A=2.76×10^(-3)C+2.08×10^(-2),r=0.9975,特征浓度1.58μg/L;100μg/L^800μg/L浓度范围采用三磁场模式校正曲线,曲线方程A=(4.05×10^(-3)+9.67×10^(-4)C)/(1+6.50×10^(-4)C),r=0.9970,特征浓度4.51μg/L,方法最低检出浓度为2.6μg/L,加标回收率为95.1%~104.8%,RSD为2.4%~4.5%。结论本法操作简单,兼具两种磁场模式的优点,有效扩展了线性范围,准确灵敏,适用于不同浓度级别空气中铅及其化合物的同时测定。
