In magnetic topological materials,the interplay between magnetism and nontrivial topology gives rise to exotic quantum transport phenomena,including the anomalous Hall effect and anomalous Nernst effect.Here,we report...In magnetic topological materials,the interplay between magnetism and nontrivial topology gives rise to exotic quantum transport phenomena,including the anomalous Hall effect and anomalous Nernst effect.Here,we report the observation of intrinsic topological Hall and topological Nernst effects below the Néel temperature(T_(N)=25 K)in the antiferromagnetic(AFM)topological insulator Mn Bi_(2)Te_(4).The maximum of topological Hall resistivity reaches approximately 9μΩ·cm at 2 K,while the topological Nernst signal attains a peak value of 0.1μV/K near 10 K.These anomalous transport behaviors originate from the net Berry curvature induced by the non-collinear spin structure in the canted AFM state.Our results suggest a close connection between the topological thermoelectric effect and non-collinear AFM order in AFM topological insulators.展开更多
Free electron radiation,particularly Smith-Purcell radiation,provides a versatile platform for exploring lightmatter interactions and generating light sources.A fundamental characteristic of Smith-Purcell radiation is...Free electron radiation,particularly Smith-Purcell radiation,provides a versatile platform for exploring lightmatter interactions and generating light sources.A fundamental characteristic of Smith-Purcell radiation is the monotonic decrease in radiation frequency as the observation angle increases relative to the direction of the free electrons’motion,akin to the Doppler effect.Here,we demonstrate that this fundamental characteristic can be altered in Smith-Purcell radiation generated by photonic crystals with left-handed properties.Specifically,we have achieved,to our knowledge,a novel phenomenon that the lower-frequency components propagate forward,while the higher-frequency components propagate backward,which we define as reverse Smith-Purcell radiation.Additionally,this reverse Smith-Purcell radiation can confine the radiation to a narrow angular range,which provides a way to obtain broadband light sources in a specific observation angle.Furthermore,by precisely adjusting the grating geometry and the kinetic energy of the free electrons,we can control both the radiation direction and the output frequencies.Our results provide a promising platform to study unexplored light-matter interactions and open avenues to obtain tunable,broadband light sources.展开更多
基金supported in part by the Natural Science Foundation of China(Grant No.U1932155)the Hangzhou Joint Fund of the Zhejiang Provincial Natural Science Foundation of China(Grant No.LHZSZ24A040001)+4 种基金the National Key R&D Program of China(Grant No.2022YFA1602602)the National Key R&D Program of China(Grant Nos.2022YFA1403800 and 20-23YFA1406500)the China Postdoctoral Science Foundation(Grant No.2023-M730011)the National Natural Science Foundation of China(Grant No.12274459)supported by the HZNU Scientific Research and Innovation Team Project(No.TD2025013)。
文摘In magnetic topological materials,the interplay between magnetism and nontrivial topology gives rise to exotic quantum transport phenomena,including the anomalous Hall effect and anomalous Nernst effect.Here,we report the observation of intrinsic topological Hall and topological Nernst effects below the Néel temperature(T_(N)=25 K)in the antiferromagnetic(AFM)topological insulator Mn Bi_(2)Te_(4).The maximum of topological Hall resistivity reaches approximately 9μΩ·cm at 2 K,while the topological Nernst signal attains a peak value of 0.1μV/K near 10 K.These anomalous transport behaviors originate from the net Berry curvature induced by the non-collinear spin structure in the canted AFM state.Our results suggest a close connection between the topological thermoelectric effect and non-collinear AFM order in AFM topological insulators.
基金National Natural Science Foundation of China(61988102,62401113)Natural Science Foundation of Sichuan Province(25QNJJ2315)Fund of Key Laboratory of THz Technology,Ministry of Education。
文摘Free electron radiation,particularly Smith-Purcell radiation,provides a versatile platform for exploring lightmatter interactions and generating light sources.A fundamental characteristic of Smith-Purcell radiation is the monotonic decrease in radiation frequency as the observation angle increases relative to the direction of the free electrons’motion,akin to the Doppler effect.Here,we demonstrate that this fundamental characteristic can be altered in Smith-Purcell radiation generated by photonic crystals with left-handed properties.Specifically,we have achieved,to our knowledge,a novel phenomenon that the lower-frequency components propagate forward,while the higher-frequency components propagate backward,which we define as reverse Smith-Purcell radiation.Additionally,this reverse Smith-Purcell radiation can confine the radiation to a narrow angular range,which provides a way to obtain broadband light sources in a specific observation angle.Furthermore,by precisely adjusting the grating geometry and the kinetic energy of the free electrons,we can control both the radiation direction and the output frequencies.Our results provide a promising platform to study unexplored light-matter interactions and open avenues to obtain tunable,broadband light sources.
