Berry curvature describes the intrinsic geometric property of electronic band structure,crucial for governing emergent transport phenomena.As a typical Berry-curvature-related property,the anomalous Nernst effect prob...Berry curvature describes the intrinsic geometric property of electronic band structure,crucial for governing emergent transport phenomena.As a typical Berry-curvature-related property,the anomalous Nernst effect probes local Berry curvature near the Fermi surface,whereas the anomalous Hall effect integrates contributions across all occupied states.Thus,the anomalous Nernst effect is a superior probe for detecting subtle evolution of Berry curvature near the Fermi level;however,their relation remains elusive.Here,we demonstrate giant anomalous Nernst angles induced by Berry curvature in layered itinerant ferromagnets Fe_(3)GaTe_(2)and Fe_(5)GeTe_(2).Their maximum values(≈0.33 for Fe_(3)GaTe_(2)and≈0.41 for Fe_(5)GeTe_(2))are one order of magnitude larger than those of traditional ferromagnets(θ_(AN)^(max)<0.02).Scaling analysis of anomalous Hall effect in these two systems further suggests these giant angles originate from intrinsic Berry curvature.These findings indicate Berrycurvature-dominated regimes,and establish these materials for high-performance spin-caloritronic devices.展开更多
Topological magnets have shown great potential for transverse thermoelectric(TE)conversion with structural advantages,utilizing the anomalous Nernst effect.To facilitate such applications,the development of exceptiona...Topological magnets have shown great potential for transverse thermoelectric(TE)conversion with structural advantages,utilizing the anomalous Nernst effect.To facilitate such applications,the development of exceptional topological magnet-based Nernst devices is a crucial step that requires both high-performance topological magnets and the design of low-resistance interfaces in the devices.Here,we report that the anomalous Nernst effect in topological magnets can be ubiquitously enhanced by synergistically tuning the entropy-density-weighted Berry curvature and the Fermi surface,as evidenced by a giant anomalous Nernst power factor of 47.8μW m^(-1) K^(-2) at room temperature in electron-doped Co2MnGa.In addition,we achieved an ultralow interfacial resistivity in the Nernst device by designing reactive wetting interfacial layers,enabling an ultrahigh power output of 69.7μW at a temperature difference of 16.1 K,the highest value yet reported to date.We have also experimentally corroborated the structural advantages of transverse TE technology by developing Nernst devices with different length-to-thickness ratios.Our work demonstrates a paradigm for designing exceptional topological magnetbased Nernst generators for transverse TE conversion.展开更多
The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomen...The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomena,such as unconventional superconductivity,chiral charge density wave and electronic nematicity.These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV3Sb5,both in electrical and thermal channels,which are prominent probes to uncover the underlying mechanisms.In this brief review,we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of A V3Sb5,including giant anomalous Hall,anomalous Nernst,ambipolar Nernst and anomalous thermal Hall effects.Connections of these anomalous transport properties to time-reversal symmetry breaking,topological and multiband fermiology,as well as electronic nematicity,are also discussed.Finally,a perspective together with challenges of this rapid growing field are given.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1408104,2021YFA1202901,and 2022YFA1204001)the National Natural Science Foundation of China(Grant Nos.92365203,U24A6002,52302180,and U21A2086)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20243011)the Hebei Natural Science Foundation No.E2023203002).
文摘Berry curvature describes the intrinsic geometric property of electronic band structure,crucial for governing emergent transport phenomena.As a typical Berry-curvature-related property,the anomalous Nernst effect probes local Berry curvature near the Fermi surface,whereas the anomalous Hall effect integrates contributions across all occupied states.Thus,the anomalous Nernst effect is a superior probe for detecting subtle evolution of Berry curvature near the Fermi level;however,their relation remains elusive.Here,we demonstrate giant anomalous Nernst angles induced by Berry curvature in layered itinerant ferromagnets Fe_(3)GaTe_(2)and Fe_(5)GeTe_(2).Their maximum values(≈0.33 for Fe_(3)GaTe_(2)and≈0.41 for Fe_(5)GeTe_(2))are one order of magnitude larger than those of traditional ferromagnets(θ_(AN)^(max)<0.02).Scaling analysis of anomalous Hall effect in these two systems further suggests these giant angles originate from intrinsic Berry curvature.These findings indicate Berrycurvature-dominated regimes,and establish these materials for high-performance spin-caloritronic devices.
基金supported by the National Key Research and Development Program of China(no.2024YFA1409202)the National Natural Science Foundation of China(nos.52471239,U23A20553,92163203,52271016,and 52188101)+1 种基金the Fundamental Research Funds for the Central Universities(226-2024-00075)the Natural Science Foundation of Liaoning Province(no.XLYC2203080).
文摘Topological magnets have shown great potential for transverse thermoelectric(TE)conversion with structural advantages,utilizing the anomalous Nernst effect.To facilitate such applications,the development of exceptional topological magnet-based Nernst devices is a crucial step that requires both high-performance topological magnets and the design of low-resistance interfaces in the devices.Here,we report that the anomalous Nernst effect in topological magnets can be ubiquitously enhanced by synergistically tuning the entropy-density-weighted Berry curvature and the Fermi surface,as evidenced by a giant anomalous Nernst power factor of 47.8μW m^(-1) K^(-2) at room temperature in electron-doped Co2MnGa.In addition,we achieved an ultralow interfacial resistivity in the Nernst device by designing reactive wetting interfacial layers,enabling an ultrahigh power output of 69.7μW at a temperature difference of 16.1 K,the highest value yet reported to date.We have also experimentally corroborated the structural advantages of transverse TE technology by developing Nernst devices with different length-to-thickness ratios.Our work demonstrates a paradigm for designing exceptional topological magnetbased Nernst generators for transverse TE conversion.
基金support by National Natural Science Foundation of China (Grant No. 11904040)Chongqing Research Program of Basic Research and Frontier Technology,China (Grant No. cstc2020jcyj-msxm X0263)Chinesisch-Deutsche Mobilit?tsprogamm of Chinesisch-Deutsche Zentrum für Wissenschaftsf?rderung (Grant No. M-0496)。
文摘The interplay between lattice geometry,band topology and electronic correlations in the newly discovered kagome compounds AV3Sb5(A=K,Rb,Cs) makes this family a novel playground to investigate emergent quantum phenomena,such as unconventional superconductivity,chiral charge density wave and electronic nematicity.These exotic quantum phases naturally leave nontrivial fingerprints in transport properties of AV3Sb5,both in electrical and thermal channels,which are prominent probes to uncover the underlying mechanisms.In this brief review,we highlight the unusual electrical and thermal transport properties observed in the unconventional charge ordered state of A V3Sb5,including giant anomalous Hall,anomalous Nernst,ambipolar Nernst and anomalous thermal Hall effects.Connections of these anomalous transport properties to time-reversal symmetry breaking,topological and multiband fermiology,as well as electronic nematicity,are also discussed.Finally,a perspective together with challenges of this rapid growing field are given.
