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
Since the discovery of the Nernst effect in 19th century,it has been an important transverse thermoelectric charge transport phenomenon in solid states.Conjugated polymers have recently attracted great attention as pr...Since the discovery of the Nernst effect in 19th century,it has been an important transverse thermoelectric charge transport phenomenon in solid states.Conjugated polymers have recently attracted great attention as promising optoelectronic materials.However,the Nernst effect is yet to be explored for conducting polymers.Here,we report the first theoretical investigations of the Nernst effect in doped conducting polymers by first-principles calculations under the frame work of Fermi-liquid theory.Specifically,the Nernst coefficients of PBTTT are found to be ranging from 0.0029 to 0.039μV K^(-1)T^(-1).They are monotonically decreased with the doping level due to both much enhanced Fermi energy and the decreased charge mobility at high doping level.Our theoretical findings not only enhance our fundamental understanding of the doping mechanism that controls the charge transport properties of conducting polymers,but more importantly,they also offer initial predictions of the transverse thermoelectric conversion capability of conducting polymers.These predictions are crucial for the development of future flexible thermoelectric applications based on the Nernst effect.展开更多
Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene syste...Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model.It is found that the total valley Nernst coefficient(VNC)is three orders of magnitude larger than that in monolayer group-Ⅵdichalcogenides.The total VNC increases with the increase of layer numbers.It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy.We identify that the central peak is always negative stemming from the flat band.Two shoulder peaks are positively induced by the conduction and valence bands,respectively.These predicted features can be tested experimentally.The present work would shed more light on valley caloritronics.展开更多
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
The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization.In this work,we propose a novel dynamical chiral Nernst effec...The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization.In this work,we propose a novel dynamical chiral Nernst effect that can appear in two-dimensional van der Waals materials with chiral structural symmetry in the absence of any magnetic degree of freedom.This unconventional effect is triggered by time variation of an out-of-plane electric field,and has an intrinsic quantum geometric origin linked to not only the intralayer center-of-mass motion but also the interlayer coherence of electronic states.We demonstrate the effect in twisted homobilayer and homotrilayer transition metal dichalcogenides,where the strong twisted interlayer coupling leads to sizable intrinsic Nernst conductivities well within the experimental capacity.This work suggests a new route for electric control of thermoelectric conversion.展开更多
Thermoelectric coolers utilizing the Peltier effect have dominated the field of solid-state cooling but their efficiency is hindered by material limitations.Alternative routes based on the Thomson and Nernst effects o...Thermoelectric coolers utilizing the Peltier effect have dominated the field of solid-state cooling but their efficiency is hindered by material limitations.Alternative routes based on the Thomson and Nernst effects offer new possibilities.Here,we present a comprehensive investigation of the thermoelectric properties of 1T-TiSe_(2),focusing on these effects around the charge density wave transition(≈200 K).The abrupt Fermi surface reconstruction associated with this transition leads to an exceptional peak in the Thomson coefficient of 450μVK^(-1) at 184 K,surpassing the Seebeck coefficient.Furthermore,1T-TiSe_(2) exhibits a remarkably broad temperature range(170-400 K)with a Thomson coefficient exceeding 190μV K^(-1),a characteristic highly desirable for the development of practical Thomson coolers with extended operational ranges.Additionally,the Nernst coefficient exhibits an unusual temperature dependence,increasing with temperature in the normal phase,which we attribute to bipolar conduction effects.The combination of solid-solid pure electronic phase transition to a semimetallic phase with bipolar transport is identified as responsible for the unusual Nernst trend and the unusually large Thomson coefficient over a broad temperature range.展开更多
A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the batter...A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the battery are considered. A simple algorithm, with variable time step-length <span style="font-family:Verdana;">Δ</span><i><span style="font-family:Verdana;">t</span></i><span style="font-family:Verdana;">, is presented, for proposed model. The model is first applied to Daniel cell, in order to clar</span><span style="font-family:Verdana;">ify</span><span style="font-family:""><span style="font-family:Verdana;"> concepts and principles of battery operation. It is found that initial pinching, in time-history curve of voltage </span><i><span style="font-family:Verdana;">E-t</span></i><span style="font-family:Verdana;">, is due to initial under-concentration of product ion. Then, model is applied </span></span><span style="font-family:Verdana;">to</span><span> a lead-acid battery. In absence of an ion product, and in order to construct nominator of Nernst ratio, such an ion, with coefficient tending to zero, is assumed, thus yielding unity in nominator. Time-history curves of voltage, for various values of internal resistance, are compared with corresponding published experimental curves. Temperature effect on voltage-time curve is examined. Proposed model can be extended to other types of batteries, which can be considered as having aqueous electrolytes, too.</span>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financial support from the National Natural Science Foundation of China(Nos.22125504,22175186,62205347,22305253,62075224,22021002 and 21805285)the Natural Science Foundation of Beijing(No.Z220025)the K.C.Wong Education Foundation(No.GJTD-2020-02)。
文摘Since the discovery of the Nernst effect in 19th century,it has been an important transverse thermoelectric charge transport phenomenon in solid states.Conjugated polymers have recently attracted great attention as promising optoelectronic materials.However,the Nernst effect is yet to be explored for conducting polymers.Here,we report the first theoretical investigations of the Nernst effect in doped conducting polymers by first-principles calculations under the frame work of Fermi-liquid theory.Specifically,the Nernst coefficients of PBTTT are found to be ranging from 0.0029 to 0.039μV K^(-1)T^(-1).They are monotonically decreased with the doping level due to both much enhanced Fermi energy and the decreased charge mobility at high doping level.Our theoretical findings not only enhance our fundamental understanding of the doping mechanism that controls the charge transport properties of conducting polymers,but more importantly,they also offer initial predictions of the transverse thermoelectric conversion capability of conducting polymers.These predictions are crucial for the development of future flexible thermoelectric applications based on the Nernst effect.
基金Project supported in part by the National Key R&D Program of China(Grant No.2018YFA0305800)the National Natural Science Foundation of China(Grant Nos.11974348 and 11834014)+2 种基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB28000000 and XDB33000000)supported in part by the Training Program of Major Research plan of the National Natural Science Foundation of China(Grant No.92165105)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-057)。
文摘Valley Nernst effect is a newly proposed and experimentally confirmed effect,which could be used to design novel thermoelectric devices.We study the valley Nernst effect in(M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model.It is found that the total valley Nernst coefficient(VNC)is three orders of magnitude larger than that in monolayer group-Ⅵdichalcogenides.The total VNC increases with the increase of layer numbers.It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy.We identify that the central peak is always negative stemming from the flat band.Two shoulder peaks are positively induced by the conduction and valence bands,respectively.These predicted features can be tested experimentally.The present work would shed more light on valley caloritronics.
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 R&D Program of China(Grant No.2020YFA0309600)the Research Grant Council of Hong Kong(AoE/P-701/20,HKU SRFS2122-7S05,A-HKU705/21)New Cornerstone Science Foundation.C.X.also acknowledges support by the UM Start-up Grant(SRG2023-00033-IAPME).
文摘The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization.In this work,we propose a novel dynamical chiral Nernst effect that can appear in two-dimensional van der Waals materials with chiral structural symmetry in the absence of any magnetic degree of freedom.This unconventional effect is triggered by time variation of an out-of-plane electric field,and has an intrinsic quantum geometric origin linked to not only the intralayer center-of-mass motion but also the interlayer coherence of electronic states.We demonstrate the effect in twisted homobilayer and homotrilayer transition metal dichalcogenides,where the strong twisted interlayer coupling leads to sizable intrinsic Nernst conductivities well within the experimental capacity.This work suggests a new route for electric control of thermoelectric conversion.
基金S.A.and M.Z.acknowledge support by NSF,grant number 2230352S.S.D.acknowledges support from the UVA Research Innovation AwardK.S.D.and D.L.work on TMDs has been supported by National Science Foundation Grant No.221949.
文摘Thermoelectric coolers utilizing the Peltier effect have dominated the field of solid-state cooling but their efficiency is hindered by material limitations.Alternative routes based on the Thomson and Nernst effects offer new possibilities.Here,we present a comprehensive investigation of the thermoelectric properties of 1T-TiSe_(2),focusing on these effects around the charge density wave transition(≈200 K).The abrupt Fermi surface reconstruction associated with this transition leads to an exceptional peak in the Thomson coefficient of 450μVK^(-1) at 184 K,surpassing the Seebeck coefficient.Furthermore,1T-TiSe_(2) exhibits a remarkably broad temperature range(170-400 K)with a Thomson coefficient exceeding 190μV K^(-1),a characteristic highly desirable for the development of practical Thomson coolers with extended operational ranges.Additionally,the Nernst coefficient exhibits an unusual temperature dependence,increasing with temperature in the normal phase,which we attribute to bipolar conduction effects.The combination of solid-solid pure electronic phase transition to a semimetallic phase with bipolar transport is identified as responsible for the unusual Nernst trend and the unusually large Thomson coefficient over a broad temperature range.
文摘A simple rational model is proposed for discharge of batteries with aqueous electrolytes, based on Nernst equation. Details of electrode kinetics are not taken into account. Only a few overall parameters of the battery are considered. A simple algorithm, with variable time step-length <span style="font-family:Verdana;">Δ</span><i><span style="font-family:Verdana;">t</span></i><span style="font-family:Verdana;">, is presented, for proposed model. The model is first applied to Daniel cell, in order to clar</span><span style="font-family:Verdana;">ify</span><span style="font-family:""><span style="font-family:Verdana;"> concepts and principles of battery operation. It is found that initial pinching, in time-history curve of voltage </span><i><span style="font-family:Verdana;">E-t</span></i><span style="font-family:Verdana;">, is due to initial under-concentration of product ion. Then, model is applied </span></span><span style="font-family:Verdana;">to</span><span> a lead-acid battery. In absence of an ion product, and in order to construct nominator of Nernst ratio, such an ion, with coefficient tending to zero, is assumed, thus yielding unity in nominator. Time-history curves of voltage, for various values of internal resistance, are compared with corresponding published experimental curves. Temperature effect on voltage-time curve is examined. Proposed model can be extended to other types of batteries, which can be considered as having aqueous electrolytes, too.</span>
