Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad7547
Morteza Salehi
We theoretically show that an interface formed by a three-dimensional Dirac/magnetic Weyl semimetal deflects the propagation direction of hitting Weyl fermions according to their Chirality in opposite directions. This effect leads to a Chirality current that flows parallel to the interface. There is an imbalance between the Chirality of Weyl fermions in this current whereas it does not carry any charge. Also, this phenomenon creates an indirect gap in the charge conductance that pass through the circuit. Unlike real spin, Chirality remains a good quantum number in systems characterized by very strong spin-momentum coupling. We derive a continuity equation for the Chirality density wave to elucidate how magnetization alters its dynamics and relates to the transverse Chirality current. Furthermore, we demonstrate a torque, that we called it Chirality transfer torque, imposes on the junction that its value relates to the transverse Chirality current.
我们从理论上证明，由三维狄拉克/磁性韦尔半金属形成的界面会使撞击韦尔费米子的传播方向根据其奇异性向相反方向偏转。这种效应导致了平行于界面的手性电流。在这一电流中，Weyl 费米子的手性之间存在不平衡，而它并不携带任何电荷。此外，这种现象还会在通过电路的电荷传导中产生间接间隙。与真实自旋不同，手性在自旋-动量耦合非常强的系统中仍然是一个很好的量子数。我们推导出了手性密度波的连续性方程，以阐明磁化如何改变其动态以及与横向手性电流的关系。此外，我们还证明了一种我们称之为手性传递力矩（Chirality transfer torque）的力矩，它施加在结点上，其值与横向手性电流有关。
{"title":"Chirality transfer torque and transverse Chirality current in the Dirac/magnetic Weyl semimetal junction","authors":"Morteza Salehi","doi":"10.1088/1402-4896/ad7547","DOIUrl":"https://doi.org/10.1088/1402-4896/ad7547","url":null,"abstract":"We theoretically show that an interface formed by a three-dimensional Dirac/magnetic Weyl semimetal deflects the propagation direction of hitting Weyl fermions according to their Chirality in opposite directions. This effect leads to a Chirality current that flows parallel to the interface. There is an imbalance between the Chirality of Weyl fermions in this current whereas it does not carry any charge. Also, this phenomenon creates an indirect gap in the charge conductance that pass through the circuit. Unlike real spin, Chirality remains a good quantum number in systems characterized by very strong spin-momentum coupling. We derive a continuity equation for the Chirality density wave to elucidate how magnetization alters its dynamics and relates to the transverse Chirality current. Furthermore, we demonstrate a torque, that we called it Chirality transfer torque, imposes on the junction that its value relates to the transverse Chirality current.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad741e
Dalton N Oliveira, Roman Chertovskih, Erico L Rempel and Francis F Franco
Transition to chaos and magnetic field generation are investigated in numerical simulations of three-dimensional rotating Rayleigh-Bénard convection. The behavior of the system is explored as a function of the rotation speed, measured by the Taylor number, the thermal buoyancy strength, measured by the Rayleigh number, and the magnetic Prandtl number. In the absence of magnetic field, a detailed exploration of the space of parameters reveals a sequence of Hopf bifurcations leading to quasiperiodicity and chaos. It is shown that rotation can dampen convection for low values of the Rayleigh number, but if buoyancy is strong enough to keep the convection, then rotation facilitates transition to chaos. In the presence of a weak seed magnetic field, convective motions may trigger a nonlinear dynamo that converts kinetic energy into magnetic energy, leading to an exponential increase of the magnetic energy. A nonhysteretic blowout bifurcation is shown to be responsible for the onset of the dynamo regime for a critical magnetic Prandtl number, whose value depends on the rotation rate.
{"title":"Transition to chaos in magnetized rotating Rayleigh-Bénard convection","authors":"Dalton N Oliveira, Roman Chertovskih, Erico L Rempel and Francis F Franco","doi":"10.1088/1402-4896/ad741e","DOIUrl":"https://doi.org/10.1088/1402-4896/ad741e","url":null,"abstract":"Transition to chaos and magnetic field generation are investigated in numerical simulations of three-dimensional rotating Rayleigh-Bénard convection. The behavior of the system is explored as a function of the rotation speed, measured by the Taylor number, the thermal buoyancy strength, measured by the Rayleigh number, and the magnetic Prandtl number. In the absence of magnetic field, a detailed exploration of the space of parameters reveals a sequence of Hopf bifurcations leading to quasiperiodicity and chaos. It is shown that rotation can dampen convection for low values of the Rayleigh number, but if buoyancy is strong enough to keep the convection, then rotation facilitates transition to chaos. In the presence of a weak seed magnetic field, convective motions may trigger a nonlinear dynamo that converts kinetic energy into magnetic energy, leading to an exponential increase of the magnetic energy. A nonhysteretic blowout bifurcation is shown to be responsible for the onset of the dynamo regime for a critical magnetic Prandtl number, whose value depends on the rotation rate.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad7546
V R Rasulov, R Ya Rasulov, M Kh Nasirov, I A Muminov and M M Mamatova
A theory of size quantization has been developed for both one-dimensional and zero-dimensional nanostructures, grown from monolayers of transition metal dichalcogenides. Expressions for the energy spectra of charge carriers have been obtained for both even and odd (relative to coordinate inversion) states in the quantum-confined line and point of monolayers of transition metal dichalcogenides, depending on their geometric dimensions. A numerical analysis of the quantum-confined energy states of electrons in nanostructures of monolayers of transition metal dichalcogenides has been conducted.
{"title":"Theory of size quantization in monolayers of transition metal dichalcogenides","authors":"V R Rasulov, R Ya Rasulov, M Kh Nasirov, I A Muminov and M M Mamatova","doi":"10.1088/1402-4896/ad7546","DOIUrl":"https://doi.org/10.1088/1402-4896/ad7546","url":null,"abstract":"A theory of size quantization has been developed for both one-dimensional and zero-dimensional nanostructures, grown from monolayers of transition metal dichalcogenides. Expressions for the energy spectra of charge carriers have been obtained for both even and odd (relative to coordinate inversion) states in the quantum-confined line and point of monolayers of transition metal dichalcogenides, depending on their geometric dimensions. A numerical analysis of the quantum-confined energy states of electrons in nanostructures of monolayers of transition metal dichalcogenides has been conducted.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad7331
Chi Gong, Xinyu Lu, Dakai Shang, Zhi Ren and Songtao Li
The electron–positron pair creation process during the Dirac vacuum breakdown triggered by strong external fields is analyzed. A frequency chirped, subcritical force field can significantly enhance the pair production yield under the identical total energy. This enhancement effect is caused by different chirp frequencies. We pay special attention to optimal field conditions as chirping parameter and phase of the time dependent field are varied. And the total number of created electrons with frequency weighted average under different chirp parameters are different from the theoretically calculated values. And no matter what the main mechanism is, the laser has the highest energy utilization rate when the electric field is symmetrical.
{"title":"Time domain optimization of pair production during vacuum breakdown triggered by frequency chirped external fields","authors":"Chi Gong, Xinyu Lu, Dakai Shang, Zhi Ren and Songtao Li","doi":"10.1088/1402-4896/ad7331","DOIUrl":"https://doi.org/10.1088/1402-4896/ad7331","url":null,"abstract":"The electron–positron pair creation process during the Dirac vacuum breakdown triggered by strong external fields is analyzed. A frequency chirped, subcritical force field can significantly enhance the pair production yield under the identical total energy. This enhancement effect is caused by different chirp frequencies. We pay special attention to optimal field conditions as chirping parameter and phase of the time dependent field are varied. And the total number of created electrons with frequency weighted average under different chirp parameters are different from the theoretically calculated values. And no matter what the main mechanism is, the laser has the highest energy utilization rate when the electric field is symmetrical.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad75c0
Jie Liu, Yue Cai, Kang-Jie Ma, Lei Tan and Wu-Ming Liu
We study the entanglement generation of two giant atoms within a one-dimensional bidirectional-chiral waveguide quantum electrodynamics (QED) system, where the initial state of the two giant atoms are ∣ea, gb〉. Here, each giant atom is coupled to the waveguide through three connection points, with the configurations divided into five types based on the arrangement of coupling points between the giant atoms and the waveguide: separate, fully braided, partially braided, fully nested, and partially nested. We explore the entanglement generation process within each configuration in both nonchiral and chiral coupling cases. It is demonstrated that entanglement can be controlled as needed by either adjusting the phase shift or selecting different configurations. For nonchiral coupling, the entanglement of each configuration exhibits steady state properties attributable to the presence of dark state. In addition, we find that steady-state entanglement can be obtained at more phase shifts in certain configurations by increasing the number of coupling points between the giant atoms and the bidirectional waveguide. In the case of chiral coupling, the entanglement is maximally enhanced compared to the one of nonchiral case. Especially in fully braided configuration, the concurrence reaches its peak value 1, which is robust to chirality. We further show the influence of atomic initial states on the evolution of interatomic entanglement. Our scheme can be used for entanglement generation in chiral quantum networks of giant-atom waveguide-QED systems, with potential applications in quantum networks and quantum communications.
{"title":"Entanglement enhancement of two giant atoms with multiple connection points in bidirectional-chiral quantum waveguide-QED system","authors":"Jie Liu, Yue Cai, Kang-Jie Ma, Lei Tan and Wu-Ming Liu","doi":"10.1088/1402-4896/ad75c0","DOIUrl":"https://doi.org/10.1088/1402-4896/ad75c0","url":null,"abstract":"We study the entanglement generation of two giant atoms within a one-dimensional bidirectional-chiral waveguide quantum electrodynamics (QED) system, where the initial state of the two giant atoms are ∣ea, gb〉. Here, each giant atom is coupled to the waveguide through three connection points, with the configurations divided into five types based on the arrangement of coupling points between the giant atoms and the waveguide: separate, fully braided, partially braided, fully nested, and partially nested. We explore the entanglement generation process within each configuration in both nonchiral and chiral coupling cases. It is demonstrated that entanglement can be controlled as needed by either adjusting the phase shift or selecting different configurations. For nonchiral coupling, the entanglement of each configuration exhibits steady state properties attributable to the presence of dark state. In addition, we find that steady-state entanglement can be obtained at more phase shifts in certain configurations by increasing the number of coupling points between the giant atoms and the bidirectional waveguide. In the case of chiral coupling, the entanglement is maximally enhanced compared to the one of nonchiral case. Especially in fully braided configuration, the concurrence reaches its peak value 1, which is robust to chirality. We further show the influence of atomic initial states on the evolution of interatomic entanglement. Our scheme can be used for entanglement generation in chiral quantum networks of giant-atom waveguide-QED systems, with potential applications in quantum networks and quantum communications.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad71ff
Qiuting Chen
In this paper we study a class of discrete quantum walks, known as bipartite walks. These include the well-known Grover’s walks. A discrete quantum walk is given by the powers of a unitary matrix U indexed by arcs or edges of the underlying graph. The walk is periodic if Uk = I for some positive integer k. Kubota has given a characterization of periodicity of Grover’s walk when the walk is defined on a regular bipartite graph with at most five eigenvalues. We extend Kubota’s results—if a biregular graph G has eigenvalues whose squares are algebraic integers with degree at most two, we characterize periodicity of the bipartite walk over G in terms of its spectrum. We apply periodicity results of bipartite walks to get a characterization of periodicity of Grover’s walk on regular graphs.
在本文中，我们研究了一类离散量子漫步，即所谓的二方漫步。其中包括著名的格罗弗漫步。离散量子漫步由以底层图的弧或边为索引的单元矩阵 U 的幂给出。当格罗弗漫步定义在最多有五个特征值的规则二方图上时，久保田给出了格罗弗漫步周期性的特征。我们扩展了久保田的结果--如果一个双线形图 G 的特征值的平方是代数整数，且最多有两个阶，那么我们就用它的谱来描述 G 上双线形行走的周期性。我们应用双方位行走的周期性结果，得到格罗弗行走在规则图上的周期性特征。
{"title":"Periodicity of bipartite walk on biregular graphs with conditional spectra","authors":"Qiuting Chen","doi":"10.1088/1402-4896/ad71ff","DOIUrl":"https://doi.org/10.1088/1402-4896/ad71ff","url":null,"abstract":"In this paper we study a class of discrete quantum walks, known as bipartite walks. These include the well-known Grover’s walks. A discrete quantum walk is given by the powers of a unitary matrix U indexed by arcs or edges of the underlying graph. The walk is periodic if Uk = I for some positive integer k. Kubota has given a characterization of periodicity of Grover’s walk when the walk is defined on a regular bipartite graph with at most five eigenvalues. We extend Kubota’s results—if a biregular graph G has eigenvalues whose squares are algebraic integers with degree at most two, we characterize periodicity of the bipartite walk over G in terms of its spectrum. We apply periodicity results of bipartite walks to get a characterization of periodicity of Grover’s walk on regular graphs.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad7414
R Amarnath, K S Bhargavi and S S Kubakaddi
Theoretically, we investigate the thermoelectric (TE) properties namely, electrical conductivity (σ), diffusion thermopower (Sd), power factor (PF), electronic thermal conductivity (κe) and thermoelectric figure of merit (ZT) for silicene on Al2O3 substrate. TE coefficients are obtained by solving the Boltzmann transport equation taking account of the electron scattering by all the relevant scattering mechanisms in silicene, namely charged impurity (CI), short-range disorder (SD), intra- and inter-valley acoustic (APs) and optical (OPs) phonons, and surface optical phonons (SOPs). The TE properties are numerically studied as a function of temperature T (2–400K) and electron concentration ns(0.1–10 × 1012 cm−2). The calculated σ and Sdare found to be governed by CIs at low temperatures (T< ∼ 10 K), similar to that in graphene. At higher T, they are found to be mainly dominated by the intra- and inter-valley APs. The resultant σ (Sd) is found to decrease (increase) with increasing T, whereas PF remains nearly constant for T> ∼ 100 K. On the other hand, ns dependence shows that σ (Sd) increases (decreases) with increasing ns; with PF relatively constant at lower ns and then decreases with increasing ns. At room temperature, the calculated σ (Sd) in silicene is closer to that in graphene and about an order of magnitude greater (less) than that in monolayer (ML) MoS2. The κe is found to be weakly depending on T and Wiedemann–Franz law is shown to be violated. We have predicted a maximum PF ∼3.5 mW m−1 K−2, at 300 K for ns = 0.1 × 1012 cm−2 from which the estimated ZT = 0.11, taking a theoretically predicted lattice thermal conductivity κl = 9.4 Wm−1 K−1, is a maximum. This ZT is much greater than that of graphene and ML MoS2. The ZT is found to decrease with the increasing ns. The ZT values for other values of ns in silicene, at 300 K, also show much superiority over graphene, thus making silicene a preferred thermoelectric material because of its relatively large σ and very small κl.
{"title":"Analytical study of the thermoelectric properties in silicene","authors":"R Amarnath, K S Bhargavi and S S Kubakaddi","doi":"10.1088/1402-4896/ad7414","DOIUrl":"https://doi.org/10.1088/1402-4896/ad7414","url":null,"abstract":"Theoretically, we investigate the thermoelectric (TE) properties namely, electrical conductivity (σ), diffusion thermopower (Sd), power factor (PF), electronic thermal conductivity (κe) and thermoelectric figure of merit (ZT) for silicene on Al2O3 substrate. TE coefficients are obtained by solving the Boltzmann transport equation taking account of the electron scattering by all the relevant scattering mechanisms in silicene, namely charged impurity (CI), short-range disorder (SD), intra- and inter-valley acoustic (APs) and optical (OPs) phonons, and surface optical phonons (SOPs). The TE properties are numerically studied as a function of temperature T (2–400K) and electron concentration ns(0.1–10 × 1012 cm−2). The calculated σ and Sdare found to be governed by CIs at low temperatures (T< ∼ 10 K), similar to that in graphene. At higher T, they are found to be mainly dominated by the intra- and inter-valley APs. The resultant σ (Sd) is found to decrease (increase) with increasing T, whereas PF remains nearly constant for T> ∼ 100 K. On the other hand, ns dependence shows that σ (Sd) increases (decreases) with increasing ns; with PF relatively constant at lower ns and then decreases with increasing ns. At room temperature, the calculated σ (Sd) in silicene is closer to that in graphene and about an order of magnitude greater (less) than that in monolayer (ML) MoS2. The κe is found to be weakly depending on T and Wiedemann–Franz law is shown to be violated. We have predicted a maximum PF ∼3.5 mW m−1 K−2, at 300 K for ns = 0.1 × 1012 cm−2 from which the estimated ZT = 0.11, taking a theoretically predicted lattice thermal conductivity κl = 9.4 Wm−1 K−1, is a maximum. This ZT is much greater than that of graphene and ML MoS2. The ZT is found to decrease with the increasing ns. The ZT values for other values of ns in silicene, at 300 K, also show much superiority over graphene, thus making silicene a preferred thermoelectric material because of its relatively large σ and very small κl.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1402-4896/ad7650
Cuimei Jiang, Xuejing Gu, Fangfang Zhang, Jian Liu and Pengfei Liu
The nonlinear circuit with charge-controlled memristor (CCM) can capture the external electric field effect. The nonlinear circuit with Josephson junction (JJ) can estimate the external magnetic field effect. Therefore, we propose an enhanced functional circuit by connecting a CCM and a JJ into a simple RLC nonlinear circuit. This enchanced circuit can estimate the external electromagnetic fields concurrently. The dynamical equations of the new memristive circuit and its Hamilton energy function are obtained by using the Kirchhoff’s law and the Helmholtz’s theorem. Furthermore, the complex dynamics of memristive circuit are investigated by applying bifurcation diagrams, Lyapunov exponents and time sampled series. The simulation experiment results indicate that the electromagnetic field has a great influence on complex dynamics of memristive circuit. In fact, this new nonlinear circuit is also a functional neural circuit, and it can be used to study the collective dynamic of functional neural network under the condition of an external electromagnetic fields.
{"title":"Dynamics of memristive circuit driven by Josephson junction","authors":"Cuimei Jiang, Xuejing Gu, Fangfang Zhang, Jian Liu and Pengfei Liu","doi":"10.1088/1402-4896/ad7650","DOIUrl":"https://doi.org/10.1088/1402-4896/ad7650","url":null,"abstract":"The nonlinear circuit with charge-controlled memristor (CCM) can capture the external electric field effect. The nonlinear circuit with Josephson junction (JJ) can estimate the external magnetic field effect. Therefore, we propose an enhanced functional circuit by connecting a CCM and a JJ into a simple RLC nonlinear circuit. This enchanced circuit can estimate the external electromagnetic fields concurrently. The dynamical equations of the new memristive circuit and its Hamilton energy function are obtained by using the Kirchhoff’s law and the Helmholtz’s theorem. Furthermore, the complex dynamics of memristive circuit are investigated by applying bifurcation diagrams, Lyapunov exponents and time sampled series. The simulation experiment results indicate that the electromagnetic field has a great influence on complex dynamics of memristive circuit. In fact, this new nonlinear circuit is also a functional neural circuit, and it can be used to study the collective dynamic of functional neural network under the condition of an external electromagnetic fields.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Metal oxide varistors (MOV) used for energy absorption branch in DC circuit breakers are complex enough to meet the requirements for small volume, light weight, and reliability in future high-voltage direct current (HVDC) grids. Therefore, a new energy absorption branch circuit that combines MOV and a liquid metal alloy energy absorber (LMEA) is proposed. Based on the constructed equivalent mathematical model of LMEA, the working principle and energy absorption process of MOV and LMEA in DC breaking process are analysed in PSCAD/EMTDC simulation software. Results demonstrate that LMEA, in contrast to MOV alone, absorbs 2.12 MJ of energy, constituting 35.6% of the total energy. Moreover, LMEA enhances energy dissipation density while reducing volume. Experimental analysis reveals MOV’s energy absorption mechanism via achieving residual voltage with ZnO varistor’s non-linear properties, swiftly transitioning from high to low resistance states to absorb energy. Conversely, LMEA relies on pulse current amplitude to initiate internal arcing, sharply increasing internal resistance for effective energy absorption. Experimental findings validate LMEA’s contribution of one-third of total energy absorption when pulse current amplitude reaches critical arcing threshold, consistent with simulation results. The results provide theoretical support for the engineering application of the new liquid metal alloy energy absorption in DC circuit breakers.
{"title":"A novel design of energy absorption branch for HVDC circuit breakers","authors":"Guoqiang Gao, Bingyan You, Yaguang Ma, Aozheng Wang, Wei Peng, Pengyu Qian, Yu Xiang, Zefeng Yang, Wenfu Wei and Guangning Wu","doi":"10.1088/1402-4896/ad75c3","DOIUrl":"https://doi.org/10.1088/1402-4896/ad75c3","url":null,"abstract":"Metal oxide varistors (MOV) used for energy absorption branch in DC circuit breakers are complex enough to meet the requirements for small volume, light weight, and reliability in future high-voltage direct current (HVDC) grids. Therefore, a new energy absorption branch circuit that combines MOV and a liquid metal alloy energy absorber (LMEA) is proposed. Based on the constructed equivalent mathematical model of LMEA, the working principle and energy absorption process of MOV and LMEA in DC breaking process are analysed in PSCAD/EMTDC simulation software. Results demonstrate that LMEA, in contrast to MOV alone, absorbs 2.12 MJ of energy, constituting 35.6% of the total energy. Moreover, LMEA enhances energy dissipation density while reducing volume. Experimental analysis reveals MOV’s energy absorption mechanism via achieving residual voltage with ZnO varistor’s non-linear properties, swiftly transitioning from high to low resistance states to absorb energy. Conversely, LMEA relies on pulse current amplitude to initiate internal arcing, sharply increasing internal resistance for effective energy absorption. Experimental findings validate LMEA’s contribution of one-third of total energy absorption when pulse current amplitude reaches critical arcing threshold, consistent with simulation results. The results provide theoretical support for the engineering application of the new liquid metal alloy energy absorption in DC circuit breakers.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the current era of increasing demand for optoelectronic-based devices with ultra-rapid response, it is important to understand the processes associated with the relaxation dynamics of hot carriers and transient electrical properties of WTe2 material under photoexcitation of charge carriers. In this work, using femtosecond laser pump–probe spectroscopy at room temperature we performed the transient absorption measurement on sputtered deposited WTe2 thin films having four different thicknesses to study dynamics associated with the relaxation of their hot carriers. The relaxation dynamics of photoexcited charge carriers undergo three exponential decay components associated with electron–phonon thermalization in the conduction band and phonon-assisted electron–hole recombination between the electron and hole pocket. The thickness-dependent investigation of WTe2 thin films reveals that the electron–hole recombination process is more prominent in thicker films than in thinner films, supporting previously published theoretical and experimental conclusions. The Ultrafast study of WTe2 thin films suggests that it is a suitable material for future ultrafast optoelectronic-based device applications.
{"title":"A room-temperature ultrafast carrier dynamical study and thickness-dependent investigation of WTe2 thin films on a flexible PET substrate","authors":"Sahil Verma, Kapil Kumar, Reena Yadav, Animesh Pandey, Mandeep Kaur, Mahesh Kumar and Sudhir Husale","doi":"10.1088/1402-4896/ad75d3","DOIUrl":"https://doi.org/10.1088/1402-4896/ad75d3","url":null,"abstract":"In the current era of increasing demand for optoelectronic-based devices with ultra-rapid response, it is important to understand the processes associated with the relaxation dynamics of hot carriers and transient electrical properties of WTe2 material under photoexcitation of charge carriers. In this work, using femtosecond laser pump–probe spectroscopy at room temperature we performed the transient absorption measurement on sputtered deposited WTe2 thin films having four different thicknesses to study dynamics associated with the relaxation of their hot carriers. The relaxation dynamics of photoexcited charge carriers undergo three exponential decay components associated with electron–phonon thermalization in the conduction band and phonon-assisted electron–hole recombination between the electron and hole pocket. The thickness-dependent investigation of WTe2 thin films reveals that the electron–hole recombination process is more prominent in thicker films than in thinner films, supporting previously published theoretical and experimental conclusions. The Ultrafast study of WTe2 thin films suggests that it is a suitable material for future ultrafast optoelectronic-based device applications.","PeriodicalId":20067,"journal":{"name":"Physica Scripta","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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