Pub Date : 2022-05-24DOI: 10.3389/femat.2022.913280
Daniel P. Weller, D. Morelli
Thermoelectric materials have a long and storied history in the research and development of semiconductor materials, being the first such class of materials to be investigated. Thermoelectric may be used to convert heat to electricity or, alternatively, to liberate or absorb heat upon electrical excitation. They thus find application in thermoelectric generators for converting heat from a primary source or a waste stream to useful electrical power, and as solid state heating and cooling devices. In spite of their great potential in such important applications, thermoelectrics have suffered from a number of drawbacks that have hindered their utilization on a large scale. Chief among these is the fact that most high performance thermoelectric materials are comprised of elements that are in relatively low abundance. Additionally, their synthesis typically involves complex and multi-step processes, hindering manufacturability. Thermoelectric materials derived from Earth-abundant sources are thus of strong current interest, from both scientific and economic points of view. One of these, the family of semiconductors based on tetrahedrite compounds, has generated enormous interest over the last decade due to not only its potential low cost, but also for its fascinating science. In this review, we summarize the state of the art of tetrahedrite as a thermoelectric, with special emphasis on the relationship between crystal structure and bonding in the crystal and its unusually low lattice thermal conductivity; on its fascinating electronic structure; and on the wide array of compositions that have been synthesized and whose thermoelectric properties have been studied. We further highlight some rapid and facile synthesis techniques that have been developed for these compounds which, in combination with their potential low material cost, may open the door to widespread application of these fascinating materials.
{"title":"Tetrahedrite Thermoelectrics: From Fundamental Science to Facile Synthesis","authors":"Daniel P. Weller, D. Morelli","doi":"10.3389/femat.2022.913280","DOIUrl":"https://doi.org/10.3389/femat.2022.913280","url":null,"abstract":"Thermoelectric materials have a long and storied history in the research and development of semiconductor materials, being the first such class of materials to be investigated. Thermoelectric may be used to convert heat to electricity or, alternatively, to liberate or absorb heat upon electrical excitation. They thus find application in thermoelectric generators for converting heat from a primary source or a waste stream to useful electrical power, and as solid state heating and cooling devices. In spite of their great potential in such important applications, thermoelectrics have suffered from a number of drawbacks that have hindered their utilization on a large scale. Chief among these is the fact that most high performance thermoelectric materials are comprised of elements that are in relatively low abundance. Additionally, their synthesis typically involves complex and multi-step processes, hindering manufacturability. Thermoelectric materials derived from Earth-abundant sources are thus of strong current interest, from both scientific and economic points of view. One of these, the family of semiconductors based on tetrahedrite compounds, has generated enormous interest over the last decade due to not only its potential low cost, but also for its fascinating science. In this review, we summarize the state of the art of tetrahedrite as a thermoelectric, with special emphasis on the relationship between crystal structure and bonding in the crystal and its unusually low lattice thermal conductivity; on its fascinating electronic structure; and on the wide array of compositions that have been synthesized and whose thermoelectric properties have been studied. We further highlight some rapid and facile synthesis techniques that have been developed for these compounds which, in combination with their potential low material cost, may open the door to widespread application of these fascinating materials.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131586462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-16DOI: 10.3389/femat.2022.944873
E. Nica, S. Ran, L. Jiao, Q. Si
Symmetry breaking beyond a global U(1) phase is the key signature of unconventional superconductors. As prototypical strongly correlated materials, heavy-fermion metals provide ideal platforms for realizing unconventional superconductivity. In this article, we review heavy-fermion superconductivity, with a focus on those materials with multiple superconducting phases. In this context, we highlight the role of orbital-selective (matrix) pairing functions, which are defined as matrices in the space of effective orbital degrees of freedom such as electronic orbitals and sublattices as well as equivalent descriptions in terms of intra- and inter-band pairing components in the band basis. The role of quantum criticality and the associated strange-metal physics in the development of unconventional superconductivity is emphasized throughout. We discuss in some detail the recent experimental observations and theoretical perspectives in the illustrative cases of UTe2, CeRh2As2, and CeCu2Si2, where applied magnetic fields or pressure induce a variety of superconducting phases. We close by providing a brief overview of overarching issues and implications for possible future directions.
{"title":"Multiple superconducting phases in heavy-fermion metals","authors":"E. Nica, S. Ran, L. Jiao, Q. Si","doi":"10.3389/femat.2022.944873","DOIUrl":"https://doi.org/10.3389/femat.2022.944873","url":null,"abstract":"Symmetry breaking beyond a global U(1) phase is the key signature of unconventional superconductors. As prototypical strongly correlated materials, heavy-fermion metals provide ideal platforms for realizing unconventional superconductivity. In this article, we review heavy-fermion superconductivity, with a focus on those materials with multiple superconducting phases. In this context, we highlight the role of orbital-selective (matrix) pairing functions, which are defined as matrices in the space of effective orbital degrees of freedom such as electronic orbitals and sublattices as well as equivalent descriptions in terms of intra- and inter-band pairing components in the band basis. The role of quantum criticality and the associated strange-metal physics in the development of unconventional superconductivity is emphasized throughout. We discuss in some detail the recent experimental observations and theoretical perspectives in the illustrative cases of UTe2, CeRh2As2, and CeCu2Si2, where applied magnetic fields or pressure induce a variety of superconducting phases. We close by providing a brief overview of overarching issues and implications for possible future directions.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134285721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-10DOI: 10.3389/femat.2022.893797
Margaret R. Quinn, T. McQueen
Applying machine learning to aid the search for high temperature superconductors has recently been a topic of significant interest due to the broad applications of these materials but is challenging due to the lack of a quantitative microscopic model. Here we analyze over 33,000 entries from the Superconducting Materials Database, maintained by the National Institute for Materials Science of Japan, assigning crystal structures to each entry by correlation with Materials project and other structural databases. These augmented inputs are combined with material-specific properties, including critical temperature, to train convolutional neural networks (CNNs) to identify superconductors. Classification models achieve accuracy >95% and regression models trained to predict critical temperature achieve R2 >0.92 and mean absolute error ≈ 5.6 K. A crystal-graph representation whereby an undirected graph encodes atom sites (graph vertices) and their bonding relationships (graph edges), is used to represent materials’ periodic crystal structure to the CNNs. Trained networks are used to search though 130,000 crystal structures in the Materials Project for high temperature superconductor candidates and predict their critical temperature; several materials with model-predicted T C >30 K are proposed, including rediscovery of the recently explored infinite layer nickelates.
{"title":"Identifying New Classes of High Temperature Superconductors With Convolutional Neural Networks","authors":"Margaret R. Quinn, T. McQueen","doi":"10.3389/femat.2022.893797","DOIUrl":"https://doi.org/10.3389/femat.2022.893797","url":null,"abstract":"Applying machine learning to aid the search for high temperature superconductors has recently been a topic of significant interest due to the broad applications of these materials but is challenging due to the lack of a quantitative microscopic model. Here we analyze over 33,000 entries from the Superconducting Materials Database, maintained by the National Institute for Materials Science of Japan, assigning crystal structures to each entry by correlation with Materials project and other structural databases. These augmented inputs are combined with material-specific properties, including critical temperature, to train convolutional neural networks (CNNs) to identify superconductors. Classification models achieve accuracy >95% and regression models trained to predict critical temperature achieve R2 >0.92 and mean absolute error ≈ 5.6 K. A crystal-graph representation whereby an undirected graph encodes atom sites (graph vertices) and their bonding relationships (graph edges), is used to represent materials’ periodic crystal structure to the CNNs. Trained networks are used to search though 130,000 crystal structures in the Materials Project for high temperature superconductor candidates and predict their critical temperature; several materials with model-predicted T C >30 K are proposed, including rediscovery of the recently explored infinite layer nickelates.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132796553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-04DOI: 10.3389/femat.2022.891983
Ashutosh Mohapatra, M. Kar, S. Bhaumik
Recently, metal-halide perovskite nanocrystals (NCs) have shown major development and have attracted substantial interest in a wide range of applications, such as light-emitting diodes (LEDs), solar cells, lasers, and photodetectors due to their attractive properties, such as superior PL emission, a wider range of color tunability, narrow emission spectra, better color purity, low cost, easy solution-processability, and so on. In the past, many color-converting materials, such as III-nitrides, organics, polymers, metal chalcogenides, were investigated for solid-state lighting (SSL) white light-emitting diodes (WLEDs). Still, they suffer from issues such as low stability, low color rendering index (CRI), high correlated color temperature (CCT), low luminous efficiency (LE), and high cost. In this sense, metal-halide perovskite NCs exhibit a better color gamut compared with conventional lighting sources, and production costs are comparatively cheaper. Such materials may offer an upcoming substitute for future color-converting WLEDs. In this review, we discuss the metal halide perovskite NCs and their synthesis protocols. Then we elaborate on the recent progress of halide perovskite NCs as a conversion layer in the application of WLEDs.
{"title":"Recent Progress and Prospects on Metal Halide Perovskite Nanocrystals as Color Converters in the Fabrication of White Light-Emitting Diodes","authors":"Ashutosh Mohapatra, M. Kar, S. Bhaumik","doi":"10.3389/femat.2022.891983","DOIUrl":"https://doi.org/10.3389/femat.2022.891983","url":null,"abstract":"Recently, metal-halide perovskite nanocrystals (NCs) have shown major development and have attracted substantial interest in a wide range of applications, such as light-emitting diodes (LEDs), solar cells, lasers, and photodetectors due to their attractive properties, such as superior PL emission, a wider range of color tunability, narrow emission spectra, better color purity, low cost, easy solution-processability, and so on. In the past, many color-converting materials, such as III-nitrides, organics, polymers, metal chalcogenides, were investigated for solid-state lighting (SSL) white light-emitting diodes (WLEDs). Still, they suffer from issues such as low stability, low color rendering index (CRI), high correlated color temperature (CCT), low luminous efficiency (LE), and high cost. In this sense, metal-halide perovskite NCs exhibit a better color gamut compared with conventional lighting sources, and production costs are comparatively cheaper. Such materials may offer an upcoming substitute for future color-converting WLEDs. In this review, we discuss the metal halide perovskite NCs and their synthesis protocols. Then we elaborate on the recent progress of halide perovskite NCs as a conversion layer in the application of WLEDs.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130010797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-05-02DOI: 10.3389/femat.2022.875856
Quentin Weinbach, S. Thakkar, A. Carvalho, G. Chaplais, J. Combet, D. Constantin, N. Stein, D. Collin, Laure Biniek
In this study, we describe a reproducible process route to form highly mesoporous, mechanically robust and handleable aerogels based on entangled PEDOT:PSS nanofibers. The conservation of the alcogel 3D network is ensured via thorough control of the solvent exchange and drying steps. Particular consideration has been given to metrology, allowing us to fully characterize the thermoelectric properties of the aerogels. The interconnected fibrillar morphology provides good electrical conductivity and mechanical properties by forming effective pathways for both electron transfer and sustaining mechanical forces. The Seebeck coefficient does not seem to be impacted by the high porosity of the material. Finally, the positive impact of mesoporosity on thermal transport and in particular on the lattice part of the thermal conductivity (klat) is demonstrated here for the first time. Thus, this pure PEDOT:PSS aerogel exhibits very interesting structural and charge transport properties. The high power output of 2 µW, measured for a temperature gradient of 36.5 K on a single aerogel sample, highlights the possibility of integrating PEDOT:PSS aerogels into thermoelectric generators. Graphical Abstract
{"title":"Efficient Control of a Mesoporous Fibrillar PEDOT:PSS Aerogel Structure for Promising Thermoelectric Applications","authors":"Quentin Weinbach, S. Thakkar, A. Carvalho, G. Chaplais, J. Combet, D. Constantin, N. Stein, D. Collin, Laure Biniek","doi":"10.3389/femat.2022.875856","DOIUrl":"https://doi.org/10.3389/femat.2022.875856","url":null,"abstract":"In this study, we describe a reproducible process route to form highly mesoporous, mechanically robust and handleable aerogels based on entangled PEDOT:PSS nanofibers. The conservation of the alcogel 3D network is ensured via thorough control of the solvent exchange and drying steps. Particular consideration has been given to metrology, allowing us to fully characterize the thermoelectric properties of the aerogels. The interconnected fibrillar morphology provides good electrical conductivity and mechanical properties by forming effective pathways for both electron transfer and sustaining mechanical forces. The Seebeck coefficient does not seem to be impacted by the high porosity of the material. Finally, the positive impact of mesoporosity on thermal transport and in particular on the lattice part of the thermal conductivity (klat) is demonstrated here for the first time. Thus, this pure PEDOT:PSS aerogel exhibits very interesting structural and charge transport properties. The high power output of 2 µW, measured for a temperature gradient of 36.5 K on a single aerogel sample, highlights the possibility of integrating PEDOT:PSS aerogels into thermoelectric generators. Graphical Abstract","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126537550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-19DOI: 10.3389/femat.2022.849879
D. F. Falcone, M. Halter, L. Bégon-Lours, B. Offrein
Building Artificial Neural Network accelerators by implementing the vector-matrix multiplication in the analog domain relies on the development of non-volatile and tunable resistances. In this work, we describe the nanofabrication of a three-dimensional HZO—WOx Fin Ferroelectric Field Effect Transistor (FinFeFET) with back-end-of-line conditions. The metal-oxide channel (WOx) is structured into fins and engineered such that: 1) the current-voltage characteristic is linear (Ohmic conduction) and 2) the carrier density is small enough such that the screening length is comparable to one dimension of the device. The process temperature, including the HZO crystallization, does not exceed 400°C. Resistive switching is demonstrated in FinFeFET devices with fins dimension as small as 10 nm wide and 200 nm long. Devices containing a single fin that are 10 nm wide are characterized: 5 µs long voltage pulses in the range (−5.5 and 5 V) are applied on the gate, resulting in analog and symmetric long term potentiation and depression with linearity coefficients of 1.2 and −2.5.
{"title":"Back-End, CMOS-Compatible Ferroelectric FinFET for Synaptic Weights","authors":"D. F. Falcone, M. Halter, L. Bégon-Lours, B. Offrein","doi":"10.3389/femat.2022.849879","DOIUrl":"https://doi.org/10.3389/femat.2022.849879","url":null,"abstract":"Building Artificial Neural Network accelerators by implementing the vector-matrix multiplication in the analog domain relies on the development of non-volatile and tunable resistances. In this work, we describe the nanofabrication of a three-dimensional HZO—WOx Fin Ferroelectric Field Effect Transistor (FinFeFET) with back-end-of-line conditions. The metal-oxide channel (WOx) is structured into fins and engineered such that: 1) the current-voltage characteristic is linear (Ohmic conduction) and 2) the carrier density is small enough such that the screening length is comparable to one dimension of the device. The process temperature, including the HZO crystallization, does not exceed 400°C. Resistive switching is demonstrated in FinFeFET devices with fins dimension as small as 10 nm wide and 200 nm long. Devices containing a single fin that are 10 nm wide are characterized: 5 µs long voltage pulses in the range (−5.5 and 5 V) are applied on the gate, resulting in analog and symmetric long term potentiation and depression with linearity coefficients of 1.2 and −2.5.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125699373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-07DOI: 10.3389/femat.2022.861448
G. Chappell, W. Nelson, D. Graf, R. Baumbach
Studies that control the unit cell volume and electronic composition have been useful in revealing what factors lead to hidden order and superconductivity in the strongly correlated electron system URu2Si2. For example, isoelectronic tuning that increases the hybridization between the f and conduction electron states (i.e., applied pressure and Ru → Fe/Os chemical substitution) 1) converts hidden order into antiferromagnetism and 2) destroys the superconductivity. The impact of nonisoelectronic chemical substitution has been less clear, but several unifying trends have recently emerged for chemical substitution vectors that qualitatively add electrons (e.g., Ru → Rh/Ir and Si → P). This includes 1) the rapid destruction of hidden order and superconductivity, 2) composition regions where the underlying Kondo lattice is preserved but does not harbor an ordered state, and 3) the emergence of complex magnetism at large substitutions. In order to assess the limits of this perspective, we have investigated the series U(Ru1−x Pt x )2Si2 for x ≲ 0.19, where the Ru and Pt d-shells differ substantially from each other. Magnetic susceptibility, electrical resistivity, and heat capacity measurements unexpectedly reveal a phase diagram with notable similarities to those of other electron doping series. This result reinforces the viewpoint that there is a quasi-universal affect that results from electron doping in this material, and we anticipate that an understanding of these trends will be useful to isolate what factors are foundational for hidden order and superconductivity.
{"title":"Electronic Tuning in URu2Si2 Through Ru to Pt Chemical Substitution","authors":"G. Chappell, W. Nelson, D. Graf, R. Baumbach","doi":"10.3389/femat.2022.861448","DOIUrl":"https://doi.org/10.3389/femat.2022.861448","url":null,"abstract":"Studies that control the unit cell volume and electronic composition have been useful in revealing what factors lead to hidden order and superconductivity in the strongly correlated electron system URu2Si2. For example, isoelectronic tuning that increases the hybridization between the f and conduction electron states (i.e., applied pressure and Ru → Fe/Os chemical substitution) 1) converts hidden order into antiferromagnetism and 2) destroys the superconductivity. The impact of nonisoelectronic chemical substitution has been less clear, but several unifying trends have recently emerged for chemical substitution vectors that qualitatively add electrons (e.g., Ru → Rh/Ir and Si → P). This includes 1) the rapid destruction of hidden order and superconductivity, 2) composition regions where the underlying Kondo lattice is preserved but does not harbor an ordered state, and 3) the emergence of complex magnetism at large substitutions. In order to assess the limits of this perspective, we have investigated the series U(Ru1−x Pt x )2Si2 for x ≲ 0.19, where the Ru and Pt d-shells differ substantially from each other. Magnetic susceptibility, electrical resistivity, and heat capacity measurements unexpectedly reveal a phase diagram with notable similarities to those of other electron doping series. This result reinforces the viewpoint that there is a quasi-universal affect that results from electron doping in this material, and we anticipate that an understanding of these trends will be useful to isolate what factors are foundational for hidden order and superconductivity.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129406794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-29DOI: 10.3389/femat.2022.869803
Zhijun Jiang, Bin Xu, S. Prosandeev, J. Íñiguez, H. Xiang, L. Bellaiche
Dielectric capacitors are particularly suitable to store the electrical energy of a fast-changing nature. Here, we present a review of recent applications of first principles and first-principles-based effective Hamiltonian approaches to the study of energy storage in ferroelectrics, lead-free antiferroelectrics, relaxor ferroelectrics, and nitride semiconductors. Specifically, these approaches are used to investigate the energy density and efficiency in perovskite BaTiO3, PbTiO3, and KNbO3 ferroelectrics; Bi1−x R x FeO3 antiferroelectric solid solutions (where R is a rare-earth ion); Ba(Zr,Ti)O3 relaxor ferroelectrics; and epitaxial AlN/ScN superlattices. Ultrahigh energy densities and efficiencies are predicted in some of these compounds. In addition, phenomenological models are used to analyze and understand these energy storage results. Consequently, the numerical methods and simple models detailed here can be easily employed to design novel nonlinear dielectrics with further enhanced energy storage performance.
介电电容器特别适合储存快速变化的电能。在这里，我们回顾了第一原理和基于第一原理的有效哈密顿方法在铁电体、无铅反铁电体、弛豫铁电体和氮化半导体中储能研究的最新应用。具体来说，这些方法被用于研究钙钛矿BaTiO3、PbTiO3和KNbO3铁电体的能量密度和效率;Bi1−x R x FeO3反铁电固溶体(R为稀土离子);Ba(Zr,Ti)O3弛豫铁电体;外延AlN/ScN超晶格。预测其中一些化合物具有超高的能量密度和效率。此外，还采用了现象学模型来分析和理解这些储能结果。因此，本文详细介绍的数值方法和简单模型可以很容易地用于设计具有进一步增强储能性能的新型非线性电介质。
{"title":"Electrical Energy Storage From First Principles","authors":"Zhijun Jiang, Bin Xu, S. Prosandeev, J. Íñiguez, H. Xiang, L. Bellaiche","doi":"10.3389/femat.2022.869803","DOIUrl":"https://doi.org/10.3389/femat.2022.869803","url":null,"abstract":"Dielectric capacitors are particularly suitable to store the electrical energy of a fast-changing nature. Here, we present a review of recent applications of first principles and first-principles-based effective Hamiltonian approaches to the study of energy storage in ferroelectrics, lead-free antiferroelectrics, relaxor ferroelectrics, and nitride semiconductors. Specifically, these approaches are used to investigate the energy density and efficiency in perovskite BaTiO3, PbTiO3, and KNbO3 ferroelectrics; Bi1−x R x FeO3 antiferroelectric solid solutions (where R is a rare-earth ion); Ba(Zr,Ti)O3 relaxor ferroelectrics; and epitaxial AlN/ScN superlattices. Ultrahigh energy densities and efficiencies are predicted in some of these compounds. In addition, phenomenological models are used to analyze and understand these energy storage results. Consequently, the numerical methods and simple models detailed here can be easily employed to design novel nonlinear dielectrics with further enhanced energy storage performance.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123590670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-03DOI: 10.3389/femat.2022.869495
E. Schuberth, S. Wirth, F. Steglich
The tetragonal heavy-fermion metal YbRh2Si2 orders antiferromagnetically at T N = 70 mK and exhibits an unconventional quantum critical point (QCP) of Kondo-destroying type at B N = 60 mT, for the magnetic field applied within the basal (a, b) plane. Ultra-low-temperature magnetization and heat-capacity measurements at very low fields indicate that the 4f-electronic antiferromagnetic (AF) order is strongly suppressed by a nuclear-dominated hybrid order (“A-phase”) at T A ≤ 2.3 mK, such that quantum critical fluctuations develop at B ≈ 0 (Schuberth et al., Science, 2016, 351, 485–488). This enables the onset of heavy-fermion superconductivity (T c = 2 mK) which appears to be suppressed by the primary antiferromagnetic order at elevated temperatures. Measurements of the Meissner effect reveal bulk superconductivity, with T c decreasing under applied field to T c < 1 mK at B > 20 mT. The observation of a weak but distinct superconducting shielding signal at a temperature as high as 10 mK suggests the formation of insulated random islands with emergent A-phase order and superconductivity. Upon cooling, the shielding signal increases almost linearly in temperature, indicating a growth of the islands which eventually percolate at T ≈ 6.5 mK. Recent electrical-resistivity results by Nguyen et al. (Nat. Commun., 2021, 12, 4341) confirm the existence of superconductivity in YbRh2Si2 at ultra-low temperatures. The combination of the results of Schuberth et al. (2016) and Nguyen et al. (2021) at ultra-low temperatures below B N, along with those previously established at higher temperatures in the paramagnetic state, provide compelling evidence that the Kondo-destruction quantum criticality robustly drives unconventional superconductivity.
四边形重费米子金属YbRh2Si2在T N = 70 mK时呈反铁磁序排列，在B N = 60 mT时表现出近道毁灭型的非常规量子临界点(QCP)。在极低磁场下的超低温磁化和热容测量表明，在T a≤2.3 mK时，4f电子反铁磁(AF)序被核主导的杂化序(“a相”)强烈抑制，使得量子临界涨落在B≈0时发生(Schuberth等人，Science, 2016, 351,485 - 488)。这使得重费米子超导性(T c = 2 mK)在高温下似乎被初级反铁磁序抑制。Meissner效应的测量结果表明，当温度> 20 mT时，温度c随电场的增大而减小，温度c < 1 mK。在温度高达10 mK时，观察到微弱但明显的超导屏蔽信号，表明形成了具有涌现a相秩序和超导性的绝缘随机岛。冷却后，屏蔽信号在温度上几乎呈线性增加，表明在T≈6.5 mK时最终渗透的岛的增长。Nguyen等人(Nat. Commun.)最近的电阻率结果。(2012,12, 4341)证实了YbRh2Si2在超低温下存在超导性。Schuberth等人(2016)和Nguyen等人(2021)在低于B N的超低温下的结果，以及之前在顺磁状态下更高温度下建立的结果，提供了令人信服的证据，证明近道破坏量子临界性有力地驱动了非常规超导性。
{"title":"Nuclear-Order-Induced Quantum Criticality and Heavy-Fermion Superconductivity at Ultra-low Temperatures in YbRh2Si2","authors":"E. Schuberth, S. Wirth, F. Steglich","doi":"10.3389/femat.2022.869495","DOIUrl":"https://doi.org/10.3389/femat.2022.869495","url":null,"abstract":"The tetragonal heavy-fermion metal YbRh2Si2 orders antiferromagnetically at T N = 70 mK and exhibits an unconventional quantum critical point (QCP) of Kondo-destroying type at B N = 60 mT, for the magnetic field applied within the basal (a, b) plane. Ultra-low-temperature magnetization and heat-capacity measurements at very low fields indicate that the 4f-electronic antiferromagnetic (AF) order is strongly suppressed by a nuclear-dominated hybrid order (“A-phase”) at T A ≤ 2.3 mK, such that quantum critical fluctuations develop at B ≈ 0 (Schuberth et al., Science, 2016, 351, 485–488). This enables the onset of heavy-fermion superconductivity (T c = 2 mK) which appears to be suppressed by the primary antiferromagnetic order at elevated temperatures. Measurements of the Meissner effect reveal bulk superconductivity, with T c decreasing under applied field to T c < 1 mK at B > 20 mT. The observation of a weak but distinct superconducting shielding signal at a temperature as high as 10 mK suggests the formation of insulated random islands with emergent A-phase order and superconductivity. Upon cooling, the shielding signal increases almost linearly in temperature, indicating a growth of the islands which eventually percolate at T ≈ 6.5 mK. Recent electrical-resistivity results by Nguyen et al. (Nat. Commun., 2021, 12, 4341) confirm the existence of superconductivity in YbRh2Si2 at ultra-low temperatures. The combination of the results of Schuberth et al. (2016) and Nguyen et al. (2021) at ultra-low temperatures below B N, along with those previously established at higher temperatures in the paramagnetic state, provide compelling evidence that the Kondo-destruction quantum criticality robustly drives unconventional superconductivity.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123755983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-02DOI: 10.3389/femat.2022.851294
Hongtao Liu, C. Hsieh, Ya-Mei He, Chu‐Chen Chueh, Zhong’an Li
Currently, the two exocyclic vinyl bridges in the acceptor–donor–acceptor (A–D–A)-type nonfullerene acceptors (NFAs) have been widely recognized as one of the most vulnerable sites under external stresses. Embedding the exocyclic vinyl bridges into an aromatic ring could be a feasible solution to stabilize them. Herein, we successfully develop a phenalene-locked vinyl bridge via a titanium tetrachloride—pyridine catalytic Knoevenagel condensation, to synthesize two new A–D–A-type unfused NFAs, EH-FPCN and O-CPCN, wherein malononitrile is used as the electron-deficient terminal group while fluorene and carbazole rings are used as the electron-rich cores, respectively. These two NFAs possess wide bandgaps associated with deep energy levels, and significantly enhanced chemical and photochemical stabilities compared to the analogue molecule O-CzCN with normal exocyclic vinyl bridges. When pairing with a narrow bandgap polymer donor PTB7-Th, the fabricated EH-FPCN- and O-CPCN-based organic solar cells achieved power conversion efficiencies of 0.91 and 1.62%, respectively. The higher efficiencies for O-CPCN is attributed to its better film morphology and higher electron mobility in the blend film. Overall, this work provides a new design strategy to stabilize the vulnerable vinyl bridges of A–D–A-type NFAs.
{"title":"Phenalene—A New Ring-Locked Vinyl Bridge for Nonfullerene Acceptors With Enhanced Chemical and Photochemical Stabilities","authors":"Hongtao Liu, C. Hsieh, Ya-Mei He, Chu‐Chen Chueh, Zhong’an Li","doi":"10.3389/femat.2022.851294","DOIUrl":"https://doi.org/10.3389/femat.2022.851294","url":null,"abstract":"Currently, the two exocyclic vinyl bridges in the acceptor–donor–acceptor (A–D–A)-type nonfullerene acceptors (NFAs) have been widely recognized as one of the most vulnerable sites under external stresses. Embedding the exocyclic vinyl bridges into an aromatic ring could be a feasible solution to stabilize them. Herein, we successfully develop a phenalene-locked vinyl bridge via a titanium tetrachloride—pyridine catalytic Knoevenagel condensation, to synthesize two new A–D–A-type unfused NFAs, EH-FPCN and O-CPCN, wherein malononitrile is used as the electron-deficient terminal group while fluorene and carbazole rings are used as the electron-rich cores, respectively. These two NFAs possess wide bandgaps associated with deep energy levels, and significantly enhanced chemical and photochemical stabilities compared to the analogue molecule O-CzCN with normal exocyclic vinyl bridges. When pairing with a narrow bandgap polymer donor PTB7-Th, the fabricated EH-FPCN- and O-CPCN-based organic solar cells achieved power conversion efficiencies of 0.91 and 1.62%, respectively. The higher efficiencies for O-CPCN is attributed to its better film morphology and higher electron mobility in the blend film. Overall, this work provides a new design strategy to stabilize the vulnerable vinyl bridges of A–D–A-type NFAs.","PeriodicalId":119676,"journal":{"name":"Frontiers in Electronic Materials","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123443668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：