arXiv: Materials Science最新文献_第2页

Compositional effect on auto-oscillation behavior of Ni 100 −xFex/Pt spin Hall nano-oscillators 组分对Ni 100−xFex/Pt自旋霍尔纳米振荡器自振荡行为的影响

arXiv: Materials Science Pub Date : 2020-12-11 DOI: 10.1063/5.0035697

M. Haidar, H. Mazraati, P. Dürrenfeld, H. Fulara, M. Ranjbar, J. Åkerman

引用次数: 10

Dissipation-induced symmetry breaking: Emphanitic transitions in lead- and tin-containing chalcogenides and halide perovskites 耗散引起的对称性破缺:含铅和含锡的硫族化合物和卤化物钙钛矿中的强跃迁

arXiv: Materials Science Pub Date : 2020-12-10 DOI: 10.1063/5.0040056

K. Mukhuti, S. Sinha, S. Sinha, B. Bansal

{"title":"Dissipation-induced symmetry breaking: Emphanitic transitions in lead- and tin-containing chalcogenides and halide perovskites","authors":"K. Mukhuti, S. Sinha, S. Sinha, B. Bansal","doi":"10.1063/5.0040056","DOIUrl":"https://doi.org/10.1063/5.0040056","url":null,"abstract":"Lead and tin-based chalcogenide semiconductors like PbTe or SnSe have long been known to exhibit an unusually low thermal conductivity that makes them very attractive thermoelectric materials. An apparently unrelated fact is that the excitonic bandgap in these materials increases with temperature, whereas for most semiconductors one observes the opposite trend. These two anomalous features are also seen in a very different class of photovoltaic materials, namely the halide-perovskites such as CsPbBr3. It has been previously proposed that emphanisis, a local symmetry-breaking phenomenon, is the one common origin of these unusual features. Discovered a decade ago, emphanisis is the name given to the observed displacement of the lead or the tin ions from their cubic symmetry ground state to a locally distorted phase at high temperature. This phenomenon has been puzzling because it is unusual for the high-temperature state to be of a lower symmetry than the degenerate ground state. Motivated by the celebrated vibration-inversion resonance of the ammonia molecule, we propose a quantum tunneling-based model for emphanisis where decoherence is responsible for the local symmetry breaking with increasing temperature. From the analytic expression of the temperature dependence of the tunnel splitting (which serves as an order parameter), we provide three-parameter fitting formulae which capture the observed temperature dependence of the ionic displacements as well as the anomalous increase of the excitonic bandgap in all the relevant materials.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81439187","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}

引用次数: 3

Quantum spin Hall effect in Ta2M3Te5 (M=Pd,Ni) Ta2M3Te5 (M=Pd,Ni)中的量子自旋霍尔效应

arXiv: Materials Science Pub Date : 2020-12-10 DOI: 10.1103/PHYSREVB.103.115145

Zhaopeng Guo, D. Yan, Haohao Sheng, S. Nie, Youguo Shi, Zhijun Wang

{"title":"Quantum spin Hall effect in \u0000Ta2M3Te5\u0000 \u0000(M=Pd,Ni)","authors":"Zhaopeng Guo, D. Yan, Haohao Sheng, S. Nie, Youguo Shi, Zhijun Wang","doi":"10.1103/PHYSREVB.103.115145","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.115145","url":null,"abstract":"Quantum spin Hall (QSH) effect with great promise for the potential application in spintronics and quantum computing has attracted extensive research interest from both theoretical and experimental researchers. Here, we predict monolayer Ta$_2$Pd$_3$Te$_5$ can be a QSH insulator based on first-principles calculations. The interlayer binding energy in the layered van der Waals compound Ta$_2$Pd$_3$Te$_5$ is 19.6 meV/A$^2$; thus, its monolayer/thin-film structures could be readily obtained by exfoliation. The band inversion near the Fermi level ($E_F$) is an intrinsic characteristic, which happens between Ta-$5d$ and Pd-$4d$ orbitals without spin-orbit coupling (SOC). The SOC effect opens a global gap and makes the system a QSH insulator. With the $d$-$d$ band-inverted feature, the nontrivial topology in monolayer Ta$_2$Pd$_3$Te$_5$ is characterized by the time-reversal topological invariant $mathbb Z_2=1$, which is computed by the one-dimensional (1D) Wilson loop method as implemented in our first-principles calculations. The helical edge modes are also obtained using surface Green's function method. Our calculations show that the QSH state in Ta$_2M_3$Te$_5$ ($M=$ Pd, Ni) can be tuned by external strain. These monolayers and thin films provide feasible platforms for realizing QSH effect as well as related devices.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77691352","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}

引用次数: 7

Elimination of the linearization error in APW/LAPW basis set: Dirac-Kohn-Sham equations APW/LAPW基集线性化误差的消除:Dirac-Kohn-Sham方程

arXiv: Materials Science Pub Date : 2020-12-09 DOI: 10.1103/PHYSREVB.103.165101

A. Kutepov

{"title":"Elimination of the linearization error in APW/LAPW basis set: Dirac-Kohn-Sham equations","authors":"A. Kutepov","doi":"10.1103/PHYSREVB.103.165101","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.165101","url":null,"abstract":"A detailed account of the implementation of equations of the Relativistic Density Functional Theory (RDFT) using basis sets of APW/LAPW type with flexible extensions provided by local orbitals is given. Earlier discoveries of the importance of the High Derivative Local Orbital (HDLO) extension of APW/LAPW basis set for enhancing the accuracy of DFT calculations are confirmed using fully relativistic approach and $alpha$-U as an example. High Energy Local Orbitals (HELO's), however indispensable for GW calculations, are considerably less efficient in enhancing the accuracy of DFT applications. It is shown, that a simplified approach to the relativistic effects, namely, considering them only inside the muffin-tin (MT) spheres, produces basically identical results (as compared to fully relativistic approach) for the electronic free energy of the five materials considered in this work. By comparing the effect of the simplified approach on the electronic free energy with its effect on the electronic kinetic energy we conclude that the insensitivity of the free energy to the way we describe the relativistic effects in the interstitial region is related to the variational property of this quantity.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89157791","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}

引用次数: 4

High-throughput computational search for two-dimensional binary compounds: Energetic stability versus synthesizability of three-dimensional counterparts 二维二元化合物的高通量计算搜索:能量稳定性与三维对应物的合成能力

arXiv: Materials Science Pub Date : 2020-12-08 DOI: 10.1103/PHYSREVB.103.L121403

S. Ono, Honoka Satomi

引用次数: 11

Stress-controlled zero-field spin splitting in silicon carbide 碳化硅中应力控制的零场自旋分裂

arXiv: Materials Science Pub Date : 2020-12-08 DOI: 10.1063/5.0040936

I. Breev, A. Poshakinskiy, V. Yakovleva, S. Nagalyuk, E. N. Mokhov, R. Hübner, G. Astakhov, P. Baranov, A. Anisimov

引用次数: 7

Chemical Vapor Deposition Growth of Two-Dimensional Compound Materials: Controllability, Material Quality, and Growth Mechanism 二维复合材料的化学气相沉积生长:可控性、材料质量和生长机制

arXiv: Materials Science Pub Date : 2020-12-08 DOI: 10.1021/accountsmr.0c00063

Lei Tang, Junyang Tan, Huiyun Nong, Bilu Liu, Hui‐Ming Cheng

{"title":"Chemical Vapor Deposition Growth of Two-Dimensional Compound Materials: Controllability, Material Quality, and Growth Mechanism","authors":"Lei Tang, Junyang Tan, Huiyun Nong, Bilu Liu, Hui‐Ming Cheng","doi":"10.1021/accountsmr.0c00063","DOIUrl":"https://doi.org/10.1021/accountsmr.0c00063","url":null,"abstract":"CONSPECTUS: Two-dimensional (2D) compound materials are promising materials for use in electronics, optoelectronics, flexible devices, etc. because they are ultrathin and cover a wide range of properties. Among all methods to prepare 2D materials, chemical vapor deposition (CVD) is promising because it produces materials with a high quality and reasonable cost. So far, much efforts have been made to produce 2D compound materials with large domain size, controllable number of layers, fast-growth rate, and high quality features, etc. However, due to the complicated growth mechanism like sublimation and diffusion processes of multiple precursors, maintaining the controllability, repeatability, and high quality of CVD grown 2D binary and ternary materials is still a big challenge, which prevents their widespread use. Here, taking 2D transition metal dichalcogenides (TMDCs) as examples, we review current progress and highlight some promising growth strategies for the growth of 2D compound materials. The key technology issues which affect the CVD process, including non-metal precursor, metal precursor, substrate engineering, temperature, and gas flow, are discussed. Also, methods in improving the quality of CVD-grown 2D materials and current understanding on their growth mechanism are highlighted. Finally, challenges and opportunities in this field are proposed. We believe this review will guide the future design of controllable CVD systems for the growth of 2D compound materials with good controllability and high quality, laying the foundations for their potential applications.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82440611","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}

引用次数: 70

X-ray ptychographic topography: A robust nondestructive tool for strain imaging x射线平面形貌:应变成像的一种强大的非破坏性工具

arXiv: Materials Science Pub Date : 2020-12-06 DOI: 10.1103/PhysRevB.103.144107

M. Verezhak, S. Van Petegem, A. Rodriguez-Fernandez, P. Godard, Klaus Wakonig, D. Karpov, V. Jacques, A. Menzel, L. Thilly, A. Diaz

引用次数: 2

Anomalous Hall and Nernst effects in ferrimagnetic Mn4N films: Possible interpretations and prospects for enhancement 铁磁性Mn4N薄膜中的异常霍尔效应和能司特效应:可能的解释和增强前景

arXiv: Materials Science Pub Date : 2020-12-04 DOI: 10.1063/5.0039569

S. Isogami, K. Masuda, Y. Miura, N. Rajamanickam, Y. Sakuraba

{"title":"Anomalous Hall and Nernst effects in ferrimagnetic Mn4N films: Possible interpretations and prospects for enhancement","authors":"S. Isogami, K. Masuda, Y. Miura, N. Rajamanickam, Y. Sakuraba","doi":"10.1063/5.0039569","DOIUrl":"https://doi.org/10.1063/5.0039569","url":null,"abstract":"Ferrimagnetic Mn$_4$N is a promising material for heat flux sensors based on the anomalous Nernst effect (ANE) because of its sizable uniaxial magnetic anisotropy ($K_{rm u}$) and low saturation magnetization ($M_{rm s}$). We experimentally and theoretically investigated the ANE and anomalous Hall effect in sputter-deposited Mn$_4$N films. It was revealed that the observed negative anomalous Hall conductivity ($sigma_{xy}$) could be explained by two different coexisting magnetic structures, that is, a dominant magnetic structure with high $K_{rm u}$ contaminated by another structure with negligible $K_{rm u}$ owing to an imperfect degree of order of nitrogen. The observed transverse thermoelectric power ($S_{rm ANE}$) of $+0.5, mu{rm V/K}$ at $300, {rm K}$ gave a transverse thermoelectric coefficient ($alpha_{xy}$) of $+0.34, {rm A/(m cdot K)}$, which was smaller than the value predicted from first-principles calculation. The interpretation for $alpha_{xy}$ based on the first-principles calculations led us to conclude that the realization of single magnetic structure with high $K_{rm u}$ and optimal adjustment of the Fermi level are promising approaches to enhance $S_{rm ANE}$ in Mn$_4$N through the sign reversal of $sigma_{xy}$ and the enlargement of $alpha_{xy}$ up to a theoretical value of $1.77, {rm A/(m cdot K)}$.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90853317","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}

引用次数: 15

Revealing the Nanostructure of Mesoporous Fuel Cell Catalyst Supports for Durable, High-Power Performance 揭示介孔燃料电池催化剂支架的纳米结构，以实现耐用、高功率性能

arXiv: Materials Science Pub Date : 2020-12-04 DOI: 10.1149/1945-7111/ABE28E

M. Ko, Elliot Padgett, Venkata Yarlagadda, Anusorn Kongkanand, D. Muller

{"title":"Revealing the Nanostructure of Mesoporous Fuel Cell Catalyst Supports for Durable, High-Power Performance","authors":"M. Ko, Elliot Padgett, Venkata Yarlagadda, Anusorn Kongkanand, D. Muller","doi":"10.1149/1945-7111/ABE28E","DOIUrl":"https://doi.org/10.1149/1945-7111/ABE28E","url":null,"abstract":"Achieving high power performance and durability with low Pt loadings are critical challenges for proton exchange membrane fuel cells. PtCo catalysts developed on new carbon black supports show promise by simultaneously providing good oxygen reduction kinetics and local oxygen transport. We investigate the role of nanoscale morphology in the performance of these catalysts supported on accessible (HSC-e and HSC-f) and conventional (Ketjen Black) porous carbons using 3D electron tomography, nitrogen sorption, and electrochemical performance measurements. We find that the accessible porous carbons have hollow interiors with mesopores that are larger and more numerous than conventional porous carbons. However, mesopore-sized openings (>2nm width) are too rare to account for significant oxygen transport. Instead we propose the primary oxygen transport pathway into the interior is through 1-2nm microporous channels permeating the carbon. The increased mesoporosity in the accessible porous carbons results in a shorter diffusion pathlength through constrictive, tortuous micropores in the support shell leading to lower local oxygen transport resistance. In durability testing, the accessible porous carbons show faster rates of electrochemical surface area loss, likely from fewer constrictive pores that would mitigate coarsening, but maintain superior high current density performance at end of life from the improved local oxygen transport.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73034008","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}

引用次数: 14