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Cr-Cr distance and magnetism in the phase diagram of triangular lattice antiferromagnets: A systematic comparative study

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Physical Review Materials 2024年第8期8卷 084403-084403页

作者： E. Nocerino J. Sugiyama O. K. Forslund I. Umegaki S. Kobayashi K. Yoshimura Y. Sassa M. Månsson Department of Applied Physics Comprehensive Research Organization for Science and Society (CROSS) Tokai Ibaraki 319-1106 Japan Advanced Science Research Center Physik-Institut Department of Physics and Astronomy Muon Science Laboratory (JASRI) 1-1-1 Kouto Sayo 679-5198 Japan Department of Chemistry Graduate School of Science Department of Energy and Hydrocarbon Chemistry Graduate School of Engineering

In this study, we investigate the influence of Cr-Cr distances on the magnetic properties of triangular lattice antiferromagnets through the lens of the recently synthesized Cr compounds LiCrSe2, LiCrTe2, and NaCrTe2. Our comprehensive analysis integrates existing magnetic structure data and new insights from muon spin rotation measurements, revealing a striking mutual influence between strongly correlated electrons and structural degrees of freedom in systems possessing very different magnetic properties despite having the same crystal symmetry. In particular, we delineate how Cr-Cr distances specifically dictate the magnetic behaviors of the triangular lattice antiferromagnets LiCrSe2, LiCrTe2, and NaCrTe2. By crafting phase diagrams based on these distances, we establish a clear correlation between the structural parameters and the magnetic ground states of these materials together with a wide variety of trivalent Cr triangular lattice layered magnets. Our analysis uncovers a transition range for in-plane and out-of-plane Cr-Cr distances that demarcates distinct magnetic behaviors, highlighting the nuanced role of lattice geometry in the spin-lattice interaction and electron correlation dynamics.

关键词： Antiferromagnetism Exchange interaction Frustrated magnetism Magnetic phase transitions Magnetism Magnetoelastic effect

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Vibrational entropies of oxygen vacancy formation in metal oxides

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Physical Review Materials 2024年第5期8卷 055407-055407页

作者： Bianca Baldassarri Jiangang He Christopher Wolverton Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA

Oxygen vacancies play a key role in many energy-related applications, and the investigation of the thermodynamic forces driving their formation across different materials can be tackled through the use of ab initio methods. In this context, however, computational studies targeting finite-temperature properties such as entropy remain scarce. Wider-ranging studies are of interest to deepen the understanding of the role of the entropy of oxygen vacancy formation and its different components in processes like the ones involved in solar thermochemical hydrogen (STCH) production, and to investigate the existence of common trends and differences between materials. In this work, we use density functional theory and harmonic phonon calculations to compute the vibrational entropy of oxygen vacancy formation (ΔSvib) for 10 different metal oxide compounds. The computation is carried out by taking the difference between the vibrational entropy of a vacancy-containing and a pristine structure, while the entropic contribution from the final gaseous state of the oxygen lost from the material is accounted for separately with a gas entropy term. We first examine the temperature dependence of ΔSvib and highlight the presence of an initial peak around room temperature, followed by a steady decrease resulting from the presence of an additional O atom (the one becoming vacant) in the defect-free structure. We then inspect the atomic contributions to ΔSvib, and highlight similarities and differences between compounds. Finally, we consider other significant sources of entropy, and find ΔSvib to provide a smaller, yet non-negligible, contribution to the total entropy of vacancy formation. We also compare the temperature dependence of ΔSvib to that of the gas entropy, and show that the two largely counterbalance each other at high temperatures.

关键词： Entropy Hydrogen production Density functional theory

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Cascaded-Type Band Alignment of a WBG Perovskite/NBG Perovskite For Heterostructure Solar Cells

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ACS applied Energy Materials 2024年第8期7卷 3039-3048页

作者： Thakran, Anjali Mohapatra, Anisha Verma, Hemant Hofmann, Mario Ansari, Zeeshan Alam Hanmandlu, Chintam Lu, Chung Hsin Chu, Chih Wei Department of Physics National Taiwan University Taipei106 Taiwan Research Center for Applied Sciences Academia Sinica 128 Academia Road Section 2 Nangang Taipei11529 Taiwan Nano-Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei106 Taiwan Department of Chemical Engineering National Taiwan University Taipei106 Taiwan Department of Photonics National Yang Ming Chiao Tung University Hsinchu City30010 Taiwan College of Engineering Center for Green Technology Chang Gung University Taoyuan City333002 Taiwan

The performance of single-junction mixed-halide perovskite-based solar cells is limited by thermalization and spectral losses. With advanced device architectures, the perovskite/perovskite heterostructure, where two or more photoactive layers are stacked together, can help to minimize these losses. In this work, we conformally transfer printed a narrow-band-gap perovskite over a spin-coated wide-band-gap perovskite layer to form a perovskite/perovskite heterostructure. This heterostructure results in broader spectral coverage and the higher position of the lowest unoccupied molecular orbital (LUMO) level of MAPbBrxI3-x compared to MA0.7FA0.3Pb0.5Sn0.5I3, forming a cascaded energy level alignment between photoactive layers. Additionally, direct evidence of improved morphology has been observed with the transfer-printing technique in heterostructure formation. The bottom layer provides favorable assistance for the growth of the top perovskite near the interface with good coverage and maintains the quality of the film. Thus, the increased crystallinity and reduced grain boundaries lead to less defects. This reduction played a key role in suppressing recombination losses at the interfaces, ultimately leading to improved device performance. These inherent properties have a positive impact on the photovoltaic response of the device, resulting in broader spectral response and power conversion efficiencies (PCEs) of 14.76% in the heterostructure device. A notable improvement is achieved compared to control single-junction devices, which typically have a PCE of nearly 10% with printed-Sn and 12% with spin-Br-based devices. Moreover, the heterostructure-based device exhibits high stability, retaining almost 80% of its initial PCE value for almost 1000 h with proper encapsulation. Our technique can be utilized for designing low-temperature and solution-processed stacked layers, applicable for optoelectronic devices, including light-emitting diodes (LEDs), sensors, and transist

关键词： Perovskite

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Effect of Ti3AlC2 MAX phase on electrochemical performance of thermo-responsive copolymer electrolyte for solid state zinc-ion battery

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Materials Science for Energy Technologies 2024年第1期7卷 237-248页

作者： Dueramae, Isala Okhawilai, Manunya Kasemsiri, Pornnapa Uyama, Hiroshi Kita, Rio Metallurgy and Materials Science Research Institute Chulalongkorn University Bangkok10330 Thailand Center of Excellence in Responsive Wearable Materials Chulalongkorn University Bangkok10330 Thailand Sustainable Infrastructure Research and Development Center Department of Chemical Engineering Faculty of Engineering Khon Kaen University Khon Kaen40002 Thailand Department of Applied Chemistry Graduate School of Engineering Osaka University Osaka565-0871 Japan Department of Physics Tokai University Kanagawa259-1292 Japan

The solid-state zinc-ion battery (ZIB) is environmentally friendly, cost effective, and extremely safe, which are essential features for alternative sustainable energy storage systems. Herein, a polymer composite electrolyte (PCE) is successfully developed through a facile solution-casting approach from a thermo-responsive copolymer-based electrolyte and layered ternary carbide (Ti3AlC2). The thermo-responsive copolymer demonstrated synergistic mechanical properties through the addition of an appropriate plasticizer and a zinc salt. This combination suggests that the material possesses thermal self-protection capabilities due to its anti-Arrhenius ionic-conducting behavior. However, parasitic reactions and dendrite formation hindered the achievement of its full potential. The incorporation of Ti3AlC2 or MAX phase can mitigate the above obstacles, enhancing electrochemical performance with excellent flexibility and maintainable self-extinguishing. The solid-state ZIB benefits from the well-designed PCE with the expanding layer interspacing, delivering a remarkably high capacity (336 mAh g−1 at 0.1 A g−1) and energy density of 242 Wh kg−1. This is achieved due to the Ti3AlC2′s ability to immobilize or entrap triflate anions via electrostatic forces. Therefore, the designed PCE is a promising step toward the development of flexible solid electrolytes in ZIBs. © 2023

关键词： Cost effectiveness

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Intrinsic magnetism in KTaO3 heterostructures

arXiv

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arXiv 2024年

作者： Krantz, Patrick W. Tyner, Alexander Goswami, Pallab Chandrasekhar, Venkat Department of Physics Northwestern University EvanstonIL60208 United States Graduate Program for Applied Physics Northwestern University EvanstonIL60208 United States

There has been intense recent interest in the two-dimensional electron gases (2DEGs) that form at the surfaces and interfaces of KTaO3 (KTO), with the discovery of superconductivity at temperatures significantly higher than those of similar 2DEGs based on SrTiO3 (STO). Like STO heterostructures, these KTO 2DEGs are formed by depositing an overlayer on top of appropriately prepared KTO surfaces. Some of these overlayers are magnetic, and the resulting 2DEGs show signatures of this magnetism, including hysteresis in the magnetoresistance (MR). Here we show that KTO 2DEGs fabricated by depositing AlOx on top of KTO also show hysteretic MR, indicative of long range magnetic order, even though the samples nominally contain no intrinsic magnetic elements. The hysteresis appears in both the transverse and longitudinal resistance in magnetic fields both perpendicular to and in the plane of the 2DEG. The hysteretic MR has different characteristic fields and shapes for surfaces of different crystal orientations, and vanishes above a few Kelvin. Density functional theory (DFT) calculations indicate that the magnetism likely arises from Ta4+ local moments created in the presence of oxygen vacancies. © 2024, CC BY-NC-ND.

关键词： Strontium titanates

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Nonlinear Hall Effect in KTaO3Two-Dimensional Electron Gases

arXiv

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arXiv 2024年

The observation of a Hall effect, a finite transverse voltage induced by a longitudinal current, usually requires the breaking of time-reversal symmetry, for example through the application of an external magnetic field or the presence of long range magnetic order in a sample. Recently it was suggested that under certain symmetry conditions, the presence of finite Berry curvatures in the band structure of a system with time-reversal symmetry but without inversion symmetry can give rise to a nonlinear Hall effect in the presence of a probe current. In order to observe the nonlinear Hall effect, one requires a finite component of a so-called Berry dipole along the direction of the probe current. We report here measurements of the nonlinear Hall effect in two-dimensional electron gases fabricated on the surface of KTaO3with different surface crystal orientations as a function of the probe current, a transverse electric field and back gate voltage. For all three crystal orientations, the transverse electric field modifies the nonlinear Hall effect. We discuss our results in the context of the current understanding of the nonlinear Hall effect as well as potential experimental artifacts that may give rise to the same effects. © 2024, CC BY-NC-SA.

关键词： Crystal orientation

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Direct Observation of Early-Stage Polymer Crystallization Driven by Surface Wrinkling and Compressive Stress in Thin Films

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Chinese Journal of Polymer Science 2025年第2期43卷 360-367页

作者： Peng Zhang Stephan V.Roth Peter Muller-Buschbaum Tian-Bai He School of Materials Science and Engineering Key Laboratory for Polymeric Composite and Functional Materials of Ministry of EducationInstitute of Green Chemistry and Molecular EngineeringSun Yat-sen UniversityGuangzhou510275China Deutsches Elektronen-Synchrotron(DESY) Notkestrasse 8522607HamburgGermany Department of Fibre and Polymer Technology KTH Royal Institute of TechnologyTeknikringen 56-58StockholmSE-10044Sweden TUM School of Natural Sciences Department of PhysicsChair for Functional MaterialsTechnical University of MunichJames-Franck-Str.1Garching85748Germany Heinz Maier-Leibnitz-Zentrum(MLZ) Technical University of MunichLichtenbergstr.1Garching85748Germany State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryGraduate University of Chinese Academy of SciencesChinese Academy of SciencesChangchun130022China

The early stages of crystallization and occurrence of surface wrinkling were investigated using poly(butadiene)-block-poly(ε-caprolactone)with an ordered lamellar *** evidence has demonstrated that surface wrinkling precedes nucleation and crystal *** study examined the relationship between surface wrinkling,nucleation,and the formation of crystalline supramolecular structures using atomic force microscopy(AFM)and X-ray scattering *** wrinkling is attributed to curving induced by accumulated stresses,including residual stress from the sample preparation and thermal stress during *** stresses cause large-scale material flow and corresponding changes in the molecular conformations,potentially reducing the nucleation *** hypothesis is supported by the rapid crystal growth observed following the spread of surface ***,the surface curving of the polymer thin film creates local minima of the free energy,facilitating *** nuclei subsequently grow into crystalline supramolecular structures by incorporating polymer molecules from the *** mechanism highlights the role of localized structural inhomogeneity in the early stages of crystallization and provides new insights into structure formation processes.

关键词： Polymer crystallization Nucleation Surface wrinkling Stress Thin film

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Ultrahigh zT from strong electron-phonon interactions and a low-dimensional Fermi surface

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Energy and Environmental Science 2024年第5期17卷 1904-1915页

作者： Ranganayakulu, V.K. Wang, Te-Hsien Chen, Cheng-Lung Huang, Angus Ma, Ma-Hsuan Wu, Chun-Min Tsai, Wei-Han Hung, Tsu-Lien Ou, Min-Nan Jeng, Horng-Tay Lee, Chih-Hao Chen, Kuei-Hsien Li, Wen-Hsien Brod, Madison K. Snyder, G. Jeffrey Chen, Yang-Yuan Institute of Physics Academia Sinica Taipei11529 Taiwan Department of Engineering and System Science National Tsing Hua University Hsinchu30013 Taiwan Taiwan International Graduate Program Taipei11529 Taiwan Department of Physics National Chung Hsing University Taichung City40227 Taiwan Graduate School of Materials Science National Yunlin University of Science and Technology Yunlin64002 Taiwan Bachelor Program in Semiconductor Materials and Fabrication Ming Chi University of Technology New Taipei City243303 Taiwan Department of Physics National Tsing Hua University Hsinchu30013 Taiwan Center for Theory and Computation National Tsing Hua University Hsinchu30013 Taiwan Physics Division National Center for Theoretical Sciences Taipei10617 Taiwan Department of Physics National Central University Jhongli32001 Taiwan National Synchrotron Radiation Research Center Hsinchu Science Park Hsinchu30076 Taiwan Institute of Atomic and Molecular Sciences Academia Sinica Taipei10617 Taiwan Department of Materials Science and Engineering Northwestern University EvanstonIL60208 United States Graduate Institute of Applied Physics National Chengchi University Taipei11605 Taiwan

The outstanding thermoelectric performance of GeTe has attracted significant attention in the research community in recent years. However, many of the underlying physical mechanisms that contribute to GeTe's exceptionally high figure of merit (zT) remain not fully understood. In this study, an Sb-Bi codoped GeTe single crystal (Ge0.86Sb0.08Bi0.06)Te with an ultrahigh zT of 2.7 at 700 K and a record high device zT of 1.41 in the temperature range of 300-773 K was synthesized and investigated. The ultrahigh zT is attributed to the extremely low lattice thermal conductivity induced by strong electron-phonon (EP) interactions as revealed by the experimentally observed Kohn anomaly, through inelastic neutron scattering (INS) measurements. First-principles calculations further demonstrate that the remarkable EP interaction arises from the Fermi surface nesting featured in a one-dimensional (double-walled) topology. Our finding unravels the ultrahigh-zT mechanism in GeTe-based materials, serving as an inspiring guide toward high thermoelectric performance. © 2024 The Royal Society of chemistry.

关键词： Neutron scattering

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Enhanced Light-Matter Interactions for a Single T Center in a Silicon Nanocavity

Enhanced Light-Matter Interactions for a Single T Center in ...

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CLEO: Fundamental Science, CLEO:FS 2024 - Part of Conference on Lasers and Electro-Optics, CLEO 2024

作者： Wong, Yu-En Johnston, Adam Felix-Rendon, Ulises Chen, Songtao Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Smalley-Curl Institute Rice University HoustonTX77005 United States

We investigate light-matter interactions for a single T center coupled to a silicon photonic crystal cavity. By solving Lindblad master equation, we extract the cavity-QED parameters for the coupled system. © Opt... 详细信息

ISBN: (纸本)9781957171395

关键词： Silicon photonics

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Purcell Enhancement of a Single T Center Coupled to a Silicon Nanophotonic Cavity

Purcell Enhancement of a Single T Center Coupled to a Silico...

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CLEO: Fundamental Science, CLEO:FS 2024 - Part of Conference on Lasers and Electro-Optics, CLEO 2024

作者： Felix-Rendon, Ulises Johnston, Adam Wong, Yu-En Chen, Songtao Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Smalley-Curl Institute Rice University HoustonTX77005 United States

We demonstrate Purcell enhancement of a single T center integrated in a silicon photonic crystal cavity, increasing the fluorescence decay rate by a factor of 6.89 and achieving a photon outcoupling rate of 73.3 kHz. ... 详细信息

ISBN: (纸本)9781957171395

关键词： Silicon photonics

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