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arXiv 2024年

作者： Shao, Sen Chiu, Wei-Chi Hossain, Md Shafayat Hou, Tao Wang, Naizhou Belopolski, Ilya Zhao, Yilin Ni, Jinyang Zhang, Qi Li, Yongkai Liu, Jinjin Yahyavi, Mohammad Jin, Yuanjun Feng, Qiange Cui, Peiyuan Zhang, Cheng-Long Yao, Yugui Wang, Zhiwei Yin, Jia-Xin Xu, Su-Yang Ma, Qiong Gao, Wei-Bo Bansil, Arun Hasan, M. Zahid Chang, Guoqing Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore637371 Singapore Department of Physics Northeastern University BostonMA02115 United States Quantum Materials and Sensing Institute Northeastern University BurlingtonMA01803 United States Department of Physics Princeton University PrincetonNJ08544 United States Wako Saitama351-0198 Japan School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems Beijing Institute of Technology Beijing100081 China Material Science Center Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing314011 China Department of Physics Southern University of Science and Technology Shenzhen Guangdong518055 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China Department of Chemistry and Chemical Biology Harvard University CambridgeMA United States Department of Physics Boston College Chestnut HillMA United States CIFAR Azrieli Global Scholars program CIFAR Toronto Canada

Implementing and tuning chirality is fundamental in physics, chemistry, and material science. Chiral charge density waves (CDWs), where chirality arises from correlated charge orders, are attracting intense interest due to their exotic transport and optical properties. However, a general framework for predicting chiral CDW materials is lacking, primarily because the underlying mechanisms remain elusive. Here, we address this challenge by developing the first comprehensive predictive framework, systematically identifying chiral CDWmaterials via first-principles calculations. The key lies in the previously overlooked phase difference of the CDW Q-vectors between layers, which is linked to opposite collective atomic displacements across different layers. This phase difference induces a spiral arrangement of the Q-vectors, ultimately giving rise to a chiral structure in real space. We validate our framework by applying it to the kagome lattice AV3Sb5 (A = K, Rb, Cs), successfully predicting emergent structural chirality. To demonstrate the generality of our approach, we extend it to predict chiral CDWs in the triangular-lattice NbSe2. Beyond material predictions, our theory uncovers a universal and unprecedented Hall effect in chiral CDW materials, occurring without external magnetic fields or intrinsic magnetization. Our experiments on CsV3Sb5 confirm this prediction, observing a unique signature where the Hall conductivity's sign reverses when the input current is reversed, a phenomenon distinct from known Hall effects. Our findings elucidate the mechanisms behind chiral CDWs and open new avenues for discovering materials with unconventional quantum properties, with potential applications in next-generation electronic and spintronic devices. © 2024, CC BY.

关键词： Optical properties

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Observing the steady-state visual evoked potentials with a compact quad-channel spin exchange relaxation-free magnetometer

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Chinese Physics B 2019年第4期28卷 141-144页

作者： Peng-Cheng Du Jian-Jun Li Si-Jia Yang Xu-Tong Wang Yan Zhuo Fan Wang Ru-Quan Wang Institute of Physics Chinese Academy of Sciences School of Physical Sciences University of Chinese Academy of Sciences State Key Laboratory of Brain and Cognitive Science Institute of BiophysicsChinese Academy of Sciences (CAS) CAS Center for Excellence in Brain Science and Intelligence Technology University of Chinese Academy of Sciences Sino-Danish College University of Chinese Academy of Sciences

We observed the steady-state visually evoked potential(SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free(SERF) optically pumped magnetometer(OPM). To this end, 30 s of data were collected, and SSVEP-related magnetic responses with signal intensity ranging from 150 fT to 300 f T were observed for all four channels. The corresponding signal to noise ratio(SNR) was in the range of 3.5–5.5. We then used different channels to operate the sensor as a gradiometer. In the specific case of detecting SSVEP, we noticed that the short channel separation distance led to a strongly diminished gradiometer signal. Although not optimal for the case of SSVEP detection, this set-up can prove to be highly useful for other magnetoencephalography(MEG) paradigms that require good noise *** its compactness, low cost, and good performance, the K-SERF sensor has great potential for biomagnetic field measurements and brain-computer interfaces(BCI).

关键词： optically pumped magnetometers steady-state visually evoked potentials magnetoencephalography

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A Comprehensive Study on the Degradation Process of Medical-Grade Polydioxanone at Low pH

SSRN

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SSRN 2024年

作者： Lelkes, Krisztina Dodzi Jezbera, Daniel Svoboda, Roman Podzimek, Štěpán Loskot, Jan Nalezinková, Martina Voda, Petr Duda, Piotr Fučíková, Alena Myslivcová Hosszú, Tomáš Alferi, Dino Bezrouk, Aleš Department of Medical Biophysics Faculty of Medicine in Hradec Králové Charles University Hradec Králové500 03 Czech Republic Department of Physics Faculty of Science University of Hradec Králové Rokitanského 62 Hradec Králové500 03 Czech Republic Department of Physical Chemistry Faculty of Chemical Technology University of Pardubice Studentská 573 Pardubice532 10 Czech Republic Institute of Chemistry and Technology of Macromolecular Materials Faculty of Chemical Technology University of Pardubice Studentská 573 Pardubice532 10 Czech Republic Department of Biology Faculty of Science University of Hradec Králové Rokitanského 62 Hradec Králové500 03 Czech Republic Institute of Biomedical Engineering University of Silesia in Katowice Będzińska 39 Sosnowiec41-205 Poland Department of Neurosurgery University Hospital Hradec Králové Sokolská 581 Hradec Králové500 05 Czech Republic

Polydioxanone (PPDX) has gained significant attention as a biocompatible and absorbable polymer used in various medical applications, such as sutures and tissue scaffolds. This research presents a thorough investigation into the degradation mechanisms of medical-grade polydioxanone under low pH conditions, simulating physiological environments where the polymer may encounter acidic surroundings during its intended applications, e.g., esophagus and stomach surgery. It mainly focuses on the dependence of the PPDX degradation rate on various pH values (1.0, 1.2, 1.67, 3.78, 7.0, and 7.4) of the test environment, which is a substantial knowledge for successful gastrointestinal treatment. The PPDX suture samples were degraded in the test environments for up to 6 weeks and analyzed using size exclusion chromatography, differential scanning calorimetry, Raman spectroscopy, scanning electron microscopy, X-ray microtomography, and mechanical property measurements. The results show that the PPDX degradation is significantly accelerated at pH below 1.67. Correlations of the molecular weight, crystallinity, glass transition temperature, Young’s modulus, shear modulus, tensile strength, and the 1733 cm−1 Raman peak shoulder area indicate that the degradation mechanism does not change with increasing acidity. Molecular weight, crystallinity, and Young’s modulus are shown to be the most suitable parameters for characterizing general PPDX polymer degradation. On the other hand, measurements of tensile strength, shear modulus, and the 1733 cm−1 Raman peak shoulder area were found to be the most suitable parameters for characterizing the PPDX filament’s macroscopic integrity. Raman spectroscopy is of particular interest in this regard due to its rapidity and practically no requirements on the sample preparation or form. © 2024, The Authors. All rights reserved.

关键词： Differential scanning calorimetry

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Segmental Lennard-Jones interactions for semi-flexible polymer networks

arXiv

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arXiv 2021年

作者： Floyd, Carlos Chandresekaran, Aravind Ni, Haoran Ni, Qin Papoian, Garegin A. Biophysics Program University of Maryland College ParkMD20742 United States Department of Chemistry and Biochemistry University of Maryland College ParkMD20742 United States Department of Chemical and Biomolecular Engineering University of Maryland College ParkMD20742 United States Institute for Physical Science and Technology University of Maryland College ParkMD20742 United States

Simulating soft matter systems such as the cytoskeleton can enable deep understanding of experimentally observed phenomena. One challenge of modeling such systems is realistic description of the steric repulsion between nearby polymers. Previous models of the polymeric excluded volume interaction have the deficit of being non-analytic, being computationally expensive, or allowing polymers to erroneously cross each other. A recent solution to these issues, implemented in the MEDYAN simulation platform, uses analytical expressions obtained from integrating an interaction kernel along the lengths of two polymer segments to describe their repulsion. Here, we extend this model by re-deriving it for lower-dimensional geometrical configurations, deriving similar expressions using a steeper interaction kernel, comparing it to other commonly used potentials, and showing how to parameterize these models. We also generalize this new integrated style of potential by introducing a segmental Lennard-Jones potential, which enables modelling both attractive and repulsive interactions in semi-flexible polymer networks. These results can be further generalized to facilitate the development of effective interaction potentials for other finite elements in simulations of soft-matter systems. Copyright © 2021, The Authors. All rights reserved.

关键词： Lennard-Jones potential

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High pressure synthesis and characterization of the pyrochlore Dy2Pt2O7:A new spin ice material

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Chinese Physics B 2020年第4期29卷 116-120页

作者： Qi Cui Yun-Qi Cai Xiang Li Zhi-Ling Dun Pei-Jie Sun Jian-Shi Zhou Hai-Dong Zhou Jin-Guang Cheng Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China Materials Science and Engineering Program Mechanical EngineeringUniversity of Texas at AustinAustinTexas 78712USA Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement of Ministry of Education School of PhysicsBeijing Institute of TechnologyBeijing 100081China Department of Physics and Astronomy University of TennesseeKnoxvilleTN 37996USA School of Physics Georgia Institute of TechnologyAtlantaGA 30332USA Songshan Lake Materials Laboratory Dongguan 523808China

The cubic pyrochlore Dy2Pt2O7 was synthesized under 4 GPa and 1000℃ and its magnetic and thermodynamic properties were characterized by DC and AC magnetic susceptibility and specific heat down to 0.1 *** found that Dy2Pt2O7 does not form long-range magnetic order,but displays characteristics of canonical spin ice such as Dy2Pt2O7,including(1)a large effective moment 9.64μB close to the theoretical value and a small positive Curie-Weiss temperatureθCW=+0.77 K signaling a dominant ferromagnetic interaction among the Ising spins;(2)a saturation moment ~4.5μB being half of the total moment due to the local<111>Ising anisotropy;(3)thermally activated spin relaxation behaviors in the low(~1 K)and high(~20 K)temperature regions with different energy barriers and characteristic relaxation time;and most importantly,(4)the presence of a residual entropy close to Pauling’s estimation for water ice.

关键词： Dy2Pt2O7 pyrochlore oxide spin ice high-pressure synthesis

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Direct insulator to relativistic quantum Hall transition in graphene

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physical Review B 2023年第20期108卷 205304-205304页

作者： Ching-Chen Yeh Pin-Chi Liao Dinesh K. Patel Wei-Chen Lin Siang-Chi Wang Albert F. Rigosi Randolph E. Elmquist Chi-Te Liang Department of Physics National Taiwan University Taipei 106 Taiwan Physical Measurement Laboratory National Institute of Standards and Technology (NIST) Gaithersburg Maryland 20899 USA Physikalisch-Technische Bundesanstalt (PTB) Bundesallee 100 Braunschweig 38116 Germany Taiwan International Graduate Program Academia Sinica Taipei 115 Taiwan Department of Engineering and System Science National Tsing Hua University Hsinchu 300 Taiwan Center for Quantum Science and Engineering National Taiwan University Taipei 106 Taiwan Taiwan Consortium of Emergent Crystalline Materials (TCECM) Taipei 106 Taiwan

We present evidence of the direct insulator-quantum Hall transition in monolayer epitaxial graphene, a genuine two-dimensional (2D) system. We studied the transition from an insulating state to a quantum Hall state at a high Landau level filling factor ν=6>3 and the plateau-plateau transition from ν=6 to ν=2. Using scaling theory, the critical exponent κ was determined to be 0.41±0.02 for the direct insulator-quantum Hall transition. This closely aligns with κ=0.42±0.02 from the ν=6 to ν=2 quantum Hall plateau-plateau transition. These findings suggest that the two transitions may belong to the same universality class. While similar transitions have been explored in conventional two-dimensional charge systems, our study provides valuable insights into a truly 2D system, deepening our understanding of these transitions.

关键词： Electrical properties Fermions Landau levels Graphene Hall bar Resistivity measurements

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Semiconductor-metal ultrafast laser welding with relocated filaments 21

Semiconductor-metal ultrafast laser welding with relocated f...

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Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI 2021

作者： Chambonneau, Maxime Li, Qingfeng Fedorov, Vladimir Y. Blothe, Markus Tzortzakis, Stelios Nolte, Stefan Institute of Applied Physics Abbe Center of Photonics Friedrich Schiller University Jena Albert-Einstein-Straße 15 Jena07745 Germany Science Program Texas AandM University at Qatar P.O. Box 23874 Doha Qatar P. N. Lebedev Physical Institute of the Russian Academy of Sciences 53 Leninskiy Prospekt Moscow119991 Russia P.O. Box 1527 HeraklionGR-71110 Greece Materials Science and Technology Department University of Crete Heraklion71003 Greece Fraunhofer Institute for Applied Optics and Precision Engineering Iof Center of Excellence in Photonics Albert-Einstein-Straße 7 Jena07745 Germany

ISBN: (数字)9781510641884

ISBN: (纸本)9781510641877

Ultrafast laser welding is a fast, clean, and contactless technique for joining a broad range of materials. Nevertheless, this technique cannot be applied for bonding semiconductors and metals. By investigating the nonlinear propagation of picosecond laser pulses in silicon, it is elucidated how the evolution of filaments during propagation prevents the energy deposition at the semiconductor-metal interface. While the restrictions imposed by nonlinear propagation effects in semiconductors usually inhibit countless applications, the possibility to perform semiconductor-metal ultrafast laser welding is demonstrated. This technique relies on the determination and the precompensation of the nonlinear focal shift for relocating filaments and thus optimizing the energy deposition at the interface between the materials. The resulting welds show remarkable shear joining strengths (up to 2.2 MPa) compatible with applications in microelectronics. Material analyses shed light on the physical mechanisms involved during the interaction. © 2021 SPIE. All rights reserved.

关键词： Ultrafast lasers

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Widely Tunable Berry Curvature in the Magnetic Semimetal Cr1+δTe2

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Advanced Materials 2023年第12期35卷

作者： Fujisawa, Yuita Pardo-Almanza, Markel Hsu, Chia-Hsiu Mohamed, Atwa Yamagami, Kohei Krishnadas, Anjana Chang, Guoqing Chuang, Feng-Chuan Khoo, Khoong Hong Zang, Jiadong Soumyanarayanan, Anjan Okada, Yoshinori Okinawa904-0495 Japan Department of Physics National Sun Yat-sen University Kaohsiung80424 Taiwan Physics Division National Center for Theoretical Sciences Taipei10617 Taiwan Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Center for Theoretical and Computational Physics National Sun Yat-sen University Kaohsiung80424 Taiwan Institute of High Performance Computing Agency for Science Technology and Research Singapore138632 Singapore Department of Physics and Astronomy University of New Hampshire DurhamNH 03824 United States Materials Science Program University of New Hampshire DurhamNH 03824 United States Department of Physics National University of Singapore Singapore117551 Singapore Institute of Materials Research and Engineering Agency for Science Technology and Research Singapore138634 Singapore

Magnetic semimetals have increasingly emerged as lucrative platforms hosting spin-based topological phenomena in real and momentum spaces. Cr1+δTe2 is a self-intercalated magnetic transition metal dichalcogenide (TMD), which exhibits topological magnetism and tunable electron filling. While recent studies have explored real-space Berry curvature effects, similar considerations of momentum-space Berry curvature are lacking. Here, the electronic structure and transport properties of epitaxial Cr1+δTe2 thin films are systematically investigated over a range of doping, δ (0.33 – 0.71). Spectroscopic experiments reveal the presence of a characteristic semi-metallic band region, which shows a rigid like energy shift with δ. Transport experiments show that the intrinsic component of the anomalous Hall effect (AHE) is sizable and undergoes a sign flip across δ. Finally, density functional theory calculations establish a link between the doping evolution of the band structure and AHE: the AHE sign flip is shown to emerge from the sign change of the Berry curvature, as the semi-metallic band region crosses the Fermi energy. These findings underscore the increasing relevance of momentum-space Berry curvature in magnetic TMDs and provide a unique platform for intertwining topological physics in real and momentum spaces. © 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.

关键词： Density functional theory

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Protein Flexibility and Dissociation Pathway Differentiation Can Explain Onset of Resistance Mutations in Kinases**

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Angewandte Chemie 2022年第28期134卷

作者： Mrinal Shekhar Zachary Smith Markus A. Seeliger Pratyush Tiwary Center for Development of Therapeutics Broad Institute of MIT and Harvard Cambridge MA 02142 USA Biophysics Program and Institute for Physical Science and Technology University of Maryland College Park MD 20742 USA Department of Pharmacological Sciences Stony Brook University Stony Brook NY 11794-8651 USA Department of Chemistry and Biochemistry and Institute for Physical Science and Technology University of Maryland College Park MD 20742 USA

Understanding how mutations render a drug ineffective is a problem of immense relevance. Often the mechanism through which mutations cause drug resistance can be explained purely through thermodynamics. However, the more perplexing situation is when two proteins have the same drug binding affinities but different residence times. In this work, we demonstrate how all-atom molecular dynamics simulations using recent developments grounded in statistical mechanics can provide a detailed mechanistic rationale for such variances. We discover dissociation mechanisms for the anti-cancer drug Imatinib (Gleevec) against wild-type and the N368S mutant of Abl kinase. We show how this point mutation triggers far-reaching changes in the protein's flexibility and leads to a different, much faster, drug dissociation pathway. We believe that this work marks an efficient and scalable approach to obtain mechanistic insight into resistance mutations in biomolecular receptors that are hard to explain using a structural perspective.

关键词： Kinase Kinetics Molecular Dynamics Protein Flexibility Resistance Mutations

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NiOx passivation in perovskite solar cells: from surface reactivity to device performance

arXiv

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arXiv 2024年

作者： Mohanraj, John Samanta, Bipasa Almora, Osbel Escalante, Renán Marsal, Lluis F. Jenatsch, Sandra Gadola, Arno Ruhstaller, Beat Anta, Juan A. Toroker, Maytal Caspary Olthof, Selina Department of Chemistry University of Cologne Greinstrasse 4−6 Cologne50939 Germany Department of Materials Science and Engineering Technion–Israel Institute of Technology Haifa3600003 Israel Departament d'Enginyeria Electrònica Elèctrica i Automàtica Universitat Rovira i Virgili Tarragona43007 Spain Department of Physical Chemical and Natural Systems Universidad Pablo de Olavide Sevilla41013 Spain Fluxim AG Katharina-Sulzer-Platz 2 Winterthur8400 Switzerland The Nancy and Stephen Grand Technion Energy Program Haifa3200003 Israel

Non-stoichiometric nickel oxide (NiOx) is the only metal oxide successfully used as hole transport material in p-i-n type perovskite solar cells (PSCs). Its favorable opto-electronic properties and facile large-scale preparation methods are potentially relevant for future commercialization of PSCs, though currently low operational stability of PSCs containing NiOx hole transport layers are reported. Poorly understood degradation reactions at the interface to the perovskite are seen as cause for the inferior stability and a variety of interface passivation approaches have been shown to be effective in improving the overall solar cell performance. To gain a better understanding of the processes happening at this interface, we systematically passivated possible specific defects on NiOx with three different categories of organic/inorganic compounds. The effects on the NiOx and the perovskite (MAPbI3) were investigated using x-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) where we find that the structural stability and film formation can be significantly affected. In combination with Density Functional Theory (DFT) calculations, a likely origin of NiOx-perovskite degradation interactions is proposed. The surface passivated NiOx was incorporated into MAPbI3 based PSCs and its influence on overall performance, particularly operational stability, was investigated by current-voltage (J-V), impedance spectroscopy (IS), and open circuit voltage decay (OCVD) measurements. Interestingly, we find that a superior structural stability due to an interface passivation must not relate to high operational stability. The discrepancy comes from the formation of excess ions at the interface which negatively impacts all solar cell parameters. © 2024, CC BY-NC-SA.

关键词： Nickel oxide

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