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Design of high-temperature superconductors at moderate pressures by alloying AlH3 or GaH3
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作者 Xiaowei Liang Xudong Wei +4 位作者 Eva Zurek Aitor Bergara Peifang Li Guoying Gao Yongjun Tian 《Matter and Radiation at Extremes》 SCIE EI CSCD 2024年第1期94-103,共10页
Since the discovery of hydride superconductors,a significant challenge has been to reduce the pressure required for their stabilization.In this context,we propose that alloying could be an effective strategy to achiev... Since the discovery of hydride superconductors,a significant challenge has been to reduce the pressure required for their stabilization.In this context,we propose that alloying could be an effective strategy to achieve this.We focus on a series of alloyed hydrides with the AMH_(6)composition,which can be made via alloying A15 AH_(3)(A=Al or Ga)with M(M=a group IIIB or IVB metal),and study their behavior under pressure.Seven of them are predicted to maintain the A15-type structure,similar to AH_(3)under pressure,providing a platform for studying the effects of alloying on the stability and superconductivity of AH_(3).Among these,the A15-type phases of AlZrH_(6)and AlHfH_(6)are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa,respectively.Furthermore,they remain dynamically stable at even lower pressures,as low as 13 GPa for AlZrH_(6)and 6 GPa for AlHfH_(6).These pressures are significantly lower than that required for stabilizing A15 AlH3.Additionally,the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3.This enhancement leads to higher critical temperatures(Tc)of 75 and 76 K for AlZrH_(6)and AlHfH_(6)at 20 and 10 GPa,respectively.In the case of GaMH_(6)alloys,where M represents Sc,Ti,Zr,or Hf,these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH_(3) from 160 GPa to 116,95,80,and 85 GPa,respectively.Particularly noteworthy are the A15-type GaMH_(6)alloys,which remain dynamically stable at low pressures of 97,28,5,and 6 GPa,simultaneously exhibiting high Tc of 88,39,70,and 49 K at 100,35,10,and 10 GPa,respectively.Overall,these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures. 展开更多
关键词 ALLOYING ALLOYS SUPERCONDUCTORS
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Pressure-induced evolution of stoichiometries and electronic structures of host-guest Na-B compounds 被引量:1
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作者 Zixuan Guo Xing Li +3 位作者 Aitor Bergara Shicong Ding Xiaohua Zhang Guochun Yang 《Matter and Radiation at Extremes》 SCIE EI CSCD 2023年第6期101-110,共10页
Superionic and electride behaviors in materials,which induce a variety of exotic physical properties of ions and electrons,are of great importance both in fundamental research and for practical applications.However,th... Superionic and electride behaviors in materials,which induce a variety of exotic physical properties of ions and electrons,are of great importance both in fundamental research and for practical applications.However,their coexistence in hot alkali-metal borides has not been observed.In this work,we apply first-principles structure search calculations to identify eight Na-B compounds with host-guest structures,which exhibit a wide range of building blocks and interesting properties linked to the Na/B composition.Among the known borides,Na-rich Na9B stands out as the composition with the highest alkali-metal content,featuring vertex-and face-sharing BNa16 polyhedra.Notably,it exhibits electride characteristics and transforms into a superionic electride at 200 GPa and 2000 K,displaying unusual Na atomic diffusion behavior attributed to the modulation of the interstitial anion electrons.It demonstrates semiconductor behavior in the solid state,and metallic properties associated with Na 3p/3s states in the superionic and liquid regions.On the other hand,B-rich NaB7,consisting of a unique covalent B framework,is predicted to exhibit low-frequency phonon-mediated superconductivity with a T_(c) of 16.8 K at 55 GPa.Our work advances the understanding of the structures and properties of alkali-metal borides. 展开更多
关键词 alkali structures COMPOUNDS
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Electrostatic interactions in twisted bilayer graphene
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作者 Tommaso Cea Pierre A.Pantaleón +1 位作者 Niels R.Walet Francisco Guinea 《Nano Materials Science》 EI CAS CSCD 2022年第1期27-35,共9页
The effects of the long range electrostatic interaction in twisted bilayer graphene are described using the HartreeFock approximation. The results show a significant dependence of the band widths and shapes on electro... The effects of the long range electrostatic interaction in twisted bilayer graphene are described using the HartreeFock approximation. The results show a significant dependence of the band widths and shapes on electron filling,and the existence of broken symmetry phases at many densities, either valley/spin polarized, with broken sublattice symmetry, or both. 展开更多
关键词 GRAPHENE TWISTED INTERACTIONS
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Silicon Nanocrystals on the Surface of Standard Si Wafers: A Micro-Raman Investigation
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作者 Mohammed S. G. Mohammed Enzo Cazzanelli +1 位作者 Angela Fasanella Marco Castriota 《Journal of Materials Science and Chemical Engineering》 2018年第7期104-116,共13页
The presence of silicon nanocrystals on the surface of standard wafer samples of Si, conserved under “usual” laboratory conditions, has been investigated by micro-Raman analysis, performed for increasing intensity o... The presence of silicon nanocrystals on the surface of standard wafer samples of Si, conserved under “usual” laboratory conditions, has been investigated by micro-Raman analysis, performed for increasing intensity of laser irradiation. The poor thermal connection of such small crystals to the Si wafer bulk allows for the appearance of two well distinct Raman bands in the spectra, with a different evolution for increasing irradiance levels: the first, expected, due to bulk silicon response, the other one assignable to the silicon nanocrystals. A careful analysis of peak position and linewidth has been carried out, both for the Raman contribution from the nanocrystals, reaching high temperatures under irradiation (up to 1400 K), and for the one from the “bulk” Si, which remains practically at room temperature. The analysis of the spectra and the comparison with previous studies on nc-Si suggest that such nanocrystals do not have a very small size, so that the observed changes of spectral parameters are mainly due to laser heating, rather than quantum confinement effects. In any case, we performed also an independent size deter-mination by AFM mapping, confirming a size distribution well peaked be-tween 50 and 100 nm. As a corollary from this analysis, we get the indication that apparent linewidths and positions, at low laser irradiation levels, can be slightly changed in the presence of nc-Si on the surface. It is due to the differ-ent thermal responses of bulk and nanocrystalline components, inducing un-resolved separate components;this hypothesis suggests reanalysing some previous experimental data, in particular for many Raman spectra of Si col-lected at “room temperature”. 展开更多
关键词 Silicon NANOCRYSTALS Laser Heating RAMAN LINEWIDTH AFM Measurement
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Exploring van der Waals materials with high anisotropy:geometrical and optical approaches
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作者 Aleksandr S.Slavich Georgy A.Ermolaev +16 位作者 Mikhail K.Tatmyshevskiy Adilet N.Toksumakov Olga G.Matveeva Dmitriy V.Grudinin Kirill V.Voronin Arslan Mazitov Konstantin V.Kravtsov Alexander V.Syuy Dmitry M.Tsymbarenko Mikhail S.Mironov Sergey M.Novikov Ivan Kruglov Davit A.Ghazaryan Andrey A.Vyshnevyy Aleksey V.Arsenin Valentyn S.Volkov Kostya S.Novoselov 《Light(Science & Applications)》 SCIE EI CSCD 2024年第4期645-653,共9页
The emergence of van der Waals(vdW)materials resulted in the discovery of their high optical,mechanical,and electronic anisotropic properties,immediately enabling countless novel phenomena and applications.Such succes... The emergence of van der Waals(vdW)materials resulted in the discovery of their high optical,mechanical,and electronic anisotropic properties,immediately enabling countless novel phenomena and applications.Such success inspired an intensive search for the highest possible anisotropic properties among vdW materials.Furthermore,the identification of the most promising among the huge family of vdW materials is a challenging quest requiring innovative approaches.Here,we suggest an easy-to-use method for such a survey based on the crystallographic geometrical perspective of vdW materials followed by their optical characterization.Using our approach,we found As2S3 as a highly anisotropic vdW material.It demonstrates high in-plane optical anisotropy that is~20%larger than for rutile and over two times as large as calcite,high refractive index,and transparency in the visible range,overcoming the century-long record set by rutile.Given these benefits,As2S3 opens a pathway towards nextgeneration nanophotonics as demonstrated by an ultrathin true zero-order quarter-wave plate that combines classical and the Fabry–Pérot optical phase accumulations.Hence,our approach provides an effective and easy-to-use method to find vdW materials with the utmost anisotropic properties. 展开更多
关键词 ANISOTROPY ANISOTROPIC HIGH
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Efficient passivation of DY center in CH_(3)NH_(3)PbBr_(3) by chlorine:Quantum molecular dynamics
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作者 Ran Shi Wei-Hai Fang +2 位作者 Andrey S.Vasenko Run Long Oleg V.Prezhdo 《Nano Research》 SCIE EI CSCD 2022年第3期2112-2122,共11页
MAPbBr_(3)(MA=CH_(3)NH_(3)^(+))doping with bismuth increases electric conductivity,charge carrier density and photostability,reduces toxicity,and expands light absorption.However,Bi doping shortens excited-state lifet... MAPbBr_(3)(MA=CH_(3)NH_(3)^(+))doping with bismuth increases electric conductivity,charge carrier density and photostability,reduces toxicity,and expands light absorption.However,Bi doping shortens excited-state lifetimes due to formation of DY−charge recombination centers.Using nonadiabatic molecular dynamics and time-domain density functional theory,we demonstrate that the DY−center forms a deep,highly localized hole trap,which accelerates nonradiative relaxation ten-fold and is responsible for 90%of carrier losses.Hole trapping occurs by coupling between the valence band and the trap state,facilitated by the Br atoms surrounding the Bi dopant.Passivation of the DY−center with chlorines heals the local geometry distortion,eliminates the trap state,and makes the carrier lifetimes longer than even in pristine MAPbBr_(3).The decreased charge recombination arises from reduced nonadiabatic coupling and shortened coherence time,due to diminished electron–hole overlap around the passivated defect.Our study demonstrates accelerated nonradiative recombination in Bi-doped MAPbBr_(3),suggests a strategy for defect passivation and reduction of nonradiative energy losses,and provides atomistic insights into unusual defect properties of metal halide perovskites needed for rational design of high-performance perovskite solar cells and optoelectronic devices. 展开更多
关键词 Hybrid organic-inorganic perovskite DY−center and Cl passivation charge trapping and recombination nonadiabatic molecular dynamics time-domain density functional theory.
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Large anomalous Hall, Nernst effect and topological phases in the 3d-4d/5d-based oxide double perovskites
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作者 Kartik Samanta Jonathan Noky +3 位作者 Iñigo Robredo Juergen Kuebler Maia G.Vergniory Claudia Felser 《npj Computational Materials》 SCIE EI CSCD 2023年第1期613-622,共10页
Magnetism and spin-orbit coupling are two fundamental and interconnected properties of oxide materials,that can give rise to various topological transport phenomena,including anomalous Hall and anomalous Nernst effect... Magnetism and spin-orbit coupling are two fundamental and interconnected properties of oxide materials,that can give rise to various topological transport phenomena,including anomalous Hall and anomalous Nernst effects.These transport responses can be significantly enhanced by designing an electronic structure with a large Berry curvature.In this context,rocksalt-ordered double perovskites(DP),denoted as A2BB’O6,with two distinct transition metal sites are very powerful platforms for exploration and research.In this work,we present a comprehensive study based on the intrinsic anomalous transport in cubic and tetragonal stable DP compounds with 3d-4d/5d elements.Our findings reveal that certain DP compounds show a large anomalous Hall effect,displaying topological band crossings in the proximity of the Fermi energy. 展开更多
关键词 TOPOLOGICAL PEROVSKITE Nernst
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A plasmonic route for the integrated wireless communication of subdiffraction-limited signals 被引量:11
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作者 Hao Chi Zhang Le Peng Zhang +4 位作者 Pei Hang He Jie Xu Cheng Qian Francisco J.Garcia-Vidal Tie Jun Cui 《Light(Science & Applications)》 SCIE EI CAS CSCD 2020年第1期930-938,共9页
Perfect lenses,superlenses and time-reversal mirrors can support and spatially separate evanescent waves,which is the basis for detecting subwavelength information in the far field.However,the inherent limitations of ... Perfect lenses,superlenses and time-reversal mirrors can support and spatially separate evanescent waves,which is the basis for detecting subwavelength information in the far field.However,the inherent limitations of these methods have prevented the development of systems to dynamically distinguish subdiffraction-limited signals.Utilizing the physical merits of spoof surface plasmon polaritons(SPPs),we demonstrate that subdiffraction-limited signals can be transmitted on planar integrated SPP channels with low loss,low channel interference,and high gain and can be radiated with a very low environmental sensitivity.Furthermore,we show how deep subdiffraction-limited signals that are spatially coupled can be distinguished after line-of-sight wireless transmission.For a visualized demonstration,we realize the high-quality wireless communication of two movies on subwavelength channels over the line of sight in real time using our plasmonic scheme,showing significant advantages over the conventional methods. 展开更多
关键词 COMMUNICATION spatially DIFFRACTION
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Chirality-assisted lateral momentum transfer for bidirectional enantioselective separation 被引量:11
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作者 Yuzhi Shi Tongtong Zhu +7 位作者 Tianhang Zhang Alfredo Mazzulla Din Ping Tsai Weiqiang Ding Ai Qun Liu Gabriella Cipparrone Juan Jose Saenz Cheng-Wei Qiu 《Light(Science & Applications)》 SCIE EI CAS CSCD 2020年第1期1418-1429,共12页
Lateral optical forces induced by linearly polarized laser beams have been predicted to deflect dipolar particles with opposite chiralities toward opposite transversal directions.These“chirality-dependent”forces can... Lateral optical forces induced by linearly polarized laser beams have been predicted to deflect dipolar particles with opposite chiralities toward opposite transversal directions.These“chirality-dependent”forces can offer new possibilities for passive all-optical enantioselective sorting of chiral particles,which is essential to the nanoscience and drug industries.However,previous chiral sorting experiments focused on large particles with diameters in the geometrical-optics regime.Here,we demonstrate,for the first time,the robust sorting of Mie(size~wavelength)chiral particles with different handedness at an air–water interface using optical lateral forces induced by a single linearly polarized laser beam.The nontrivial physical interactions underlying these chirality-dependent forces distinctly differ from those predicted for dipolar or geometrical-optics particles.The lateral forces emerge from a complex interplay between the light polarization,lateral momentum enhancement,and out-of-plane light refraction at the particle-water interface.The sign of the lateral force could be reversed by changing the particle size,incident angle,and polarization of the obliquely incident light. 展开更多
关键词 MOMENTUM CHIRAL OPTICS
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Hybrid photonic-plasmonic cavities based on the nanoparticle-on-a-mirror configuration 被引量:3
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作者 ANGELA I.BARREDA MARIO ZAPATA-HERRERA +4 位作者 ISABELLE M.PALSTRA LAURA MERCADÉ JAVIER AIZPURUA A.FEMIUS KOENDERINK ALEJANDRO MARTÍNEZ 《Photonics Research》 SCIE EI CAS CSCD 2021年第12期2398-2419,共22页
Hybrid photonic-plasmonic cavities have emerged as a new platform to increase light-matter interaction capable to enhance the Purcell factor in a singular way not attainable with either photonic or plasmonic cavities ... Hybrid photonic-plasmonic cavities have emerged as a new platform to increase light-matter interaction capable to enhance the Purcell factor in a singular way not attainable with either photonic or plasmonic cavities separately.In the hybrid cavities proposed so far,the plasmonic element is usually a metallic bow-tie antenna,so the plasmonic gap—defined by lithography-is limited to minimum values of several nanometers.Nanoparticle-on-a-mirror(NPoM)cavities are far superior to achieve the smallest possible mode volumes,as plasmonic gaps smaller than 1 nm can be created.Here,we design a hybrid cavity that combines an NPoM plasmonic cavity and a dielectric-nanobeam photonic crystal cavity operating at transverse-magnetic polarization.The metallic nanoparticle can be placed very close(<1 nm)to the upper surface of the dielectric cavity,which acts as a low-reflectivity mirror.We demonstrate through numerical calculations of the local density of states that this hybrid plasmonic-photonic cavity exhibits quality factors𝑄above 10^(3) and normalized mode volumes𝑉down to 10^(−3),thus resulting in high Purcell factors(F_(P)≈10^(5)),while being experimentally feasible with current technology.Our results suggest that hybrid cavities with sub-nanometer gaps should open new avenues for boosting light-matter interaction in nanophotonic systems. 展开更多
关键词 MIRROR CAVITY NANOPARTICLE
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Design of active and stable catalysts by embedding nitrogen-doped carbon oxygen reduction reaction CoxOy nanoparticles into 被引量:1
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作者 Fan Yang Mikel Abadia +6 位作者 Chaoqiu Chen Weike Wang Le Li Lianbing Zhang Celia Rogero Andrey Chuvilin Mato Knez 《Nano Research》 SCIE EI CAS CSCD 2017年第1期97-107,共11页
The oxygen reduction reaction (ORR) is essential in research pertaining to life science and energy. In applications, platinum-based catalysts give ideal reactivity, but, in practice, are often subject to high costs ... The oxygen reduction reaction (ORR) is essential in research pertaining to life science and energy. In applications, platinum-based catalysts give ideal reactivity, but, in practice, are often subject to high costs and poor stability. Some costefficient transition metal oxides have exhibited excellent ORR reactivity, but the stability and durability of such alternative catalyst materials pose serious challenges. Here, we present a facile method to fabricate uniform CoxOy nanoparticles and embed them into N-doped carbon, which results in a composite of extraordinary stability and durability, while maintaining its high reactivity. The half-wave potential shows a negative shift of only 21 mV after 10,000 cycles, only one third of that observed for Pt/C (63 mV). Furthermore, after 100,000 s testing at a constant potential, the current decreases by only 17%, significantly less than for Pt/C (35%). The exceptional stability and durability results from the system architecture, which comprises a thin carbon shell that prevents agglomeration of the CoxOy nanoparticles and their detaching from the substrate. 展开更多
关键词 atomic layer deposition cobalt oxide POLYDOPAMINE oxygen reduction reaction
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Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma 被引量:1
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作者 G.Cristoforetti L.Antonelli +26 位作者 D.Mancelli S.Atzeni F.Baffigi F.Barbato D.Batani G.Boutoux F.D'Amato J.Dostal R.Dudzak E.Filippov Y.J.Gu L.Juha O.Klimo M.Krus S.Malko A.S.Martynenko Ph.Nicolai V.Ospina S.Pikuz O.Renner J.Santos V.T.Tikhonchuk J.Trela S.Viciani L.Volpe S.Weber L.A.Gizzi 《High Power Laser Science and Engineering》 SCIE CAS CSCD 2019年第3期142-155,共14页
Laser–plasma interaction(LPI)at intensities 1015–1016 W·cm^-2 is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes o... Laser–plasma interaction(LPI)at intensities 1015–1016 W·cm^-2 is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons.Such a regime is of paramount importance for inertial confinement fusion(ICF)and in particular for the shock ignition scheme.In this paper we report on an experiment carried out at the Prague Asterix Laser System(PALS)facility to investigate the extent and time history of stimulated Raman scattering(SRS)and two-plasmon decay(TPD)instabilities,driven by the interaction of an infrared laser pulse at an intensity^1.2×1016 W·cm^-2 with a^100μm scalelength plasma produced from irradiation of a flat plastic target.The laser pulse duration(300 ps)and the high value of plasma temperature(~4 ke V)expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions.Experimental results show that absolute TPD/SRS,driven at a quarter of the critical density,and convective SRS,driven at lower plasma densities,are well separated in time,with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse.Side-scattering SRS,driven at low plasma densities,is also clearly observed.Experimental results are compared to fully kinetic large-scale,two-dimensional simulations.Particle-in-cell results,beyond reproducing the framework delineated by the experimental measurements,reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance. 展开更多
关键词 plasma simulations shock IGNITION stimulated RAMAN scattering two-plasmon DECAY
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Indentation fracture toughness of single-crystal Bi2Te3 topological insulators 被引量:1
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作者 Caterina Lamuta Anna Cupolillo +4 位作者 Antonio Politano Ziya S. Aliev Mahammad B. Babanly Evgueni V. Chulkov Leonardo Pagnotta 《Nano Research》 SCIE EI CAS CSCD 2016年第4期1032-1042,共11页
Bismuth teUuride (Bi2Te3) is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their ap... Bismuth teUuride (Bi2Te3) is one of the most important commercial thermoelectric materials. In recent years, the discovery of topologically protected surface states in Bi chalcogenides has paved the way for their application in nanoelectronics. Determination of the fracture toughness plays a crucial role for the potential application of topological insulators in flexible electronics and nanoelectro- mechanical devices. Using depth-sensing nanoindentation tests, we investigated for the first time the fracture toughness of bulk single crystals of Bi2Te3 topological insulators, grown using the Bridgmantockbarger method. Our results highlight one of the possible pitfalls of the technology based on topological insulators. 展开更多
关键词 topological insulators bismuth telluride (Bi2Te3) fracture toughness NANOINDENTATION
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Reflecting laser-driven shocks in diamond in the megabar pressure range 被引量:1
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作者 K.Jakubowska D.Mancelli +12 位作者 R.Benocci J.Trela I.Errea A.S.Martynenko P.Neumayer O.Rosmej B.Borm A.Molineri C.Verona D.Cannatà A.Aliverdiev H.E.Roman D.Batani 《High Power Laser Science and Engineering》 SCIE CAS CSCD 2021年第1期29-41,共13页
In this work we present experimental results on the behavior of diamond at megabar pressure. The experiment was performed using the PHELIX facility at GSI in Germany to launch a planar shock into solid multi-layered d... In this work we present experimental results on the behavior of diamond at megabar pressure. The experiment was performed using the PHELIX facility at GSI in Germany to launch a planar shock into solid multi-layered diamond samples. The target design allows shock velocity in diamond and in two metal layers to be measured as well as the free surface velocity after shock breakout. As diagnostics, we used two velocity interferometry systems for any reflector(VISARs). Our measurements show that for the pressures obtained in diamond(between 3 and 9 Mbar),the propagation of the shock induces a reflecting state of the material. Finally, the experimental results are compared with hydrodynamical simulations in which we used different equations of state, showing compatibility with dedicated SESAME tables for diamond. 展开更多
关键词 carbon dynamic compression equation of state shock wave VISAR
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Novel superhard boron-rich nitrides under pressure
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作者 Linyan Wang Rongxin Sun +10 位作者 Wenhui Liu Zhikang Yuan Aitor Bergara Xiaowei Liang Shuai Chen Xiang-Feng Zhou Bo Xu Julong He Dongli Yu Guoying Gao Yongjun Tian 《Science China Materials》 SCIE EI CSCD 2020年第11期2358-2364,共7页
Boron and its compounds have attracted much attention due to their interesting and complex structures[1-4].In particular,boron-rich compounds containing icosahedral structures have excellent properties,such as low den... Boron and its compounds have attracted much attention due to their interesting and complex structures[1-4].In particular,boron-rich compounds containing icosahedral structures have excellent properties,such as low density,high hardness,high melting point and low wear coffi-cient. 展开更多
关键词 超硬材料 机械稳定性 动力学稳定性 粒子群优化算法 热力学稳定 硼化合物 氮化物 二十面体
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Boron nitride nanoresonators for phonon-enhanced molecular vibrational spectroscopy at the strong coupling limit
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作者 Marta Autore Peining Li +10 位作者 Irene Dolado Francisco J Alfaro-Mozaz Ruben Esteban Ainhoa Atxabal Fèlix Casanova Luis E Hueso Pablo Alonso-González Javier Aizpurua Alexey Y Nikitin Saül Vélez Rainer Hillenbrand 《Light(Science & Applications)》 SCIE EI CAS CSCD 2017年第1期55-62,共8页
Enhanced light-matter interactions are the basis of surface-enhanced infrared absorption(SEIRA)spectroscopy,and conventionally rely on plasmonic materials and their capability to focus light to nanoscale spot sizes.Ph... Enhanced light-matter interactions are the basis of surface-enhanced infrared absorption(SEIRA)spectroscopy,and conventionally rely on plasmonic materials and their capability to focus light to nanoscale spot sizes.Phonon polariton nanoresonators made of polar crystals could represent an interesting alternative,since they exhibit large quality factors,which go far beyond those of their plasmonic counterparts.The recent emergence of van der Waals crystals enables the fabrication of highquality nanophotonic resonators based on phonon polaritons,as reported for the prototypical infrared-phononic material hexagonal boron nitride(h-BN).In this work we use,for the first time,phonon-polariton-resonant h-BN ribbons for SEIRA spectroscopy of small amounts of organic molecules in Fourier transform infrared spectroscopy.Strikingly,the interaction between phonon polaritons and molecular vibrations reaches experimentally the onset of the strong coupling regime,while numerical simulations predict that vibrational strong coupling can be fully achieved.Phonon polariton nanoresonators thus could become a viable platform for sensing,local control of chemical reactivity and infrared quantum cavity optics experiments. 展开更多
关键词 boron nitride phonon polaritons strong coupling surface-enhanced infrared absorption spectroscopy SEIRA
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Ultrafast laser-driven topological spin textures on a 2D magnet
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作者 Mara Strungaru Mathias Augustin Elton J.G.Santos 《npj Computational Materials》 SCIE EI CSCD 2022年第1期1630-1635,共6页
Ultrafast laser excitations provide an efficient and low-power consumption alternative since different magnetic properties and topological spin states can be triggered and manipulated at the femtosecond(fs)regime.Howe... Ultrafast laser excitations provide an efficient and low-power consumption alternative since different magnetic properties and topological spin states can be triggered and manipulated at the femtosecond(fs)regime.However,it is largely unknown whether laser excitations already used in data information platforms can manipulate the magnetic properties of recently discovered two-dimensional(2D)van der Waals(vdW)materials.Here we show that ultrashort laser pulses(30−85 fs)can not only manipulate magnetic domains of 2D-XY CrCl_(3)ferromagnets,but also induce the formation and control of topological nontrivial meron and antimeron spin textures.We observed that these spin quasiparticles are created within~100 ps after the excitation displaying rich dynamics through motion,collision and annihilation with emission of spin waves throughout the surface.Our findings highlight substantial opportunities of using photonic driving forces for the exploration of spin textures on 2D magnetic materials towards magneto-optical topological applications. 展开更多
关键词 laser EXCITATION TOPOLOGICAL
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An atomistic approach for the structural and electronic properties of twisted bilayer graphene-boron nitride heterostructures
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作者 Min Long Pierre A.Pantaleón +3 位作者 Zhen Zhan Francisco Guinea JoseÁngel Silva-Guillén Shengjun Yuan 《npj Computational Materials》 SCIE EI CSCD 2022年第1期687-696,共10页
Twisted bilayer graphene(TBG)has taken the spotlight in the condensed matter community since the discovery of correlated phases.In this work,we study heterostructures of TBG and hexagonal boron nitride(hBN)using an at... Twisted bilayer graphene(TBG)has taken the spotlight in the condensed matter community since the discovery of correlated phases.In this work,we study heterostructures of TBG and hexagonal boron nitride(hBN)using an atomistic tight-binding model together with semi-classical molecular dynamics to consider relaxation effects.The hBN substrate has significant effects on the band structure of TBG even in the case where TBG and hBN are not aligned.Specifically,the substrate induces a large mass gap and strong pseudo-magnetic fields that break the layer degeneracy.Interestingly,such degeneracy can be recovered with a second hBN layer.Finally,we develop a continuum model that describes the tight-binding band structure.Our results show that a real-space tight-binding model in combination with semi-classical molecular dynamics is a powerful tool to study the electronic properties of moiréheterostructures,and to explain experimental results in which the effect of the substrate plays an important role. 展开更多
关键词 BORON ELECTRONIC TWISTED
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Glide symmetry protected higher-order topological insulators from semimetals with butterfly-like nodal lines
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作者 Xiaoting Zhou Chuang-Han Hsu +5 位作者 Cheng-Yi Huang Mikel Iraola Juan L.Mañes Maia G.Vergniory Hsin Lin Nicholas Kioussis 《npj Computational Materials》 SCIE EI CSCD 2021年第1期1871-1876,共6页
Most topological insulators(TIs)discovered today in spinful systems can be transformed from topological semimetals(TSMs)with vanishing bulk gap via introducing the spin-orbit coupling(SOC),which manifests the intrinsi... Most topological insulators(TIs)discovered today in spinful systems can be transformed from topological semimetals(TSMs)with vanishing bulk gap via introducing the spin-orbit coupling(SOC),which manifests the intrinsic links between the gapped topological insulator phases and the gapless TSMs.Recently,we have discovered a family of TSMs in time-reversal invariant spinless systems,which host butterfly-like nodal-lines(NLs)consisting of a pair of identical concentric intersecting coplanar ellipses(CICE).In this Communication,we unveil the intrinsic link between this exotic class of nodal-line semimetals(NLSMs)and a Z_(4)=2 topological crystalline insulator(TCI),by including substantial SOC.We demonstrate that in three space groups(i.e.,Pbam(No.55),P4/mbm(No.127),and P4_(2)/mbc(No.135)),the TCI supports a fourfold Dirac fermion on the(001)surface protected by two glide symmetries,which originates from the intertwined drumhead surface states of the CICE NLs.The higher order topology is further demonstrated by the emergence of one-dimensional helical hinge states,indicating the discovery of a higher order topological insulator protected by a glide symmetry. 展开更多
关键词 topological protected INSULATOR
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Orbital magneto-optical response of periodic insulators from first principles
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作者 Irina V.Lebedeva David A.Strubbe +1 位作者 Ilya V.Tokatly Angel Rubio 《npj Computational Materials》 SCIE EI CSCD 2019年第1期874-882,共9页
Magneto-optical response,i.e.optical response in the presence of a magnetic field,is commonly used for characterization of materials and in optical communications.However,quantum mechanical description of electric and... Magneto-optical response,i.e.optical response in the presence of a magnetic field,is commonly used for characterization of materials and in optical communications.However,quantum mechanical description of electric and magnetic fields in crystals is not straightforward as the position operator is ill defined.We present a reformulation of the density matrix perturbation theory for time-dependent electromagnetic fields under periodic boundary conditions,which allows us to treat the orbital magneto-optical response of solids at the ab initio level.The efficiency of the computational scheme proposed is comparable to standard linearresponse calculations of absorption spectra and the results of tests for molecules and solids agree with the available experimental data.A clear signature of the valley Zeeman effect is revealed in the continuum magneto-optical spectrum of a single layer of hexagonal boron nitride.The present formalism opens the path towards the study of magneto-optical effects in strongly driven low-dimensional systems. 展开更多
关键词 PERIODIC MAGNETO SOLIDS
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