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Nanoscale Structural Phase Transitions in Aqueous Solutions of Organic Molecules 有机分子水溶液中的纳米级结构相变
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-26 DOI: 10.3390/condmat8030064
N. Bunkin, L. Sabirov, D. Semenov, F. Ismailov, M. Khasanov
Adiabatic compressibility βS of the 4-methylpyridine + water solution is investigated in a wide concentration and temperature variation interval using Mandelstam–Brillouin scattering spectroscopy. The adiabatic compressibility minimum caused by the microinhomogeneous structure of the solution is experimentally established at the concentration of 0.06 molar fractions of 4-methylpyridine in the solution. The results of the investigations allow the construction of a diagram of possible states caused by a continuous three-dimensional hydrogen bond network of water. The results of experimental study of the excessive hypersound absorption in acetone + water and 3-methylpyridine + water solutions are discussed based on the conclusions of the theory of high-frequency sound scattering near the critical point (developed by Chaban) and the Landau theory. These results are described within the framework of the Landau and Chaban theories and explained by the existence of two different states with minimum thermodynamic stability in the solution.
用曼德尔斯塔姆-布里渊散射光谱法研究了4-甲基吡啶+水溶液在较宽浓度和温度变化区间内的绝热压缩率βS。在溶液中4-甲基吡啶浓度为0.06摩尔分数时,实验确定了由溶液微非均质结构引起的绝热可压缩性最小值。研究结果允许构建一个由连续的三维水氢键网络引起的可能状态的图表。根据Chaban提出的临界点附近高频声散射理论和朗道理论的结论,讨论了丙酮+水和3-甲基吡啶+水溶液中超声吸收的实验研究结果。这些结果是在朗道和查班理论的框架内描述的,并通过溶液中存在两种具有最小热力学稳定性的不同状态来解释。
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引用次数: 0
Exploring Photonic Crystals: Band Structure and Topological Interface States 探索光子晶体:能带结构和拓扑界面态
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-25 DOI: 10.3390/condmat8030063
M. de Dios‐Leyva, Andy Márquez-González, C. Duque
The physical mechanisms supporting the existence of topological interface modes in photonic structures, formed with the concatenation of two finite, N-period, one-dimensional photonic crystals, are investigated. It is shown that these mechanisms originate from a specific configuration of bands and bandgaps of topological origin in the band structure of the concatenated structure. Our analysis reveals that the characteristics of such a configuration depend on the structural parameters, including the number, N, of unit cells, and determine the properties of the corresponding resonant transmission peak. It was shown that the width and maximum value of the transmission peaks decrease with N. These results not only provide new physical insight into the origin and nature of such modes, but also can be used to control and manipulate the transmission peak properties, such as peak values, full width at half maximum (FWHM), and Q-factor, which are of special interest in the fields of optical sensing, filters, etc.
研究了由两个有限n周期一维光子晶体拼接而成的光子结构中支持拓扑界面模式存在的物理机制。结果表明,这些机制源于连接结构的带结构中特定的带构型和拓扑起源的带隙。我们的分析表明,这种结构的特性取决于结构参数,包括单元胞的数量N,并决定了相应的谐振透射峰的特性。结果表明,透射峰的宽度和最大值随n的增加而减小。这些结果不仅为这种模式的起源和性质提供了新的物理见解,而且可以用于控制和操纵传输峰的特性,如峰值、半峰全宽度(FWHM)和q因子,这些特性在光学传感、滤波器等领域中具有特殊的意义。
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引用次数: 0
The Synthesis of C70 Fullerene Nanowhiskers Using the Evaporating Drop Method 蒸发液滴法合成C70富勒烯纳米晶须
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-24 DOI: 10.3390/condmat8030062
Sagdulla A. Bakhramov, U. Makhmanov, Bobirjon A. Aslonov
Semiconductor nanowhiskers, particularly nanostructured whiskers based on zero-dimensional (0D) C70 fullerene, are being actively discussed due to the great potential of their application in modern electronics. For the first time, we proposed and implemented a method for the synthesis of nanostructured C70 fullerene whiskers based on the self-organization of C70 molecules during the thermal evaporation of C70 droplets on the substrate surface. We found that the onset of the synthesis of C70 nanowhiskers upon the evaporation of drops of a C70 solution in toluene on the substrate surface depends on the substrate temperature. We have provided experimental evidence that an increase in both the C70 concentration in the initial drop and the substrate temperature leads to an increase in the geometric dimensions of C70 nanowhiskers. The obtained results provide useful vision on the role of solute concentration and substrate temperature in the synthesis of one-dimensional materials.
半导体纳米晶须,特别是基于零维C70富勒烯的纳米结构晶须,由于其在现代电子学中的巨大应用潜力而受到人们的积极讨论。本文首次提出并实现了一种基于C70分子在基体表面热蒸发过程中自组织的C70富勒烯晶须合成方法。我们发现C70纳米晶须的合成开始于C70溶液在甲苯中的液滴在衬底表面的蒸发,这取决于衬底温度。我们已经提供了实验证据,表明C70浓度的增加和衬底温度的升高都会导致C70纳米晶须几何尺寸的增加。所得结果为研究溶质浓度和底物温度在一维材料合成中的作用提供了有益的视角。
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引用次数: 0
Multiband Superconductivity in High-Pressure Sulfur Hydrides 高压硫氢化物中的多带超导性
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-20 DOI: 10.3390/condmat8030069
G. Ummarino, A. Bianconi
The temperature dependence of the two superconducting gaps in pressurised H3S at 155 GPa with a critical temperature of 203 K has been determined using a data analysis of the experimental curve of the upper critical magnetic field as a function of temperature in the framework of the two-band s-wave Eliashberg theory. Two different phonon-mediated intra-band Cooper pairing channels in a regime of moderate strong couplings have the key role of the pair-exchange interaction between the two gaps, giving the two non-diagonal terms of the coupling tensor, which are missing in the single-band s-wave Eliashberg theory. The results provide a prediction of the different temperature dependence of the small and large gaps as a function of temperature, which provides evidence of multigap superconductivity in H3S.
在双频s波Eliashberg理论的框架下,使用对作为温度函数的上临界磁场的实验曲线的数据分析,确定了在临界温度为203K的155GPa加压H3S中两个超导间隙的温度依赖性。在中等强度耦合的情况下,两个不同的声子介导的带内库珀配对通道在两个间隙之间的对交换相互作用中起着关键作用,给出了耦合张量的两个非对角项,这在单带s波Eliashberg理论中是缺失的。这些结果预测了作为温度函数的小间隙和大间隙的不同温度依赖性,这为H3S中的多间隙超导性提供了证据。
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引用次数: 0
Structural, Electronic, and Optical Properties of Wurtzite VxAl1−xN Alloys: A First-Principles Study 纤锌矿VxAl1−xN合金的结构、电子和光学性质:第一性原理研究
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-19 DOI: 10.3390/condmat8030061
G. E. Escorcia-Salas, Diego Restrepo-Leal, Oscar Martinez-Castro, W. López‐Pérez, J. Sierra-Ortega
We present a comprehensive study on the structural, electronic, and optical properties of VxAl1−xN ternary alloys using first-principles calculations. Our investigations employ the full-potential linearized augmented-plane-wave (FP-LAPW) method within the density functional theory (DFT) framework. The impact of varying vanadium composition (x = 0, 0.25, 0.5, 0.75, 1) on the structural, electronic, and optical characteristics of wurtzite VxAl1−xN alloys is examined in detail. Our findings reveal a distinct nonlinear relationship between the lattice constant, bulk modulus, and the concentration of vanadium (x) in the VxAl1−xN alloys. An analysis of the electronic band structures and densities of states reveals a metallic behavior in the VxAl1−xN alloys, primarily driven by the V-d states near the Fermi energy. These results shed light on the electronic properties of the alloys, contributing to a deeper understanding of their potential for various applications. Furthermore, we calculate various optical properties, including the real and imaginary dielectric functions, refractive index, energy loss spectrum, and reflectivity. The obtained optical functions provide valuable insights into the optical behavior of the VxAl1−xN alloys. The results contribute to the fundamental knowledge of these materials and their potential applications in various fields.
我们使用第一性原理计算对VxAl1−xN三元合金的结构、电子和光学性质进行了全面的研究。本研究采用密度泛函理论(DFT)框架下的全势线性化增强平面波(FP-LAPW)方法。详细研究了不同钒组分(x = 0、0.25、0.5、0.75、1)对纤锌矿VxAl1−xN合金结构、电子和光学特性的影响。我们的研究结果揭示了VxAl1−xN合金中晶格常数、体积模量和钒(x)浓度之间存在明显的非线性关系。电子能带结构和态密度的分析揭示了VxAl1 - xN合金的金属行为,主要是由费米能量附近的V-d态驱动的。这些结果揭示了合金的电子特性,有助于更深入地了解它们在各种应用中的潜力。此外,我们计算了各种光学性质,包括实和虚介电函数、折射率、能量损失谱和反射率。获得的光学函数为VxAl1−xN合金的光学行为提供了有价值的见解。这些结果有助于了解这些材料的基本知识及其在各个领域的潜在应用。
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引用次数: 0
Theoretical Study of Electronic and Thermal Transport Properties through a Single-Molecule Junction of Catechol 邻苯二酚单分子结的电子和热输运性质的理论研究
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-15 DOI: 10.3390/condmat8030060
E. Y. Soto-Gómez, Judith Helena Ojeda Silva, J. A. Gil-Corrales, Daniel Gallego, Mikel F. Hurtado Morales, Á. Morales, C. Duque
The study of molecular nanoelectronic devices has recently gained significant interest, especially their potential use as functional junctions of molecular wires. Aromatic systems with π-conjugated bonds within their chemical backbones, such as catechol, have attracted particular attention in this area. In this work, we focused on calculating and determining catechol’s electrical and thermal transport properties using the theoretical method of Green’s functions renormalized in a real space domain within a framework of tight-binding approximation to the first neighbors. Thus, we studied two theoretical models of catechol as a function of its geometry, obtaining striking variations in the profiles of electrical and thermal conductance, the Seebeck coefficient, and the figure of merit. The analyses of the results suggest the potential application of catechol as a likely conductive and thermoelectric molecule serving as a novel material to use in molecular electronic devices.
分子纳米电子器件的研究最近引起了人们的极大兴趣,尤其是它们作为分子线的功能结的潜在用途。在其化学主链中具有π-共轭键的芳香体系,如邻苯二酚,在这一领域引起了特别的关注。在这项工作中,我们专注于使用格林函数的理论方法来计算和确定邻苯二酚的电输运和热输运性质,该方法在第一邻居的紧束缚近似框架内在实空间域中进行重整。因此,我们研究了邻苯二酚作为其几何结构函数的两个理论模型,获得了电导率和热导率、塞贝克系数和品质因数的显著变化。结果分析表明,邻苯二酚作为一种可能的导电和热电分子,作为一种用于分子电子器件的新型材料,具有潜在的应用前景。
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引用次数: 0
On the Optical Properties of Cr2Ge2Te6 and Its Heterostructure Cr2Ge2Te6的光学性质及其异质结构
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-14 DOI: 10.3390/condmat8030059
H. Idzuchi, A. E. Llacsahuanga Allcca, A. Haglund, X. Pan, T. Matsuda, K. Tanigaki, D. Mandrus, Yong P Chen
Recently, there has been a growing interest in two-dimensional van der Waals (vdW) magnets owing to their unique two-dimensional magnetic phenomena and potential applications. Most vdW ferromagnets have the Curie temperature below room temperature, highlighting the need to explore how to enhance their magnetism. In our previous report, we successfully increased the Curie temperature of the prototypical vdW magnet Cr2Ge2Te6 using a NiO overlayer. In layered materials, the presence of wrinkles is often observed and evaluating them using optical microscopy proves to be useful; however, there have been limited investigations into the optical constants of vdW magnets, hampering progress in understanding their optical properties. In this study, we present the optical constants of Cr2Ge2Te6 obtained through ellipsometry measurements. To account for the presence of wrinkles, we model a vacuum region between the substrate and the vdW magnet, and we calculate the reflectivity as a function of wavelength and vacuum thickness to visualize the optical image. Furthermore, we discuss the relationship between the optical constants and the electronic structure of the material.
近年来,由于二维范德华磁体独特的二维磁现象和潜在的应用,人们对其越来越感兴趣。大多数vdW铁磁体的居里温度低于室温,这突出了探索如何增强其磁性的必要性。在我们之前的报告中,我们使用NiO覆盖层成功地提高了原型vdW磁体Cr2Ge2Te6的居里温度。在层状材料中,经常观察到褶皱的存在,并且使用光学显微镜对其进行评估被证明是有用的;然而,对vdW磁体的光学常数的研究有限,阻碍了理解其光学性质的进展。在本研究中,我们给出了通过椭圆偏振测量获得的Cr2Ge2Te6的光学常数。为了说明褶皱的存在,我们对衬底和vdW磁体之间的真空区域进行建模,并计算反射率作为波长和真空厚度的函数,以可视化光学图像。此外,我们还讨论了光学常数与材料电子结构之间的关系。
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引用次数: 0
The Effect of Acyl Chain Position on the 2D Monolayer Formation of Monoacyl-sn-Glycerol at the Air/Water Interface: Quantum Chemical Modeling 在空气/水界面上酰基链位置对单酰基-sn-甘油二维单层形成的影响:量子化学模型
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-13 DOI: 10.3390/condmat8030058
E. S. Kartashynska
This paper deals with the results of quantum chemical modeling of the monoacyl-sn-glycerol 2D cluster formation at the air/water interface using a semi-empirical PM3 method. The impact of the 2 or 3 positions of the acyl substituent on the thermodynamics of the monolayer formation is assessed for surfactants with an acyl substituent CnH2n+1COO chain length of n = 6–17 carbon atoms. The calculation shows a significant change in the spontaneous clusterization threshold for isomeric compounds, which differs only in the position of the acyl substituent with respect to the glycerol backbone. This change is almost equal to substituent shortening by approximately two methylene fragments. At the same time, the geometric parameters of the unit cell for resulting monolayers are not affected so drastically. The 2D films in question possess an oblique or orthorhombic unit cell with parameters for 2 and 3-monoacyl-sn-glycerol monolayers, as follows: a = 4.91 Å and 4.82 Å and b = 5.00 Å and 4.92 Å, with hydrocarbon chains tilted at t = 23.0° and 23.5°. The calculated results are in accordance with existing experimental data obtained using grazing incidence X-ray diffraction measurements and the π-A isotherm technique.
本文讨论了利用半经验PM3方法在空气/水界面上形成单酰基-sn-甘油二维团簇的量子化学建模结果。对于链长为n = 6-17个碳原子的酰基取代基CnH2n+1COO的表面活性剂,评估了酰基取代基的2或3个位置对单层形成热力学的影响。计算结果表明,同分异构体化合物的自发簇化阈值发生了显著变化,仅在酰基取代基相对于甘油主链的位置上有所不同。这个变化几乎等于取代基缩短了大约两个亚甲基片段。同时,所得到的单层的单元胞的几何参数不会受到如此大的影响。所讨论的二维薄膜具有斜晶或正交晶胞,其参数为2和3-单酰基-锡-甘油单层:a = 4.91 Å和4.82 Å, b = 5.00 Å和4.92 Å,烃链在t = 23.0°和23.5°倾斜。计算结果与已有的掠入射x射线衍射测量和π-A等温线技术得到的实验数据一致。
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引用次数: 0
Tensile Microstrain Fluctuations in the BaPbO Units in Superconducting BaPb1−xBixO3 by Scanning Dispersive Micro-XANES 扫描分散微XANES研究BaPb1−xBixO3超导材料中BaPbO单元的拉伸微应变
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-11 DOI: 10.3390/condmat8030057
Ruben Albertini, S. Macis, A. Ivanov, A. Menushenkov, A. Puri, V. Monteseguro, Boby Joseph, Wei Xu, A. Marcelli, P. Giraldo-Gallo, I. Fisher, A. Bianconi, G. Campi
BaPb1−xBixO3 (BPBO) bismuthate, showing high TC superconductivity for 0.05 < x < 0.35, is an archetypal system for studying the complex inhomogeneity of perovskite lattice favoring the emergence of quantum coherence, called the superstripes phase. Local lattice fluctuations, detected by EXAFS; nanoscale stripes, detected by electron microscopy; and two competing crystalline structures, detected by diffraction, are known to characterize the superconducting phase. At nanoscale [BaBiO3] centered nanoscale units (BBO) coexist with BaPbO3 centered (BPO) units in the BPBO perovskite; therefore, we expect a tensile microstrain in BPO units due the misfit strain between the two different lattices. Here, we report the measurement of the spatial micro-fluctuations of the local tensile microstrain ε in the BaPO units in superconducting Ba(Pb1−xBix)O3 crystals with x1 = 0.19 an x2 = 0.28. We show here the feasibility of applying the scanning dispersive micro-X-ray absorption near edge structure (SdμXANES) technique, using focused synchrotron radiation, to probe the microscale spatial fluctuations of the microstrain in BPO units. This unconventional real-space SdμXANES microscopy at the Pb L3 edge has been collected in the dispersive mode. Our experimental method allows us to measure either the local Bi chemical concentration x and the local lattice microstrain of local BBO and BPO units. The 5 × 5 micron-size spots from the focused X-ray beam allowed us to obtain maps of 1600 points covering an area of 200 × 200 microns. The mapping shows a substantial difference between the spatial fluctuations of the microstrain ε and the chemical inhomogeneity x. Moreover, we show the different relations ε(x) in samples with lower (x1 = 0.19) and higher (x2 = 0.28) doping respect to the optimum doping (x = 0.25).
BaPb1−xBixO3(BPBO)铋酸盐显示出0.05<x<0.35的高TC超导性,是研究钙钛矿晶格复杂不均匀性的原型系统,有利于量子相干性的出现,称为超成熟相。EXAFS检测到的局部晶格波动;电子显微镜检测到的纳米级条纹;通过衍射检测到的两种相互竞争的晶体结构可以表征超导相。在纳米尺度上,以[BaBiO3]为中心的纳米尺度单元(BBO)与以BaPbO3为中心的(BPO)单元共存于BPBO钙钛矿中;因此,我们预计由于两个不同晶格之间的失配应变,BPO单元中会出现拉伸微应变。在这里,我们报道了在x1=0.19和x2=0.28的超导Ba(Pb1−xBix)O3晶体中BaPO单元中局部拉伸微应变ε的空间微波动的测量。我们在这里展示了应用扫描色散微X射线吸收近边缘结构(SdμXANES)技术,使用聚焦同步辐射,探测BPO单元中微应变的微尺度空间波动的可行性。这种在Pb L3边缘的非常规实空间SdμXANES显微镜是以色散模式收集的。我们的实验方法使我们能够测量局部Bi化学浓度x以及局部BBO和BPO单元的局部晶格微应变。来自聚焦X射线束的5×5微米大小的斑点使我们能够获得覆盖200×200微米区域的1600个点的地图。该映射显示了微应变ε和化学不均匀性x之间的空间波动之间的显著差异。此外,我们显示了较低(x1=0.19)和较高(x2=0.28)掺杂的样品中的ε(x)与最佳掺杂(x=0.25)的不同关系。
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引用次数: 0
Tc Saturation and Possible Electronic Phase Separation in Strongly Overdoped Cuprates 强过量掺杂铜酸盐中的Tc饱和和可能的电子相分离
IF 1.7 Q3 PHYSICS, CONDENSED MATTER Pub Date : 2023-07-05 DOI: 10.3390/condmat8030056
A. Hemmatzade, E. Medina, L. Delbes, B. Baptiste, D. Hrabovský, Y. Klein, S. Conradson, M. Karppinen, A. Gauzzi
In order to elucidate the unusual superconducting properties of cuprates in the strongly overdoped region, i.e., at hole-doping levels p≳0.4/Cu in the CuO2 plane, we study the structural and superconducting properties of a series of Cu0.75Mo0.25Sr2YCu2O7+x powder samples oxygenated under high pressure using different concentrations of KClO3 up to 35 mol %. The analysis of X-ray diffraction data indicates a high purity ∼90% of all samples and suggests that the concentration, x, of extra oxygen atoms increases with increasing KClO3 concentration. Surprisingly, the Tc values remain nearly constant within the 80–85 K range independent of KClO3 concentration, which suggests a scenario of Tc saturation. In order to account for this unexpected behaviour, we put forward the hypothesis that overdoping enhances the density of unpaired holes, which is supported by the observation of large values of the Sommerfeld coefficient in all samples. We therefore propose a scenario of electronic phase separation between normal and superconducting holes.
为了阐明铜酸盐在强过掺杂区(即在CuO2平面p > 0.4/Cu的空穴掺杂水平下)的异常超导性质,我们研究了一系列Cu0.75Mo0.25Sr2YCu2O7+x粉末样品在高压下使用不同浓度(高达35 mol %)的KClO3氧化的结构和超导性质。x射线衍射数据分析表明,所有样品的纯度都很高,约为90%,并表明额外氧原子的浓度x随着KClO3浓度的增加而增加。令人惊讶的是,Tc值在80-85 K范围内几乎保持不变,与KClO3浓度无关,这表明Tc存在饱和。为了解释这种意想不到的行为,我们提出了一个假设,即过量掺杂增强了未配对空穴的密度,这一假设得到了在所有样品中观察到的大值索默菲尔德系数的支持。因此,我们提出了正常空穴和超导空穴之间电子相分离的设想。
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引用次数: 0
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Condensed Matter
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