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Condens. Matter, Volume 6, Issue 3 (September 2021) – 13 articles

Cover Story (view full-size image): We investigate the orbital resp. band character of holes doped into infinite-layered nickelates. These were recently developed as sister systems to high-temperature cuprate superconductors, which had already been discovered by Bednorz and Muller in 1986 but still command high interest. In both families, the x2–y2 orbital on Cu resp. Ni tends to be close to half filling in insulating layers. However, the charge transfer energy is larger in nickelates, which pushes other Ni orbitals into reach upon doping. Moreover, these other orbitals hybridize with very itinerant rare earth bands such that screening can be expected to be strong. We investigate an effective two-band model with orbitals of x2–y2 and s symmetries and predict two antiferromagnetic states. View this paper.
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11 pages, 4149 KiB  
Article
Sol–Gel Synthesis of Dy Co-Doped ZnO:V Nanoparticles for Optoelectronic Applications
by Fatemah F. Al-Harbi and Jaber Mohamed El Ghoul
Condens. Matter 2021, 6(3), 35; https://doi.org/10.3390/condmat6030035 - 18 Sep 2021
Cited by 5 | Viewed by 2863
Abstract
In this paper, Dy co-doped ZnO:V1% was prepared using the sol–gel process. We studied the impact of doping on the physical properties of the synthesized nanoparticles. In our synthetic approach, under an esterification reaction the release of water was carried out slowly, [...] Read more.
In this paper, Dy co-doped ZnO:V1% was prepared using the sol–gel process. We studied the impact of doping on the physical properties of the synthesized nanoparticles. In our synthetic approach, under an esterification reaction the release of water was carried out slowly, and this step was followed by drying beyond the critical point of ethanol then by calcination in air at 500 °C for 2 h. The structural and morphological studies show the presence of wurtzite structure with an average crystallite size of about 30 nm. In addition, no secondary phase was detected, which shows that the doping elements reacted with the matrix. The reflectance measurements show that by increasing the doping concentration the energy of the band gap energy decreases. Photoluminescence (PL) indicates the presence of two emission bands situated at around 481 nm and 577 nm linked to doping with Dy. Full article
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19 pages, 781 KiB  
Article
The Role of Orbital Nesting in the Superconductivity of Iron-Based Superconductors
by Raquel Fernández-Martín, María J. Calderón, Laura Fanfarillo and Belén Valenzuela
Condens. Matter 2021, 6(3), 34; https://doi.org/10.3390/condmat6030034 - 14 Sep 2021
Cited by 1 | Viewed by 2305
Abstract
We analyze the magnetic excitations and the spin-mediated superconductivity in iron-based superconductors within a low energy model that operates in the band basis, but fully incorporates the orbital character of the spin excitations. We show how the orbital selectivity, encoded in our low [...] Read more.
We analyze the magnetic excitations and the spin-mediated superconductivity in iron-based superconductors within a low energy model that operates in the band basis, but fully incorporates the orbital character of the spin excitations. We show how the orbital selectivity, encoded in our low energy description, simplifies substantially the analysis and allows for analytical treatments, while retaining all the main features of both spin excitations and gap functions computed using multiorbital models. Importantly, our analysis unveils the orbital matching between the hole and electron pockets as the key parameter to determine the momentum dependence and the hierarchy of the superconducting gaps, instead of the Fermi surface matching, as in the common nesting scenario. Full article
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11 pages, 564 KiB  
Article
Character of Doped Holes in Nd1−xSrxNiO2
by Tharathep Plienbumrung, Michael Thobias Schmid, Maria Daghofer and Andrzej M. Oleś
Condens. Matter 2021, 6(3), 33; https://doi.org/10.3390/condmat6030033 - 19 Aug 2021
Cited by 6 | Viewed by 2982
Abstract
We investigate charge distribution in the recently discovered high-Tc superconductors, layered nickelates. With increasing value of charge-transfer energy, we observe the expected crossover from the cuprate to the local triplet regime upon hole doping. We find that the dp [...] Read more.
We investigate charge distribution in the recently discovered high-Tc superconductors, layered nickelates. With increasing value of charge-transfer energy, we observe the expected crossover from the cuprate to the local triplet regime upon hole doping. We find that the dp Coulomb interaction Udp makes Zhang-Rice singlets less favorable, while the amplitude of local triplets at Ni ions is enhanced. By investigating the effective two-band model with orbitals of x2y2 and s symmetries we show that antiferromagnetic interactions dominate for electron doping. The screened interactions for the s band suggest the importance of rare-earth atoms in superconducting nickelates. Full article
(This article belongs to the Special Issue Quantum Complex Matter from Charge Density Waves to Superstripes)
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9 pages, 2077 KiB  
Article
Stress and Strain Prediction of Zirconium Nitride under Oxygen Doping and Vacancy Introduction
by Junfei Cai, Sicheng Wu and Jinjin Li
Condens. Matter 2021, 6(3), 32; https://doi.org/10.3390/condmat6030032 - 18 Aug 2021
Cited by 1 | Viewed by 2275
Abstract
Zirconium nitride (ZrN) is an important material for the mechanical industries due to its excellent properties such as excellent wear resistance, high hardness, etc. In practical applications, it is necessary to study how to regulate the mechanical properties of materials to meet the [...] Read more.
Zirconium nitride (ZrN) is an important material for the mechanical industries due to its excellent properties such as excellent wear resistance, high hardness, etc. In practical applications, it is necessary to study how to regulate the mechanical properties of materials to meet the needs of different applications. To better understand the influence of vacancies and oxygen on the mechanical property of ZrN, we studied the tensile strength of the ZrN with oxygen atom doping and zirconium vacancy introduction by ab initio density functional theory. The mechanical property changes of modified ZrN in three crystallographic directions (<001>, <110>, and <111>) were calculated. The results show that the tensile strength of ZrN can be increased by oxygen doping at a certain concentration, while that of ZrN can be decreased by the introduction of zirconium vacancy. Full article
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13 pages, 3554 KiB  
Article
Electron Lone-Pairs Stereochemistry and Drastic van der Waals and Pressure Effects in AsF3 from First Principles
by Jean Galy and Samir F. Matar
Condens. Matter 2021, 6(3), 31; https://doi.org/10.3390/condmat6030031 - 12 Aug 2021
Cited by 2 | Viewed by 2798
Abstract
AsF3E as a representative of a molecular crystal has been chosen to find the precise localization of the lone pair (LP) E centroid 4s2 of As3+ and to enlighten the behavior of lone pair triplets of fluorine atoms. Starting [...] Read more.
AsF3E as a representative of a molecular crystal has been chosen to find the precise localization of the lone pair (LP) E centroid 4s2 of As3+ and to enlighten the behavior of lone pair triplets of fluorine atoms. Starting from stereochemistry rationale, Density Functional (DFT) electronic structure calculations yielding the electron localization (ELF) mapping led to precise large crystal structure evolutions from basic X-rays data (V = 267.2Å3 at 193K), to (V = 230.5Å3) and under Van der Waals forces (DEW) V = 206.4Å3, and then under pressure P, all illustrated with ELF maps and band structures. Calibrated pressures up to 100 GPa exhibit the remarkable shrinking of all inter-atomic distances including As-E from 0.94Å down to 0.46Å, while the major three bonds As-F1, As-F2 and As-F3 are continuously expanding. The resulting picture of the application of pressure on AsF3 molecular structure leads to the progressive immersion of the 4s2 doublet within the electronic cloud with an original new status of As with its 4s2 E expressed as [AsE]3+. The expanded size becomes close to big LP-free K+, Ba2+ cations or LP characterized bismuth cation: [BiE]3+, which appear inserted in cubes or square anti-prisms with coordination number 8 (CN8) or in tricapped trigonal prisms with CN9. Full article
(This article belongs to the Section Condensed Matter Theory)
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20 pages, 9894 KiB  
Article
Horocycles of Light in a Ferrocell
by Alberto Tufaile, Michael Snyder and Adriana Pedrosa Biscaia Tufaile
Condens. Matter 2021, 6(3), 30; https://doi.org/10.3390/condmat6030030 - 10 Aug 2021
Cited by 5 | Viewed by 4978
Abstract
We studied the effects of image formation in a device known as Ferrocell, which consists of a thin film of a ferrofluid solution between two glass plates subjected to an external magnetic field in the presence of a light source. Following suggestions found [...] Read more.
We studied the effects of image formation in a device known as Ferrocell, which consists of a thin film of a ferrofluid solution between two glass plates subjected to an external magnetic field in the presence of a light source. Following suggestions found in the literature, we compared the Ferrocell light scattering for some magnetic field configurations with the conical scattering of light by thin structures found in foams known as Plateau borders, and we discuss this type of scattering with the concept of diffracted rays from the Geometrical Theory of Diffraction. For certain magnetic field configurations, a Ferrocell with a point light source creates images of circles, parabolas, and hyperboles. We interpret the Ferrocell images as analogous to a Möbius transformation by inversion of the magnetic field. The formation of circles through this transformation is known as horocycles, which can be observed directly in the Ferrocell plane. Full article
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20 pages, 636 KiB  
Article
Convergence of Coupling-Parameter Expansion-Based Solutions to Ornstein–Zernike Equation in Liquid State Theory
by S. V. G. Menon
Condens. Matter 2021, 6(3), 29; https://doi.org/10.3390/condmat6030029 - 5 Aug 2021
Cited by 1 | Viewed by 2199
Abstract
The objective of this paper is to investigate the convergence of coupling-parameter expansion-based solutions to the Ornstein–Zernike equation in liquid state theory. The analytically solved Baxter’s adhesive hard sphere model is analyzed first by using coupling-parameter expansion. It was found that the expansion [...] Read more.
The objective of this paper is to investigate the convergence of coupling-parameter expansion-based solutions to the Ornstein–Zernike equation in liquid state theory. The analytically solved Baxter’s adhesive hard sphere model is analyzed first by using coupling-parameter expansion. It was found that the expansion provides accurate approximations to solutions—including the liquid-vapor phase diagram—in most parts of the phase plane. However, it fails to converge in the region where the model has only complex solutions. Similar analysis and results are obtained using analytical solutions within the mean spherical approximation for the hardcore Yukawa potential. However, numerical results indicate that the expansion converges in all regions in this model. Next, the convergence of the expansion is analyzed for the Lennard-Jones potential by using an accurate density-dependent bridge function in the closure relation. Numerical results are presented which show convergence of correlation functions, compressibility versus density profiles, etc., in the single as well as two-phase regions. Computed liquid-vapor phase diagrams, using two independent schemes employing the converged profiles, compare excellently with simulation data. The results obtained for the generalized Lennard-Jones potential, with varying repulsive exponent, also compare well with the simulation data. Solution-spaces and the bifurcation of the solutions of the Ornstein–Zernike equation that are relevant to coupling-parameter expansion are also briefly discussed. All of these results taken together establish the coupling-parameter expansion as a practical tool for studying single component fluid phases modeled via general pair-potentials. Full article
(This article belongs to the Section Condensed Matter Theory)
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11 pages, 1425 KiB  
Article
Positron Annihilation Spectroscopy as a Diagnostic Tool for the Study of LiCoO2 Cathode of Lithium-Ion Batteries
by Gioele Pagot, Valerio Toso, Bernardo Barbiellini, Rafael Ferragut and Vito Di Noto
Condens. Matter 2021, 6(3), 28; https://doi.org/10.3390/condmat6030028 - 29 Jul 2021
Cited by 5 | Viewed by 3365
Abstract
Positron annihilation spectroscopy using lifetime and Doppler broadening allows the characterization of the lithiation state in LiCoO2 thin film used in cathode of lithium-ion batteries. The lifetime results reflect positron spillover because of the presence of graphite in between the oxide grains [...] Read more.
Positron annihilation spectroscopy using lifetime and Doppler broadening allows the characterization of the lithiation state in LiCoO2 thin film used in cathode of lithium-ion batteries. The lifetime results reflect positron spillover because of the presence of graphite in between the oxide grains in real cathode Li-ion batteries. This spillover produces an effect in the measured positron parameters which are sensitive to delocalized electrons from lithium atoms as in Compton scattering results. The first component of the positron lifetime corresponds to a bulk-like state and can be used to characterize the state of charge of the cathode while the second component represents a surface state at the grain-graphite interface. Full article
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11 pages, 1526 KiB  
Article
Cross-Investigation on Copper Nitroprusside: Combining XRD and XAS for In-Depth Structural Insights
by Angelo Mullaliu, Giuliana Aquilanti, Jasper Rikkert Plaisier and Marco Giorgetti
Condens. Matter 2021, 6(3), 27; https://doi.org/10.3390/condmat6030027 - 25 Jul 2021
Cited by 5 | Viewed by 2810
Abstract
The emerging energy demand and need to develop sustainable energy storage systems have drawn extensive attention to fundamental and applied research. Anion redox processes were proposed in cathodic materials in addition to traditional transition metal redox to boost the specific capacity and the [...] Read more.
The emerging energy demand and need to develop sustainable energy storage systems have drawn extensive attention to fundamental and applied research. Anion redox processes were proposed in cathodic materials in addition to traditional transition metal redox to boost the specific capacity and the electrochemical performance. Alternatively, copper nitroprusside (CuNP) features an electroactive nitrosyl ligand alongside the two structural metals (Fe, Cu), representing an alternative to anion redox in layered oxides. Here, a deep structural investigation is carried out on CuNP by complementing the long-range order sensitivity of X-ray diffraction (XRD) and the local atomic probe of X-ray absorption (XAS). Two different CuNP materials are studied, the hydrated and dehydrated forms. A new phase for hydrated CuNP not reported in the literature is solved, and Rietveld refined. The XAS spectra of the two materials at the Cu and Fe K-edges show a similar yet different atomic environment. The extended XAS spectra (EXAFS) analysis is accomplished by considering three- and four-body terms due to the high collinearity of the atomic chains and gives accurate insight into the first-, second-, and third-shell interatomic distances. Both materials are mounted in Li-ion and Na-ion cells to explore the link between structure and electrochemical performance. As revealed by the charge/discharge cycles, the cyclability in Na-ion cells is negatively affected by interstitial water. The similarity in the local environment and the electrochemical differences suggest a long-range structural dependence on the electrochemical performance. Full article
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4 pages, 181 KiB  
Editorial
Study of Rechargeable Batteries Using Advanced Spectroscopic and Computational Techniques
by Bernardo Barbiellini, Jan Kuriplach and Rolando Saniz
Condens. Matter 2021, 6(3), 26; https://doi.org/10.3390/condmat6030026 - 25 Jul 2021
Cited by 1 | Viewed by 2169
Abstract
Improving the efficiency and longevity of energy storage systems based on Li- and Na-ion rechargeable batteries presents a major challenge. The main problems are essentially capacity loss and limited cyclability. These effects are due to a hierarchy of factors spanning various length and [...] Read more.
Improving the efficiency and longevity of energy storage systems based on Li- and Na-ion rechargeable batteries presents a major challenge. The main problems are essentially capacity loss and limited cyclability. These effects are due to a hierarchy of factors spanning various length and time scales, interconnected in a complex manner. As a consequence, and in spite of several decades of research, a proper understanding of the ageing process has remained somewhat elusive. In recent years, however, combinations of advanced spectroscopy techniques and first-principles simulations have been applied with success to tackle this problem. In this Special Issue, we are pleased to present a selection of articles that, by precisely applying these methods, unravel key aspects of the reduction–oxidation reaction and intercalation processes. Furthermore, the approaches presented provide improvements to standard diagnostic and characterisation techniques, enabling the detection of possible Li-ion flow bottlenecks causing the degradation of capacity and cyclability. Full article
7 pages, 1422 KiB  
Communication
Charge Order and Suppression of Superconductivity in HgBa2CuO4+d at High Pressures
by Manuel Izquierdo, Daniele C. Freitas, Dorothée Colson, Gastón Garbarino, Anne Forget, Helène Raffy, Jean-Paul Itié, Sylvain Ravy, Pierre Fertey and Manuel Núñez-Regueiro
Condens. Matter 2021, 6(3), 25; https://doi.org/10.3390/condmat6030025 - 23 Jul 2021
Cited by 4 | Viewed by 2181
Abstract
New insight into the superconducting properties of HgBa2CuO4 (Hg-1201) cuprates is provided by combined measurements of electrical resistivity and single crystal X-ray diffraction under pressure. The changes induced by increasing pressure up to 20 GPa in optimally doped [...] Read more.
New insight into the superconducting properties of HgBa2CuO4 (Hg-1201) cuprates is provided by combined measurements of electrical resistivity and single crystal X-ray diffraction under pressure. The changes induced by increasing pressure up to 20 GPa in optimally doped single crystals were investigated. The resistivity measurements as a function of temperature show a metallic behavior up to ~10 GPa that gradually passes into an insulating state, typical of charge ordering, which totally suppresses superconductivity above 13 GPa. The changes in resistivity are accompanied by the apparition of sharp Bragg peaks in the X-ray diffraction patterns, indicating that the charge ordering is accompanied by a 3D oxygen ordering. Considering that pressure induces a charge transfer of about 0.02 at 10 GPa, our results are the first observation of charge order competing with superconductivity developed in the overdoped region of the phase diagram of a Hg-based cuprate. Full article
(This article belongs to the Special Issue Quantum Complex Matter from Charge Density Waves to Superstripes)
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13 pages, 618 KiB  
Article
Effective-Field Theory for Model High-Tc Cuprates
by Alexander Moskvin and Yuri Panov
Condens. Matter 2021, 6(3), 24; https://doi.org/10.3390/condmat6030024 - 19 Jul 2021
Cited by 5 | Viewed by 2029
Abstract
Starting with a minimal model for the CuO2 planes with the on-site Hilbert space reduced to only three effective valence centers [CuO4]7,6,5 (nominally Cu1+,2+,3+ [...] Read more.
Starting with a minimal model for the CuO2 planes with the on-site Hilbert space reduced to only three effective valence centers [CuO4]7,6,5 (nominally Cu1+,2+,3+) with different conventional spin and different orbital symmetry, we propose a unified non-BCS model that allows one to describe the main features of the phase diagrams of doped cuprates within the framework of a simple effective field theory. Unconventional bosonic superconducting phase related with a two-particle quantum transport is shown to compete with antiferromagnetic insulating phase, charge order, and metallic Fermi liquid via phase separation regime. Full article
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7 pages, 218 KiB  
Editorial
Terahertz as a Frontier Area for Science and Technology
by Akinori Irizawa, Stefano Lupi and Augusto Marcelli
Condens. Matter 2021, 6(3), 23; https://doi.org/10.3390/condmat6030023 - 28 Jun 2021
Cited by 7 | Viewed by 2710
Abstract
Recent theoretical and experimental research is triggering interest to technologies based on radiation in the region from ~0.1 to 20 Terahertz (THz). Today, this region of the electromagnetic (e.m.) spectrum is a frontier area for research in many disciplines. The technological roadmap of [...] Read more.
Recent theoretical and experimental research is triggering interest to technologies based on radiation in the region from ~0.1 to 20 Terahertz (THz). Today, this region of the electromagnetic (e.m.) spectrum is a frontier area for research in many disciplines. The technological roadmap of the THz radiation considers outdoor and indoor communications, security, drug detection, biometrics, food quality control, agriculture, medicine, semiconductors, and air pollution, and demands high-power and sub-ps compact sources, modern detectors, and new integrated systems. There are still many open questions regarding working at THz frequencies and with THz radiation. In particular, we need to invest in new methodologies and in materials exhibiting the unusual or exotic properties of THz. This book contains original papers dealing with some emerging THz applications, new devices, sources and detectors, and materials with advanced properties for applications in biomedicine, cultural heritage, technology, and space. Full article
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