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Keywords = Sr2RuO4

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15 pages, 6277 KiB  
Article
High-Performance Ferroelectric Capacitors Based on Pt/BaTiO3/SrRuO3/SrTiO3 Heterostructures for Nonvolatile Memory Applications
by Zengyuan Fang, Yiming Peng, Haiou Li, Xingpeng Liu and Jianghui Zhai
Crystals 2025, 15(4), 337; https://doi.org/10.3390/cryst15040337 - 2 Apr 2025
Viewed by 757
Abstract
BaTiO3 (BTO), a lead-free chalcogenide ferroelectric material, has emerged as a promising candidate for ferroelectric memories due to its advantageous ferroelectric properties, notable flexibility, and mechanical stability, along with a high dielectric constant and minimal leakage. These attributes lay a crucial foundation [...] Read more.
BaTiO3 (BTO), a lead-free chalcogenide ferroelectric material, has emerged as a promising candidate for ferroelectric memories due to its advantageous ferroelectric properties, notable flexibility, and mechanical stability, along with a high dielectric constant and minimal leakage. These attributes lay a crucial foundation for multi-value storage. In this study, high-quality BaTiO3 ferroelectric thin films have been successfully prepared on STO substrates by pulsed laser deposition (PLD), and Pt/BaTiO3/SrRuO3/SrTiO3 ferroelectric heterojunctions were finally prepared by a combination of UV lithography and magnetron sputtering. Characterization and performance tests were carried out by AFM, XRD, and a semiconductor analyzer. The results demonstrate that the ferroelectric heterojunction prepared in this study exhibits excellent ferroelectric properties. Furthermore, the device demonstrates fatigue-free operation after 107 bipolar switching cycle tests, and the polarization value exhibits no significant decrease in the holding characteristic test at 104 s, thereby further substantiating its exceptional reliability and durability. These findings underscore the considerable promise of BTO ferroelectric memories for nonvolatile storage applications and lay the foundation for the development in the fields of both in-memory computing systems and neuromorphic computing. Full article
(This article belongs to the Special Issue Recent Research on Electronic Materials and Packaging Technology)
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11 pages, 3052 KiB  
Article
Structural, Vibrational, and Dielectric Properties of BiFeO3/LaFeO3 Superlattices Grown on (001)-SrTiO3
by Mouna Khiari, Razvan Burcea, Oana Condurache, Maxime Vallet, Anna Cantaluppi, Amani Melhem, Brahim Dkhil and Houssny Bouyanfif
Electronics 2025, 14(6), 1117; https://doi.org/10.3390/electronics14061117 - 12 Mar 2025
Viewed by 716
Abstract
BiFeO3/LaFeO3 (BFO/LFO) epitaxial superlattices (SLs) with different bilayer thicknesses were grown via pulsed laser deposition on a (001)-SrTiO3 substrate buffered with a SrRuO3 bottom electrode. Room-temperature X-ray diffraction demonstrated strong structural changes in tuning the bilayer thickness while [...] Read more.
BiFeO3/LaFeO3 (BFO/LFO) epitaxial superlattices (SLs) with different bilayer thicknesses were grown via pulsed laser deposition on a (001)-SrTiO3 substrate buffered with a SrRuO3 bottom electrode. Room-temperature X-ray diffraction demonstrated strong structural changes in tuning the bilayer thickness while keeping the total thickness constant. Superlattices with thin periods were characterized by an antiferroelectric Pnma-like phase, while thick bilayers of the SLs were more likely to be described by a mixed state, including a rhombohedral ferroelectric bulk-like phase. Raman scattering analysis further confirmed the structural behaviour deduced by X-ray diffraction. Strain relaxation and symmetry changes were moreover accompanied by modifications in the dielectric properties correlated with the deduced (anti)ferroic structural phases. Full article
(This article belongs to the Special Issue Ferroelectric Materials and Applications)
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13 pages, 1122 KiB  
Article
Simple Model for Tc and Pairing Symmetry Changes in Sr2RuO4 Under (100) Uniaxial Strain
by Macauley Curtis, Martin Gradhand and James F. Annett
Condens. Matter 2024, 9(4), 44; https://doi.org/10.3390/condmat9040044 - 1 Nov 2024
Viewed by 1392
Abstract
Uniaxial strain in the (100) direction has the effect of increasing the superconducting Tc in Sr2RuO4 from 1.5 K to over 3 K. The enhanced Tc corresponds to a Lifshitz transition in the Fermi surface topology of this [...] Read more.
Uniaxial strain in the (100) direction has the effect of increasing the superconducting Tc in Sr2RuO4 from 1.5 K to over 3 K. The enhanced Tc corresponds to a Lifshitz transition in the Fermi surface topology of this unconventional superconductor. We model this using a simple two-dimensional one-band model for the γ sheet of the Fermi surface. This reproduces the experimental Tc results well if we assume a dx2y2 singlet pairing state. On the other hand, the triplet state px+ipy does not show any distinct peaks in Tc associated with the Lifshitz transition. A mixed symmetry state pairing of the form d+ig can both describe the Tc changes and show a distinct transition temperature for time-reversal symmetry breaking (TRSB). Full article
(This article belongs to the Special Issue Superstripes Physics, 3rd Edition)
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9 pages, 1412 KiB  
Article
Coherent Oscillations in a SrRuO3/BiFeO3 Superlattice
by Fardiman Ruli, Houssny Bouyanfif and Kyungwan Kim
Materials 2024, 17(6), 1405; https://doi.org/10.3390/ma17061405 - 19 Mar 2024
Viewed by 1455
Abstract
We investigated the ultrafast dynamics of a SrRuO3/BiFeO3 superlattice grown on a SrTiO3 substrate using a near infrared pump–probe technique at various temperatures. The superlattice exhibits a ferromagnetic order inherited from the SrRuO3 layer. The pump-induced changes in [...] Read more.
We investigated the ultrafast dynamics of a SrRuO3/BiFeO3 superlattice grown on a SrTiO3 substrate using a near infrared pump–probe technique at various temperatures. The superlattice exhibits a ferromagnetic order inherited from the SrRuO3 layer. The pump-induced changes in the reflectivity reveal periodic oscillations. We found that the oscillation frequency can be well explained by zone-folded acoustic phonon oscillations, whose dispersion depends on the sound velocity, density, and thickness within the supercell of each constituent layer. It is found that the observed oscillation frequency corresponds to the A1 mode, which suggests that oscillations are excited due to pump-induced expansion of the SrRuO3 layer that absorbs the pump photon. Temperature-dependent measurements reveal significant suppression of the oscillation amplitude in the ferromagnetic state. The suppressed amplitude is proportional to the square of the magnetization, M(T)2. This phenomenon can be attributed to a strong magnetostriction effect of SrRuO3 that suppresses lattice expansion upon pumping. Full article
(This article belongs to the Section Materials Physics)
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25 pages, 731 KiB  
Article
Jahn–Teller Magnets
by Alexander Moskvin
Magnetochemistry 2023, 9(11), 224; https://doi.org/10.3390/magnetochemistry9110224 - 2 Nov 2023
Cited by 3 | Viewed by 2671
Abstract
A wide class of materials with different crystal and electronic structures including quasi-2D unconventional superconductors, such as cuprates, nickelates, ferropnictides/chalcogenides, ruthenate Sr2RuO4, and 3D systems, such as manganites RMnO3, ferrates (CaSr)FeO3, nickelates RNiO3, [...] Read more.
A wide class of materials with different crystal and electronic structures including quasi-2D unconventional superconductors, such as cuprates, nickelates, ferropnictides/chalcogenides, ruthenate Sr2RuO4, and 3D systems, such as manganites RMnO3, ferrates (CaSr)FeO3, nickelates RNiO3, silver oxide AgO, are based on Jahn–Teller 3d and 4d ions. These unusual materials, called Jahn–Teller (JT) magnets, are characterized by an extremely rich variety of phase states, spanning from non-magnetic and magnetic insulators to unusual metallic and superconducting states. The unconventional properties of JT magnets can be attributed to the instability of their highly symmetric Jahn–Teller “progenitors” with the ground orbital E-state with repect to charge transfer, anti-Jahn–Teller d-d disproportionation, and the formation of a system of effective local composite spin–singlet or spin–triplet, electronic, or hole S-type bosons moving in a non-magnetic or magnetic lattice. We consider specific features of the anti-JT-disproportionation reaction, properties of the electron–hole dimers, possible phase states and effective Hamiltonians for single- and two-band JT magnets, concluding with a short overview of physical properties for actual JT magnets. Full article
(This article belongs to the Section Magnetic Materials)
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12 pages, 17002 KiB  
Article
Influence of Lattice Mismatch on Structural and Functional Properties of Epitaxial Ba0.7Sr0.3TiO3 Thin Films
by Jonas Wawra, Kornelius Nielsch and Ruben Hühne
Materials 2023, 16(17), 6036; https://doi.org/10.3390/ma16176036 - 2 Sep 2023
Cited by 5 | Viewed by 1966
Abstract
Substrate-induced strains can significantly influence the structural properties of epitaxial thin films. In ferroelectrics, this might lead to significant changes in the functional properties due to the strong electromechanical coupling in those materials. To study this in more detail, epitaxial Ba0.7Sr [...] Read more.
Substrate-induced strains can significantly influence the structural properties of epitaxial thin films. In ferroelectrics, this might lead to significant changes in the functional properties due to the strong electromechanical coupling in those materials. To study this in more detail, epitaxial Ba0.7Sr0.3TiO3 films, which have a perovskite structure and a structural phase transition close to room temperature, were grown with different thicknesses on REScO3 (RE–rare earth element) substrates having a smaller lattice mismatch compared to SrTiO3. A fully strained SrRuO3 bottom electrode and Pt top contacts were used to achieve a capacitor-like architecture. Different X-ray diffraction techniques were applied to study the microstructure of the films. Epitaxial films with a higher crystalline quality were obtained on scandates in comparison to SrTiO3, whereas the strain state of the functional layer was strongly dependent on the chosen substrate and the thickness. Differences in permittivity and a non-linear polarization behavior were observed at higher temperatures, suggesting that ferroelectricity is supressed under tensile strain conditions in contrast to compressive strain for our measurement configuration, while a similar reentrant relaxor-like behavior was found in all studied layers below 0°C. Full article
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15 pages, 3114 KiB  
Article
Nanoparticulate Perovskites for Photocatalytic Water Reduction
by Sven A. Freimann, Catherine E. Housecroft and Edwin C. Constable
Nanomaterials 2023, 13(14), 2094; https://doi.org/10.3390/nano13142094 - 18 Jul 2023
Viewed by 1473
Abstract
SrTiO3 and BaTiO3 nanoparticles (NPs) were activated using H2O2 or aqueous HNO3, and pristine and activated NPs were functionalized with a 2,2′-bipyridine phosphonic acid anchoring ligand (1), followed by reaction with RuCl3. [...] Read more.
SrTiO3 and BaTiO3 nanoparticles (NPs) were activated using H2O2 or aqueous HNO3, and pristine and activated NPs were functionalized with a 2,2′-bipyridine phosphonic acid anchoring ligand (1), followed by reaction with RuCl3.3H2O and bpy, RhCl3.3H2O and bpy, or RuCl3.3H2O. The surface-bound metal complex functionalized NPs were used for the photogeneration of H2 from water, and their activity was compared to related systems using TiO2 NPs. The role of pH during surface complexation was found to be important. The NPs were characterized using Fourier transform infrared (FTIR) and solid-state absorption spectroscopies, thermogravimetric analysis mass spectrometry (TGA-MS), and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), and the dihydrogen generation was analyzed using gas chromatography–mass spectrometry (GC-MS). Our findings indicate that extensively functionalized SrTiO3 or BaTiO3 NPs may perform better than TiO2 NPs for water reduction. Full article
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23 pages, 9877 KiB  
Review
The Progress on Magnetic Material Thin Films Prepared Using Polymer-Assisted Deposition
by Hongtao Ren, Jing Zhong and Gang Xiang
Molecules 2023, 28(13), 5004; https://doi.org/10.3390/molecules28135004 - 26 Jun 2023
Cited by 6 | Viewed by 2893
Abstract
Polymer-assisted deposition (PAD) has been widely used in the preparation of high-quality oxides and sulfides for basic research and applications. Specifically, diverse PAD-prepared magnetic material thin films such as ZnO, Ga2O3, SrRuO3, LaCoO3, LaMnO3 [...] Read more.
Polymer-assisted deposition (PAD) has been widely used in the preparation of high-quality oxides and sulfides for basic research and applications. Specifically, diverse PAD-prepared magnetic material thin films such as ZnO, Ga2O3, SrRuO3, LaCoO3, LaMnO3, Y3Fe5O12, MoS2, MoSe2, and ReS2 thin films have been grown, in which thickness-dependent, strain-modulated, doping-mediated, and/or morphology-dependent room-temperature ferromagnetism (RTFM) have been explored. Inspired by the discovery of intrinsic low-temperature FM in two-dimensional (2D) systems prepared using mechanical exfoliation, the search for more convenient methods to prepare 2D ferromagnetic materials with high-temperature FM has seen explosive growth, but with little success. Fortunately, the very recent synthesis of 2D NiO by PAD has shed light on this challenge. Based on these abovementioned developments, the difficulties of PAD when preparing a-few-nanometer single-crystalline materials and the opportunities in PAD for novel materials such as chiral magnetic soliton material Cr1/3NbS2 are discussed. Full article
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13 pages, 3560 KiB  
Article
Performance of Particulate and Structured Pt/TiO2-Based Catalysts for the WGS Reaction under Realistic High- and Low-Temperature Shift Conditions
by Andreas Kouroumlidis, Georgios Bampos, Paraskevi Panagiotopoulou and Dimitris I. Kondarides
Catalysts 2023, 13(2), 372; https://doi.org/10.3390/catal13020372 - 8 Feb 2023
Cited by 1 | Viewed by 2417
Abstract
The water–gas shift (WGS) activity of Pt/TiO2-based powdered and structured catalysts was investigated using realistic feed compositions that are relevant to the high-temperature shift (HTS) and low-temperature shift (LTS) reaction conditions. The promotion of the TiO2 support with small amounts [...] Read more.
The water–gas shift (WGS) activity of Pt/TiO2-based powdered and structured catalysts was investigated using realistic feed compositions that are relevant to the high-temperature shift (HTS) and low-temperature shift (LTS) reaction conditions. The promotion of the TiO2 support with small amounts of alkali- or alkaline earth-metals resulted in the enhancement of the WGS activity of 0.5%Pt/TiO2(X) catalysts (X = Na, Cs, Ca, Sr). The use of bimetallic (Pt–M)/TiO2 catalysts (M = Ru, Cr, Fe, Cu) can also shift the CO conversion curve toward lower temperatures, but this is accompanied by the production of relatively large amounts of unwanted CH4 at temperatures above ca. 300 °C. Among the powdered catalysts investigated, Pt/TiO2(Ca) exhibited the best performance under both HTS and LTS conditions. Therefore, this material was selected for the preparation of structured catalysts in the form of pellets as well as ceramic and metallic catalyst monoliths. The 0.5%Pt/TiO2(Ca) pellet catalyst exhibited comparable activity with that of a commercial WGS pellet catalyst, and its performance was further improved when the Pt loading was increased to 1.0 wt.%. Among the structured catalysts investigated, the best results were obtained for the sample coated on the metallic monolith, which exhibited excellent WGS performance in the 300–350 °C temperature range. In conclusion, proper selection of the catalyst structure and reaction parameters can shift the CO conversion curves toward sufficiently low temperatures, rendering the Pt/TiO2(Ca) catalyst suitable for practical applications. Full article
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20 pages, 4184 KiB  
Article
Topological Structure of the Order Parameter of Unconventional Superconductors Based on d- and f- Elements
by Victor G. Yarzhemsky and Egor A. Teplyakov
Symmetry 2023, 15(2), 376; https://doi.org/10.3390/sym15020376 - 31 Jan 2023
Cited by 2 | Viewed by 2711
Abstract
The superconducting order parameter (SOP) of a triplet superconductor UTe2 was constructed using the topological space group approach, in which, in contrast to phenomenological and topological approaches, the single pair function and phase winding in condensate are different quantities. The connection between [...] Read more.
The superconducting order parameter (SOP) of a triplet superconductor UTe2 was constructed using the topological space group approach, in which, in contrast to phenomenological and topological approaches, the single pair function and phase winding in condensate are different quantities. The connection between them is investigated for the D2h point group and the mmm magnetic group. It is shown how a non-unitary pair function of UTe2 can be constructed using one-dimensional real irreducible representations and Ginzburg–Landau phase winding. It is also shown that the total phase winding is non-zero in magnetic symmetry only. Experimental data on the superconducting order parameter of topological superconductors UPt3, Sr2RuO4, LaPt3P, and UTe2 are considered and peculiarities of their nodal structures are connected with the theoretical results of the topological space group approach. Full article
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9 pages, 1761 KiB  
Article
Dielectric and Antiferroelectric Properties of AgNbO3 Films Deposited on Different Electrodes
by Qingzhu Ma, Xiang Li, Yanle Zhang, Zhijin Duo, Suwei Zhang and Lei Zhao
Coatings 2022, 12(12), 1826; https://doi.org/10.3390/coatings12121826 - 25 Nov 2022
Cited by 3 | Viewed by 2255
Abstract
AgNbO3 antiferroelectric materials have become a hot topic due to their typical double polarization–electric field loops. AgNbO3 films usually exhibit superior properties to bulks. In this work, AgNbO3 films were fabricated via the pulsed laser deposition on (001) SrTiO3 [...] Read more.
AgNbO3 antiferroelectric materials have become a hot topic due to their typical double polarization–electric field loops. AgNbO3 films usually exhibit superior properties to bulks. In this work, AgNbO3 films were fabricated via the pulsed laser deposition on (001) SrTiO3 substrate with (La0.5Sr0.5)CoO3, LaNiO3 and SrRuO3 bottom electrodes, in which the (La0.5Sr0.5)CoO3, LaNiO3 and SrRuO3 bottom electrodes were used to regulate the in-plane compressive stress of AgNbO3 films. It is found that AgNbO3 films deposited on (La0.5Sr0.5)CoO3, LaNiO3 and SrRuO3 bottom electrodes are epitaxial with dense microstructure. In changing the bottom electrodes from (La0.5Sr0.5)CoO3, LaNiO3 to SrRuO3, the in-plane compressive stress of AgNbO3 thin films becomes weaker, which leads to increased relative dielectric permittivity and reduced antiferroelectric–ferroelectric phase transition electric field EF from 272 kV/cm to 190 kV/cm. The reduced EF implies weakened antiferroelectric stability in AgNbO3 films. It can be seen that the antiferroelectric stability of AgNbO3 films could be regulated by changing the bottom electrodes. Full article
(This article belongs to the Special Issue High-Performance Dielectric Ceramic for Energy Storage Capacitors)
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13 pages, 1813 KiB  
Article
Ferromagnetism and Superconductivity in CaRuO3/YBa2Cu3O7-δ Heterostructures
by Alina Marinela Ionescu, Ion Ivan, Claudiu Locovei, Melania Onea, Adrian Crisan, Soltan Soltan, Gisela Schütz and Joachim Albrecht
Materials 2022, 15(7), 2345; https://doi.org/10.3390/ma15072345 - 22 Mar 2022
Viewed by 3303
Abstract
The deposition of a ferromagnetic layer can affect the properties of high-temperature superconductors underneath. We investigated the influence of ferromagnetic CaRuO3 on the properties of YBa2Cu3O7-x (YBCO) superconducting thin films when the layers are either in direct [...] Read more.
The deposition of a ferromagnetic layer can affect the properties of high-temperature superconductors underneath. We investigated the influence of ferromagnetic CaRuO3 on the properties of YBa2Cu3O7-x (YBCO) superconducting thin films when the layers are either in direct contact or separated by a barrier layer of 5 nm SrTiO3. Detailed measurements of the magnetic moment of the superconductor and ferromagnet as a function of temperature and magnetic field have been performed using SQUID magnetometry. Magnetometry and relaxation measurements show that the modification of the superconducting properties of YBCO strongly depends on the interaction with the ferromagnetic layer on top. The barrier layer has a significant impact on both the supercon-ducting properties of the YBCO film and the ferromagnetic ordering of CaRuO3. The physical properties mentioned above were discussed in correlation with the materials’ structure determined by XRD analysis. Full article
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16 pages, 3378 KiB  
Review
A Review of Electronic Transport in Superconducting Sr2RuO4 Junctions
by Muhammad Shahbaz Anwar and Jason W. A. Robinson
Coatings 2021, 11(9), 1110; https://doi.org/10.3390/coatings11091110 - 14 Sep 2021
Cited by 5 | Viewed by 3849
Abstract
We review electronic transport in superconducting junctions with Sr2RuO4. Transport measurements provide evidence for chiral domain walls and, therefore, chiral superconductivity in superconducting Sr2RuO4, but so far, the symmetry of the underlying superconducting state remains [...] Read more.
We review electronic transport in superconducting junctions with Sr2RuO4. Transport measurements provide evidence for chiral domain walls and, therefore, chiral superconductivity in superconducting Sr2RuO4, but so far, the symmetry of the underlying superconducting state remains inconclusive. Further studies involving density of states measurements and spin-polarised transport in local/non-local Sr2RuO4 junctions with magnetic materials could lead to fundamental discoveries and a better understanding of the superconducting state. Full article
(This article belongs to the Special Issue Advances in Superconducting Films)
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20 pages, 13607 KiB  
Article
Assessment of Surface Water Quality in the Podu Iloaiei Dam Lake (North-Eastern Romania): Potential Implications for Aquaculture Activities in the Area
by Cornelia Amarandei, Alina-Giorgiana Negru, Laurentiu-Valentin Soroaga, Simona-Maria Cucu-Man, Romeo-Iulian Olariu and Cecilia Arsene
Water 2021, 13(17), 2395; https://doi.org/10.3390/w13172395 - 31 Aug 2021
Cited by 3 | Viewed by 3207
Abstract
The Podu Iloaiei Dam Lake located on the Bahluet River from Bahlui hydrographic basin, north-eastern Romania, is one of the most important water resources used for aquaculture activities in the region of interest. In the present study, the chemical composition related to water-soluble [...] Read more.
The Podu Iloaiei Dam Lake located on the Bahluet River from Bahlui hydrographic basin, north-eastern Romania, is one of the most important water resources used for aquaculture activities in the region of interest. In the present study, the chemical composition related to water-soluble ions and elements was assessed in both water and sediment samples collected from the area of interest during July 2017 and October 2017, representative months for warm and cold seasons, respectively. Water-soluble ions (H3C2O2, HCO2, C2O42−, F, Cl, NO2, Br, NO3, SO42−, Li+, Na+, NH4+, K+, and Ca2+) were analyzed by ion chromatography, while inductively coupled plasma mass spectrometry was used to quantify water-soluble fractions of elements (Be, B, Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Mo, Ru, Pd, Ag, Cd, Sn, Sb, Te, Ba, Ir, Tl, Pb, Bi, and U). Evidence was obtained on the contributions of both anthropogenic and natural (pedologic) related sources in controlling the chemical composition of the water and sediment samples in the area. Analysis of Piper diagrams revealed the existence of CO32−/HCO3 and Ca2+/Mg2+ as dominant species for the sediment samples. The interest water pool was found to be oligotrophic over the warm period and eutrophic over the cold period. Overall, abundances and the association of chemical species in the area seemed to be controlled by a complex interplay between the water body’s main characteristics, meteorological factors, and anthropogenic activities. Moreover, the present results suggest that precautions should be taken for physicochemical parameter monitoring and prevention acts for surface water quality assurance in order to control the potential negative influence of some chemical parameters on fish productivity. Reported data also have a high potential to be used by experts in the field of developing lake water management policies for a sustainable exploitation of various aquatic systems. Full article
(This article belongs to the Section Soil and Water)
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15 pages, 435 KiB  
Article
Multiplicity, Parity and Angular Momentum of a Cooper Pair in Unconventional Superconductors of D4h Symmetry: Sr2RuO4 and Fe-Pnictide Materials
by Victor G. Yarzhemsky
Symmetry 2021, 13(8), 1435; https://doi.org/10.3390/sym13081435 - 5 Aug 2021
Cited by 6 | Viewed by 2728
Abstract
Sr2RuO4 and Fe-pnictide superconductors belong to the same point group symmetry D4h. Many experimental data confirm odd pairs in Sr2RuO4 and even pairs in Fe-pnictides, but opposite conclusions also exist. Recent NMR results of [...] Read more.
Sr2RuO4 and Fe-pnictide superconductors belong to the same point group symmetry D4h. Many experimental data confirm odd pairs in Sr2RuO4 and even pairs in Fe-pnictides, but opposite conclusions also exist. Recent NMR results of Pustogow et al., which revealed even Cooper pairs in Sr2RuO4, require reconsideration of symmetry treatment of its SOP (superconducting order parameter). In the present work making use of the Mackey–Bradley theorem on symmetrized squares, a group theoretical investigation of possible pairing states in D4h symmetry is performed. It is obtained for I4/mmm , i.e., space group of Sr2RuO4, that triplet pairs with even spatial parts are possible in kz direction and in points M and Y. For the two latter cases pairing of equivalent electrons with nonzero total momentum is proposed. In P4/nmm space group of Fe- pnictides in point M, even and odd pairs are possible for singlet and triplet cases. It it shown that even and odd chiral states with angular momentum projection m=±1 have nodes in vertical planes, but Eg is nodal , whereas Eu is nodeless in the basal plane. It is also shown that the widely accepted assertion that the parity of angular momentum value is directly connected with the spatial parity of a pair is not valid in a space-group approach to the wavefunction of a Cooper pair. Full article
(This article belongs to the Special Issue Understanding Iron Superconductors and Isostructural Materials)
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