Condensed Matter

32 pages, 10430 KiB

Open AccessArticle

New Scaling Laws for Pinning Force Density in Superconductors

by Evgueni F. Talantsev

Condens. Matter 2022, 7(4), 74; https://doi.org/10.3390/condmat7040074 - 13 Dec 2022

Cited by 3 | Viewed by 1868

Since the report by Fietz and Webb (Phys. Rev.1968, 178, 657–667), who considered the pinning force density,

\vec{F_{p}} = \vec{J_{c}} \times \vec{B}

(where J_c is the critical current density and B is applied [...] Read more.

Since the report by Fietz and Webb (Phys. Rev.1968, 178, 657–667), who considered the pinning force density,

\vec{F_{p}} = \vec{J_{c}} \times \vec{B}

(where J_c is the critical current density and B is applied magnetic flux density), in isotropic superconductors as a unique function of reduced magnetic field,

\frac{B}{B_{c 2}}

(where

B_{c 2}

is the upper critical field),

|\vec{F_{p}}|

has been scaled based on the

\frac{B}{B_{c 2}}

ratio, for which there is a widely used Kramer–Dew–Hughes scaling law of

|\vec{F_{p}} (B)| = F_{p, m a x} {(\frac{B}{B_{c 2}})}^{p} {(1 - \frac{B}{B_{c 2}})}^{q}

, where

F_{p, m a x}

,

B_{c 2}

, p, and q are free-fitting parameters. To describe

|\vec{F_{p}} (B)|

in high-temperature superconductors, the Kramer–Dew–Hughes scaling law has been modified by (a) an assumption of the angular dependence of all parameters and (b) by the replacement of the upper critical field, B_c2, by the irreversibility field, B_irr. Here, we note that

\vec{F_{p}}

is also a function of critical current density, and thus, the

|\vec{F_{p}} (J_{c})|

scaling law should exist. In an attempt to reveal this law, we considered the full

|\vec{F_{p}} (B, J_{c})|

function and reported that there are three distinctive characteristic ranges of

(\frac{B}{B_{c 2}}, \frac{J_{c}}{J_{c} (s f)})

(where

J_{c} (s f)

is the self-field critical current density) on which

|\vec{F_{p}} (B, J_{c})|

can be splatted. Several new scaling laws for

|\vec{F_{p}} (J_{c})|

were proposed and applied to MgB₂, NdFeAs(O,F), REBCO, (La,Y)H₁₀, and YH₆. The proposed scaling laws describe the in-field performance of superconductors at low and moderate magnetic fields, and thus, the primary niche for these laws is superconducting wires and tapes for cables, fault current limiters, and transformers. Full article

(This article belongs to the Section Superconductivity)

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13 pages, 447 KiB

Open AccessArticle

DC Transport and Magnetotransport Properties of the 2D Isotropic Metallic System with the Fermi Surface Reconstructed by the Charge Density Wave

by Barbara Keran, Petra Grozić, Anatoly M. Kadigrobov, Zoran Rukelj and Danko Radić

Condens. Matter 2022, 7(4), 73; https://doi.org/10.3390/condmat7040073 - 09 Dec 2022

Viewed by 1320

Abstract

We report the ground state stabilization and corresponding electrical transport and magnetotransport properties of a 2D metallic system with an isotropic Fermi surface reconstructed by a charge density wave. The onset of the charge density wave is a spontaneous process, stabilized by the [...] Read more.

We report the ground state stabilization and corresponding electrical transport and magnetotransport properties of a 2D metallic system with an isotropic Fermi surface reconstructed by a charge density wave. The onset of the charge density wave is a spontaneous process, stabilized by the condensation energy gain due to the self-consistent mechanism of topological reconstruction of the Fermi surface and opening of the pseudo-gap around it. We address the signature of the uni-axial reconstruction in terms of the measurable quantities, such as the intra-band transport properties, including the one-particle density of states, the total and effective concentration of electrons, and the Hall coefficient. Additionally, we analyze the magnetotransport properties of the system reconstructed by the bi-axial, checkerboard-like charge density wave, under conditions of magnetic breakdown. It manifests huge quantum oscillations in diagonal components of magnetoconductivity, while the Hall conductivity changes sign, varying the external magnetic field with a finite region of vanishing Hall coefficient in between. Full article

(This article belongs to the Special Issue Selected Papers from the International Conference on Quantum Materials and Technologies (ICQMT2022))

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16 pages, 2147 KiB

Open AccessReview

Progress and Perspectives of Spectroscopic Studies on Carbon K-Edge Using Novel Soft X-ray Pulsed Sources

by Zeinab Ebrahimpour, Marcello Coreno, Luca Giannessi, Massimo Ferrario, Augusto Marcelli, Federico Nguyen, Seyed Javad Rezvani, Francesco Stellato and Fabio Villa

Condens. Matter 2022, 7(4), 72; https://doi.org/10.3390/condmat7040072 - 06 Dec 2022

Cited by 2 | Viewed by 2009

Abstract

The development of novel coherent and brilliant sources, such as soft X-ray free electron laser (FEL) and high harmonic generation (HHG), enables new ultrafast analysis of the electronic and structural dynamics of a wide variety of materials. Soft X-ray FEL delivers high-brilliance beams [...] Read more.

The development of novel coherent and brilliant sources, such as soft X-ray free electron laser (FEL) and high harmonic generation (HHG), enables new ultrafast analysis of the electronic and structural dynamics of a wide variety of materials. Soft X-ray FEL delivers high-brilliance beams with a short pulse duration, high spatial coherence and photon energy tunability. In comparison with FELs, HHG X-ray sources are characterized by a wide spectral bandwidth and few- to sub-femtosecond pulses. The approach will lead to the time-resolved reconstruction of molecular dynamics, shedding light on different photochemical pathways. The high peak brilliance of soft X-ray FELs facilitates investigations in a nonlinear regime, while the broader spectral bandwidth of the HHG sources may provide the simultaneous probing of multiple components. Significant technical breakthroughs in these novel sources are under way to improve brilliance, pulse duration, and to control spectral bandwidth, spot size, and energy resolution. Therefore, in the next few years, the new generation of soft X-ray sources combined with novel experimental techniques, new detectors, and computing capabilities will allow for the study of several extremely fast dynamics, such as vibronic dynamics. In the present review, we discuss recent developments in experiments, performed with soft X-ray FELs and HHG sources, operating near the carbon K-absorption edge, being a key atomic component in biosystems and soft materials. Different spectroscopy methods such as time-resolved pump-probe techniques, nonlinear spectroscopies and photoelectron spectroscopy studies have been addressed in an attempt to better understand fundamental physico-chemical processes. Full article

(This article belongs to the Special Issue Experimental Ideas for Novel FEL Facilities Based on Plasma Acceleration)

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11 pages, 2953 KiB

Open AccessArticle

Structural and Electrochemical Behaviors of ZnO Structure: Effect of Different Zinc Precursor Molarity

by Ruziana Mohamed and Muhammad Syakir Azri Anuar

Condens. Matter 2022, 7(4), 71; https://doi.org/10.3390/condmat7040071 - 05 Dec 2022

Cited by 2 | Viewed by 1367

Abstract

This research synthesised zinc oxide (ZnO) structure by a hydrothermal method. ZnO samples were prepared using different molarities of zinc (Zn) precursor, ranging from 0.10 to 0.16 M. Structural and morphological properties were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). [...] Read more.

This research synthesised zinc oxide (ZnO) structure by a hydrothermal method. ZnO samples were prepared using different molarities of zinc (Zn) precursor, ranging from 0.10 to 0.16 M. Structural and morphological properties were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns show that all samples are prominently grown along the three diffraction peaks at (001), (002) and (101) planes. The ZnO sample with 0.16 M Zn precursor has the highest peak orientation along the (002) plane. The average crystallite sizes for the ZnO structure with 0.10, 0.12, 0.14 and 0.16 M precursor are 48, 51, 49 and 31 nm, respectively. ZnO sample prepared at 0.16 M has the smallest crystallite size and the lowest tensile strain. The SEM images show that the ZnO samples are randomly oriented with average diameters of 209, 325, 295 and 348 nm when using 0.10, 0.12, 0.14 and 0.16 M of the precursor, respectively. The electrochemical behaviour of the ZnO structure was determined through cyclic voltammetry (CV) measurement. In the CV curve, the calculated specific capacitance for the ZnO sample prepared at 0.16 M has the highest value of 3.87 Fg⁻¹. The ZnO sample prepared at 0.10 M has the lowest specific capacitance value of 2.11 Fg⁻¹. Therefore, changing the molarity of the Zn precursor could change the structural and electrochemical properties. ZnO sample prepared with 0.16 M of the precursor provides the optimal result. Full article

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20 pages, 5238 KiB

Open AccessArticle

Systematic Trends in Hybrid-DFT Computations of BaTiO₃/SrTiO₃, PbTiO₃/SrTiO₃ and PbZrO₃/SrZrO₃ (001) Hetero Structures

by Roberts I. Eglitis, Sergei Piskunov, Anatoli I. Popov, Juris Purans, Dmitry Bocharov and Ran Jia

Condens. Matter 2022, 7(4), 70; https://doi.org/10.3390/condmat7040070 - 29 Nov 2022

Cited by 11 | Viewed by 2038

Abstract

We performed predictive hybrid-DFT computations for PbTiO₃, BaTiO₃, SrTiO₃, PbZrO₃ and SrZrO₃ (001) surfaces, as well as their BaTiO₃/SrTiO₃, PbTiO₃/SrTiO₃ and PbZrO₃/SrZrO₃ (001) heterostructures. According [...] Read more.

We performed predictive hybrid-DFT computations for PbTiO₃, BaTiO₃, SrTiO₃, PbZrO₃ and SrZrO₃ (001) surfaces, as well as their BaTiO₃/SrTiO₃, PbTiO₃/SrTiO₃ and PbZrO₃/SrZrO₃ (001) heterostructures. According to our hybrid-DFT computations for BO₂ and AO-terminated ABO₃ solid (001) surfaces, in most cases, the upper layer ions relax inwards, whereas the second layer ions shift upwards. Our hybrid-DFT computed surface rumpling s for the BO₂-terminated ABO₃ perovskite (001) surfaces almost always is positive and is in a fair agreement with the available LEED and RHEED experiments. Computed B-O atom chemical bond population values in the ABO₃ perovskite bulk are enhanced on its BO₂-terminated (001) surfaces. Computed surface energies for BO₂ and AO-terminated ABO₃ perovskite (001) surfaces are comparable; thus, both (001) surface terminations may co-exist. Our computed ABO₃ perovskite bulk Γ-Γ band gaps are in fair agreement with available experimental data. BO₂ and AO-terminated (001) surface Γ-Γ band gaps are always reduced with regard to the respective bulk band gaps. For our computed BTO/STO and PTO/STO (001) interfaces, the average augmented upper-layer atom relaxation magnitudes increased by the number of augmented BTO or PTO (001) layers and always were stronger for TiO₂-terminated than for BaO or PbO-terminated upper layers. Our B3PW concluded that BTO/STO, as well as SZO/PZO (001) interface Γ-Γ band gaps, very strongly depends on the upper augmented layer BO₂ or AO-termination but considerably less so on the number of augmented (001) layers. Full article

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20 pages, 8483 KiB

Open AccessArticle

Physicochemical Properties of Ti³⁺ Self-Doped TiO₂ Loaded on Recycled Fly-Ash Based Zeolites for Degradation of Methyl Orange

by Iván Supelano García, Carlos Andrés Palacio Gómez, Marc H. Weber, Indry Milena Saavedra Gaona, Claudia Patricia Castañeda Martínez, José Jobanny Martínez Zambrano, Hugo Alfonso Rojas Sarmiento, Julian Andrés Munevar Cagigas, Marcos A. Avila, Carlos Rettori, Carlos Arturo Parra Vargas and Julieth Alexandra Mejía Gómez

Condens. Matter 2022, 7(4), 69; https://doi.org/10.3390/condmat7040069 - 18 Nov 2022

Cited by 2 | Viewed by 1790

Abstract

The extensive production of coal fly ash by coal combustion is an issue of concern due to its environmental impact. TiO₂-zeolite composites were synthesized, at low cost, using recycled coal fly ash from a local thermoelectric power plant to produce the [...] Read more.

The extensive production of coal fly ash by coal combustion is an issue of concern due to its environmental impact. TiO₂-zeolite composites were synthesized, at low cost, using recycled coal fly ash from a local thermoelectric power plant to produce the zeolite using the hydrothermal method. TiO₂ was loaded by means of the impregnation method using ethanol and titanium isopropoxide between 8.7 and 49.45 wt% TiO₂. The samples were characterized by X-ray diffraction, Raman, electron spin resonance, high-resolution transmission electron microscopy, N₂ adsorption-desorption, doppler broadening of annihilation radiation, and diffuse reflectance techniques, and the photocatalytic activity of the composites was evaluated according to the degradation of methyl orange under UV light. The results show that TiO₂ crystallizes in the anatase phase with a Ti³⁺ oxidation state, without post-treatment. TiO₂ particles were located within the pores of the substrate and on its surface, increasing the surface area of the composites in comparison with that of the substrates. Samples with TiO₂ at 8.7 and 25 wt% immobilized on hydroxysodalite show the highest degradation of methyl orange among all studied materials, including the commercial TiO₂ Degussa P25 under UV light. Full article

(This article belongs to the Special Issue New Advances in Condensed Matter Physics)

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12 pages, 6776 KiB

Open AccessArticle

Polarons in Rock-Forming Minerals: Physical Implications

by Boriana Mihailova, Giancarlo Della Ventura, Naemi Waeselmann, Simone Bernardini, Wei Xu and Augusto Marcelli

Condens. Matter 2022, 7(4), 68; https://doi.org/10.3390/condmat7040068 - 16 Nov 2022

Cited by 3 | Viewed by 1512

Abstract

The existence of thermally-activated quasiparticles in amphiboles is an important issue, as amphiboles are among the main hydrous complex silicate minerals in the Earth’s lithosphere. The amphibole structure consists of stripes of 6-membered TO₄-rings sandwiching MO₆ octahedral slabs. To elucidate [...] Read more.

The existence of thermally-activated quasiparticles in amphiboles is an important issue, as amphiboles are among the main hydrous complex silicate minerals in the Earth’s lithosphere. The amphibole structure consists of stripes of 6-membered TO₄-rings sandwiching MO₆ octahedral slabs. To elucidate the atomistic origin of the anomalous rock conductivity in subduction-wedge regions, we studied several Fe-containing amphiboles with diverse chemistry by using in situ, temperature-dependent, polarised Raman spectroscopy. The occurrence of resonance Raman scattering at high temperatures unambiguously reveal temperature-activated small polarons arising from the coupling between polar optical phonons and electron transitions within Fe²⁺O₆ octahedra, independently of the amphibole chemical composition. The FeO₆-related polarons coexist with delocalised H⁺; that is, at elevated temperatures Fe-bearing amphiboles are conductive and exhibit two types of charge carriers: electronic polarons with highly anisotropic mobility and H⁺ cations. The results from density-functional-theory calculations on the electron band structure for a selected amphibole compound with a relatively simple composition are in full agreement with experimental data. The polaron activation temperature, mobility, and polaron-dipole magnitude and alignment can be controlled by varying the mineral composition, which makes amphiboles attractive “geo-stripes” that can serve as mineral-inspired technology to design thermally-stable smart materials with anisotropic properties. Full article

(This article belongs to the Special Issue Superstripes Physics)

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6 pages, 1358 KiB

Open AccessCommunication

Substrate Effect on the Thermal Expansion of 2D Materials: An Investigation by Machine Learning Interatomic Potentials

by Ali Rajabpour and Bohayra Mortazavi

Condens. Matter 2022, 7(4), 67; https://doi.org/10.3390/condmat7040067 - 15 Nov 2022

Cited by 1 | Viewed by 1556

Abstract

The thermal expansion coefficient (TEC) of suspended two-dimensional (2D) nanomaterials is usually negative due to their ability for large out-of-plane deflection as the temperature increases. The presence of a substrate can nonetheless restrict the flexibility of 2D materials and significantly change their dimensional [...] Read more.

The thermal expansion coefficient (TEC) of suspended two-dimensional (2D) nanomaterials is usually negative due to their ability for large out-of-plane deflection as the temperature increases. The presence of a substrate can nonetheless restrict the flexibility of 2D materials and significantly change their dimensional change by temperature. In this short communication, the thermal expansion coefficients of suspended and supported four popular 2D structures of graphene, phagraphene, C₃N and BC₃ monolayers is systematically investigated. For this purpose, we conduct molecular dynamics simulation, in which the atomic interactions are defined by highly accurate machine learning interatomic potentials. The obtained results show that by increasing the strength of the van der Waals interactions between the monolayer and the substrate, from 2 meV to 8 meV, the TEC for graphene and phagraphene increases from a negative value to a positive one; while the negative value for the C₃N and BC₃ structures is still retained. Analysis of molecular dynamics trajectories reveals that the substrate can significantly reduce the formation of out-of-plane wrinkles and consequently affect the value of TEC. The obtained results provide useful vision on the role of substrate on the complex thermal expansion responses of 2D materials. Full article

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19 pages, 8510 KiB

Open AccessArticle

Elucidation of Structures, Electronic Properties, and Chemical Bonding of Monophosphorus-Substituted Boron Clusters in Neutral, Negative, and Positively Charged PB_n/

{P B}_{n}^{-}

/

{P B}_{n}^{+}

(n = 4–8)

by Qing-Shan Li, Bingyi Song, Limei Wen, Li-Ming Yang and Eric Ganz

Condens. Matter 2022, 7(4), 66; https://doi.org/10.3390/condmat7040066 - 12 Nov 2022

Viewed by 1516

Abstract

This paper reports the computational study of phosphorus-doped boron clusters PB_n/

{P B}_{n}^{-}

/

{P B}_{n}^{+}

(n = 4–8). First, a global search and optimization of these clusters were performed to determine the stable structures. We used [...] Read more.

This paper reports the computational study of phosphorus-doped boron clusters PB_n/

{P B}_{n}^{-}

/

{P B}_{n}^{+}

(n = 4–8). First, a global search and optimization of these clusters were performed to determine the stable structures. We used density functional theory (DFT) methods and ab initio calculations to study the stability of the atomic clusters and to explore the arrangement of stable structures. We found that the lowest energy structures of the smaller phosphorus-doped boron clusters tend to form planar or quasi-planar structures. As additional boron atoms are added to the smallest structures, the boron atoms expand in a zigzag arrangement or in a net-like manner, and the phosphorus atom is arranged on the periphery. For larger structures with seven or eight boron atoms, an unusual umbrella-like structure appears. We calculated the binding energy as well as other energies to study cluster stability. We calculated the ionization energy, electron affinity, and the HOMO–LUMO gaps. In addition, we used the adaptive natural density partitioning program to perform bond analysis so that we have a comprehensive understanding of the bonding. In order to have a suitable connection with the experiment, we simulated the infrared and photoelectron spectra. Full article

(This article belongs to the Special Issue Feature Papers from Condensed Matter Editorial Board Members)

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10 pages, 1222 KiB

Open AccessArticle

Fermi-Liquid Nonadiabatic Highly Compressed Cesium Iodide Superconductor

by Evgueni F. Talantsev

Condens. Matter 2022, 7(4), 65; https://doi.org/10.3390/condmat7040065 - 11 Nov 2022

Cited by 2 | Viewed by 1573

Abstract

The experimental discovery that compressed sulfur hydride exhibits superconducting transition temperature of

T_{c} = 203 K

by Drozdov et al. (Nature 2015, 525, 73–76) sparked studies of compressed hydrides. This discovery was not a straightforward experimental examination [...] Read more.

The experimental discovery that compressed sulfur hydride exhibits superconducting transition temperature of

T_{c} = 203 K

by Drozdov et al. (Nature 2015, 525, 73–76) sparked studies of compressed hydrides. This discovery was not a straightforward experimental examination of a theoretically predicted phase, but instead it was a nearly five-decade-long experimental quest for superconductivity in highly compressed matters, varying from pure elements (hydrogen, oxygen, sulfur), hydrides (SiH₄, AlH₃) to semiconductors and ionic salts. One of these salts was cesium iodide, CsI, which exhibits the transition temperature of

T_{c} ≅ 1.5 K

at

P = 206 G P a

(Eremets et al., Science 1998, 281, 1333–1335). Detailed first principles calculations (Xu et al., Phys Rev B 2009, 79, 144110) showed that CsI should exhibit

T_{c} ~ 0.03 K

(

P = 180 GPa

). In an attempt to understand the nature of this discrepancy between the theory and the experiment, we analyzed the temperature-dependent resistance in compressed CsI and found that this compound is a perfect Fermi liquid metal which exhibits an extremely high ratio of Debye energy to Fermi energy,

\frac{ℏ ω_{D}}{k_{B} T_{F}} ≅ 17

. This implies that direct use of the Migdal–Eliashberg theory of superconductivity to calculate the transition temperature in CsI is incorrect, because the theory is valid for

\frac{ℏ ω_{D}}{k_{B} T_{F}} ≪ 1

. We also showed that CsI falls into the unconventional superconductors band in the Uemura plot. Full article

(This article belongs to the Section Superconductivity)

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4 pages, 354 KiB

Open AccessArticle

Simple Explanation of Cuprates Linear Magnetoresistance Enigma

by Victor D. Lakhno

Condens. Matter 2022, 7(4), 64; https://doi.org/10.3390/condmat7040064 - 11 Nov 2022

Cited by 3 | Viewed by 1430

Abstract

A simple explanation is given for the linear dependence of electrical resistance on temperature and the linear dependence of the magnetoresistance on the magnetic field in high-temperature superconducting cuprates, which has been mysterious for many years. It is shown that this dependence stems [...] Read more.

A simple explanation is given for the linear dependence of electrical resistance on temperature and the linear dependence of the magnetoresistance on the magnetic field in high-temperature superconducting cuprates, which has been mysterious for many years. It is shown that this dependence stems from the treatment of a gas of translationally invariant polarons as a system with heavy fermions for wave vectors close to nesting. The destruction of such polarons at finite temperature and an external magnetic field leads to a linear dependence of the magnetoresistance on the magnetic field and temperature. It is shown that the relationship between the slopes of the magnetoresistance curves at zero magnetic field and at zero temperature is determined by the universal ratio

k_{B} / μ_{B}

in fermion systems and

k_{B} / 2 μ_{B}

in boson systems, where

k_{B}

is the Boltzmann constant and

μ_{B}

is the Bohr magneton. A relation between the existence of translationally invariant polarons and the “Planck” time of their relaxation is discussed. Full article

(This article belongs to the Section Superconductivity)

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11 pages, 1796 KiB

Open AccessArticle

Analysis of Structural, Optical, and Magnetic Properties of (Fe,Co) Co-Doped ZnO Nanoparticles Synthesized under UV Light

by Nawal Madkhali

Condens. Matter 2022, 7(4), 63; https://doi.org/10.3390/condmat7040063 - 08 Nov 2022

Cited by 3 | Viewed by 1617

Abstract

In this report, we discuss the preparation of undoped and (Fe,Co) co-doped ZnO nanocomposites via an ultrasonicated probe, which were both under UV irradiation for 12 h and annealed at 400 °C for four hours in ambient air. Here, we investigated the different [...] Read more.

In this report, we discuss the preparation of undoped and (Fe,Co) co-doped ZnO nanocomposites via an ultrasonicated probe, which were both under UV irradiation for 12 h and annealed at 400 °C for four hours in ambient air. Here, we investigated the different concentration of dopant transition metals (ZnO-Fe_1-x-Co_x) (x = 0.03, 0.05, and 0.07). X-ray diffraction (XRD) analyses confirmed the nanophase, crystallinity, good uniformity, and around 28 nm core sizes of all of the (ZnO-Fe_1-x-Co_x) as-synthesized composites with different rates. The optical properties of ZnO doped with a high percent of Fe nanoparticles displayed an increase in absorption in the UV region and a slight decrease in the energy band gap to 3.13 eV. Magnetic measurements revealed that doping enhanced the ferromagnetism of ZnO. Recent studies which aimed to improve the optical and magnetic properties of metal oxides, the most important of which being zinc oxide, have allowed their applications to diversify and multiply in the medical, industrial, and electronic fields. Full article

(This article belongs to the Special Issue Advances in Nanocomposite Materials)

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17 pages, 791 KiB

Open AccessArticle

Thermal and Quantum Fluctuation Effects on Non-Spherical Nuclei: The Case of Spin-1 System

by Mohammed Mahmud, Mulugeta Bekele and Yigermal Bassie

Condens. Matter 2022, 7(4), 62; https://doi.org/10.3390/condmat7040062 - 03 Nov 2022

Viewed by 1199

Abstract

In this work, we investigate the collective role of thermal and quantum fluctuations on non-equilibrium thermodynamics of a quantum system, specifically, the quantum-thermodynamic description of spin-1 nuclei based on the concepts of quantum and statistical mechanics. We explore the dynamical response of the [...] Read more.

In this work, we investigate the collective role of thermal and quantum fluctuations on non-equilibrium thermodynamics of a quantum system, specifically, the quantum-thermodynamic description of spin-1 nuclei based on the concepts of quantum and statistical mechanics. We explore the dynamical response of the system when driven out of equilibrium by a work parameter and compute analytically the full distribution of the work generated by the process. Considering work performed on the system as a random variable, we collect data for a large number of repeated cyclic processes of finite time. These data of finite time non-equilibrium processes will permit us to derive equilibrium values in quantities such as the free energy difference between the final and initial states of the system. Various properties of the system’s work distribution are explored. Full article

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14 pages, 2574 KiB

Open AccessArticle

Thermodynamic Functions of a Metal Exposed to High Energy Densities in Compressed and Expanded States

by Nikolay B. Volkov and Alexander I. Lipchak

Condens. Matter 2022, 7(4), 61; https://doi.org/10.3390/condmat7040061 - 27 Oct 2022

Cited by 1 | Viewed by 1421

Abstract

The development of a wide-range phenomenological model of metal with a small number of adjustable parameters for studying the behavior of metals in expanded and compressed states under the exposition of high energy density fluxes is the objective of the paper present. Both [...] Read more.

The development of a wide-range phenomenological model of metal with a small number of adjustable parameters for studying the behavior of metals in expanded and compressed states under the exposition of high energy density fluxes is the objective of the paper present. Both the reference data, methods of the quantum-statistical model of the atom, the density functional theory, and the requirement to the expanded and compressed states description of metal should be consistent on their boundary were used in the model. The expressions for thermodynamic functions and the critical parameters of expanded iron were obtained within the framework of the soft sphere model. The Grüneisen parameters calculated for the expanded and compressed states of the metal appear to be in good agreement with each other was shown. A calculation technique of the ion component average charge of the metal in expanded and compressed states is proposed. The experimentally defined volume range of V/V₀ = 3–4 in which the character of iron conductivity changes from metallic to non-metallic includes the obtained in frameworks of our approach value of the critical volume: V/V₀ = 3.802 was established. The behavior of the average charge of the ion component is discussed. The contribution of the thermal electrons to the thermodynamic functions is evaluated. Full article

(This article belongs to the Topic Applications of Photonics, Laser, Plasma and Radiation Physics)

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8 pages, 316 KiB

Open AccessArticle

Breakdown of Adiabatic Superconductivity in Ca-Doped h-BN Monolayer

by Ewa A. Drzazga-Szczȩśniak, Dominik Szczȩśniak, Adam Z. Kaczmarek and Radosław Szczȩśniak

Condens. Matter 2022, 7(4), 60; https://doi.org/10.3390/condmat7040060 - 26 Oct 2022

Cited by 1 | Viewed by 1202

Abstract

In the present paper, we report the breakdown of the adiabatic picture of superconductivity in a calcium-doped hexagonal boron nitride (Ca-h-BN) monolayer and discuss its implications for the selected properties of this phase. In particular, it is shown that the shallow [...] Read more.

In the present paper, we report the breakdown of the adiabatic picture of superconductivity in a calcium-doped hexagonal boron nitride (Ca-h-BN) monolayer and discuss its implications for the selected properties of this phase. In particular, it is shown that the shallow conduction band of the Ca-h-BN superconductor potentially cause a violation of the adiabatic Migdal’s theorem. As a result, the pivotal parameters that describe the superconducting state in Ca-h-BN are found to be notably influenced by the non-adiabatic effects. This finding is described here within the vertex-corrected Eliashberg formalism that predicts a strong reduction of the order parameter, superconducting transition temperature and superconducting gap in comparison to the estimates obtained in the framework of the adiabatic theory. The observed trends are in agreement with the recent results on superconductivity in hexagonal monolayers and confirm that the non-adiabatic effects have to be taken into account during the design of such future low-dimensional superconductors. Full article

(This article belongs to the Section Superconductivity)

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12 pages, 328 KiB

Open AccessArticle

Rabi Coupled Fermions in the BCS–BEC Crossover

by Luca Dell’Anna, Federico De Bettin and Luca Salasnich

Condens. Matter 2022, 7(4), 59; https://doi.org/10.3390/condmat7040059 - 22 Oct 2022

Viewed by 1228

Abstract

We investigate the three-dimensional BCS–BEC crossover in the presence of a Rabi coupling, which strongly affects several properties of the system, such as the chemical potential, the pairing gap and the superfluid density. We determine the critical interaction strength, below which the system [...] Read more.

We investigate the three-dimensional BCS–BEC crossover in the presence of a Rabi coupling, which strongly affects several properties of the system, such as the chemical potential, the pairing gap and the superfluid density. We determine the critical interaction strength, below which the system is normal also at zero temperature. Finally, we calculate the effect of the Rabi coupling on the critical temperature of the superfluid-to-normal phase transition by using different theoretical schemes. Full article

(This article belongs to the Special Issue Fluctuations and Highly Non-linear Phenomena in Superfluids and Superconductors VII)

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9 pages, 3405 KiB

Open AccessArticle

Anomalous Ca Content Dependence of Dielectric Properties of Charge-Ordered Pr_1−xCa_xMnO₃ as a Signature of Charge-Ordered Phase Modulation

by Ankit Kumar Singh and Partha Sarathi Mondal

Condens. Matter 2022, 7(4), 58; https://doi.org/10.3390/condmat7040058 - 21 Oct 2022

Viewed by 988

Abstract

Low-temperature dielectric properties of charge/orbital-ordered manganite, Pr_1−xCa_xMnO₃ for 0.40 ≤ x ≤ 0.50, was investigated systematically as a function of Ca content, x. The Ca content dependence of dielectric permittivity and dissipation factor exhibited distinct maxima [...] Read more.

Low-temperature dielectric properties of charge/orbital-ordered manganite, Pr_1−xCa_xMnO₃ for 0.40 ≤ x ≤ 0.50, was investigated systematically as a function of Ca content, x. The Ca content dependence of dielectric permittivity and dissipation factor exhibited distinct maxima near x~0.45. The overall dielectric response of charge-ordered Pr_1−xCa_xMnO₃ was dominated by dielectric polarization induced by polaron hopping and exhibited thermally activated relaxation behaviour. The thermally activated dielectric relaxation behaviour over the investigated temperature range was further analysed with the help of two models: the small polaron hopping model and the Mott three-dimensional variable range hopping model. The estimated polaron transport parameters also displayed non-monotonic variation with x and exhibited a broad minima between x = 0.425 and 0.45. Considering the previous work reported so far, the charge order pattern of Pr_1−xCa_xMnO₃ below x = 0.425 was most likely to be of Zener-polaron type, while near x = 0.50 was checker-board type and for in-between compositions; neither pure checker-board type nor pure Zener-polaron type can be considered a ground state. The observed results suggest that a modulation of the checkerboard-type charge/orbital ordering pattern in Pr_1−xCa_xMnO₃ possibly takes place in the Ca content range of investigation, 0.40 ≤ x ≤ 0.50. Full article

(This article belongs to the Section Physics of Materials)

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12 pages, 10373 KiB

Open AccessArticle

Magnetic Interaction in Doped 2D Perovskite Cuprates with Nanoscale Inhomogeneity: Lattice Nonlocal Effects vs. Superexchange

by Vladimir A. Gavrichkov and Semyon I. Polukeev

Condens. Matter 2022, 7(4), 57; https://doi.org/10.3390/condmat7040057 - 18 Oct 2022

Cited by 3 | Viewed by 1523

Abstract

We have studied the superexchange interaction

J_{i j}

in doped

2 D

cuprates. The AFM interaction strongly depends on the state of the lattice of a CuO

_{2}

layer surrounded by two LaO rock salt layers. In a static U and D [...] Read more.

We have studied the superexchange interaction

J_{i j}

in doped

2 D

cuprates. The AFM interaction strongly depends on the state of the lattice of a CuO

_{2}

layer surrounded by two LaO rock salt layers. In a static U and D stripe nanostructure, the homogeneous AFM interaction is impossible due to the

U / D / U \dots

periodic stripe sequence and

T_{N} = 0

. In a dynamic stripe nanostructure, the ideal CuO

_{2}

layer with nonlocal effects and the homogeneous AFM interaction are restored. However, the interaction

J_{i j}

decreases by the exponential factor due to partial dynamic quenching. The meaning of the transition from the dynamic to the static cases lies in the spontaneous

θ

-symmetry breaking with respect to the rotation of all the tilted CuO

_{6}

octahedra by an orientation angle

δ θ = n \cdot (45^{°})

(where

n = 1 \div 4

) in the U and D stripe nanostructure of the CuO

_{2}

layer. Moreover, the structural features help to study various experimental data on the charge inhomogeneity, Fermi level pinning in the p type cuprates only and time reversal symmetry breaking from a unified point of view. Full article

(This article belongs to the Special Issue Superstripes Physics)

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10 pages, 1650 KiB

Open AccessArticle

Scale-Free Distribution of Oxygen Interstitial Wires in Optimum-Doped HgBa₂CuO_4+y

by Gaetano Campi, Maria Vittoria Mazziotti, Thomas Jarlborg and Antonio Bianconi

Condens. Matter 2022, 7(4), 56; https://doi.org/10.3390/condmat7040056 - 12 Oct 2022

Cited by 1 | Viewed by 1532

Abstract

Novel nanoscale probes are opening new venues for understanding unconventional electronic and magnetic functionalities driven by multiscale lattice complexity in doped high-temperature superconducting perovskites. In this work, we focus on the multiscale texture at supramolecular level of oxygen interstitial (O-i) atomic stripes in [...] Read more.

Novel nanoscale probes are opening new venues for understanding unconventional electronic and magnetic functionalities driven by multiscale lattice complexity in doped high-temperature superconducting perovskites. In this work, we focus on the multiscale texture at supramolecular level of oxygen interstitial (O-i) atomic stripes in HgBa₂CuO_4+y at optimal doping for the highest superconducting critical temperature (T_C) of 94 K. We report compelling evidence for the nematic phase of oxygen interstitial O-i atomic wires with fractal-like spatial distribution over multiple scales using scanning micro- and nano-X-ray diffraction. The scale-free distribution of O-i atomic wires at optimum doping extending from the micron down to the nanoscale has been associated with the intricate filamentary network of hole-rich metallic wires in the CuO₂ plane. The observed critical opalescence provides evidence for the proximity to a critical point that controls the emergence of high-temperature superconductivity at optimum doping. Full article

(This article belongs to the Special Issue Superstripes Physics)

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9 pages, 1603 KiB

Open AccessArticle

Laser-Induced Magnetization Dynamics in Si-Doped Yttrium-Iron Garnet Film

by Mikhail Gaponov, Sergey Ovcharenko, Nikita Ilyin and Elena Mishina

Condens. Matter 2022, 7(4), 55; https://doi.org/10.3390/condmat7040055 - 08 Oct 2022

Cited by 1 | Viewed by 1471

Abstract

We experimentally demonstrate that the excitation of a silicon-doped yttrium-iron garnet film by femtosecond laser pulses triggers a magnetization precession with an amplitude determined by the external magnetization direction. The maximum efficiency is achieved at the pump wavelength corresponding to the absorption maximum [...] Read more.

We experimentally demonstrate that the excitation of a silicon-doped yttrium-iron garnet film by femtosecond laser pulses triggers a magnetization precession with an amplitude determined by the external magnetization direction. The maximum efficiency is achieved at the pump wavelength corresponding to the absorption maximum due to doping with silicon ions. Based on the azimuthal dependences of the precession amplitude and frequency, it is shown that the magnetization dynamics is induced by a thermal disruption of the magnetocrystalline anisotropy. By modeling hysteresis loops, it was found that the silicon doping leads to a decrease in the value of the exchange interaction in the film and an increase in the anisotropy field. Full article

(This article belongs to the Section Magnetism)

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9 pages, 820 KiB

Open AccessArticle

First Principles Calculations of the Optical Response of LiNiO₂

by Veenavee Nipunika Kothalawala, Assa Aravindh Sasikala Devi, Johannes Nokelainen, Matti Alatalo, Bernardo Barbiellini, Tao Hu, Ulla Lassi, Kosuke Suzuki, Hiroshi Sakurai and Arun Bansil

Condens. Matter 2022, 7(4), 54; https://doi.org/10.3390/condmat7040054 - 26 Sep 2022

Cited by 4 | Viewed by 2620

Abstract

We discuss optical properties of layered Lithium Nickel oxide (LiNiO

_{2}

), which is an attractive cathode material for realizing cobalt-free lithium-ion batteries, within the first-principles density functional theory (DFT) framework. Exchange correlation effects are treated using the generalized gradient approximation (GGA) and [...] Read more.

We discuss optical properties of layered Lithium Nickel oxide (LiNiO

_{2}

), which is an attractive cathode material for realizing cobalt-free lithium-ion batteries, within the first-principles density functional theory (DFT) framework. Exchange correlation effects are treated using the generalized gradient approximation (GGA) and the strongly-constrained-and-appropriately-normed (SCAN) meta-GGA schemes. A Hubbard parameter (U) is used to model Coulomb correlation effects on Ni 3d electrons. The GGA+U is shown to correctly predict an indirect (system wide) band gap of 0.46 eV in LiNiO

_{2}

, while the GGA yields a bandgap of only 0.08 eV. The calculated refractive index and its energy dependence is found to be in good agreement with the corresponding experimental results. Finally, our computed optical energy loss function yields insight into the results of recent RIXS experiments on LiNiO

_{2}

. Full article

(This article belongs to the Special Issue Rechargeable Batteries Studied Using Advanced Spectroscopic and Computational Techniques II)

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Condens. Matter, Volume 7, Issue 4 (December 2022) – 21 articles

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