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16 pages, 6994 KiB

Open AccessArticle

Point-Contact Spectroscopy in Bulk Samples of Electron-Doped Cuprate Superconductors

by Angela Nigro, Anita Guarino, Antonio Leo, Gaia Grimaldi, Francesco Avitabile and Paola Romano

Materials 2023, 16(24), 7644; https://doi.org/10.3390/ma16247644 - 14 Dec 2023

Viewed by 777

Abstract

Point-contact spectroscopy was performed on bulk samples of electron-doped high temperature superconductor Nd_2−xCe_xCuO_4−δ. The samples were characterized using X-ray diffraction and scanning electron microscopy equipped with a wavelength-dispersive spectrometer and an electron backscatter diffraction detector. Samples with [...] Read more.

Point-contact spectroscopy was performed on bulk samples of electron-doped high temperature superconductor Nd_2−xCe_xCuO_4−δ. The samples were characterized using X-ray diffraction and scanning electron microscopy equipped with a wavelength-dispersive spectrometer and an electron backscatter diffraction detector. Samples with Ce content x = 0.15 showed the absence of spurious phases and randomly oriented grains, most of which had dimensions of approximately 220 µm². The low-bias spectra in the tunneling regime, i.e., high-transparency interface, exhibited a gap feature at about ±5 meV and no zero-bias conductance, despite the random oriented grains investigated within our bulk samples, consistent with most of the literature data on oriented samples. High-bias conductance was also measured in order to obtain information on the properties of the barrier. A V-shape was observed in some cases, instead of the parabolic behavior expected for tunnel junctions. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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13 pages, 3130 KiB

Open AccessArticle

Rough and Porous Micropebbles of CeCu₂Si₂ for Energy Storage Applications

by Davide Scarpa, Claudia Cirillo, Christopher Luciano, Angela Nigro, Renata Adami, Carla Cirillo, Carmine Attanasio, Mariagrazia Iuliano, Eleonora Ponticorvo and Maria Sarno

Materials 2023, 16(22), 7182; https://doi.org/10.3390/ma16227182 - 16 Nov 2023

Viewed by 634

Abstract

Supercapacitors have attracted considerable attention due to their advantages, including being lightweight and having rapid charge–discharge, a good rate capability, and high cyclic stability. Electrodes are one of the most important factors influencing the performance of supercapacitors. Herein, a three-dimensional network of rough [...] Read more.

Supercapacitors have attracted considerable attention due to their advantages, including being lightweight and having rapid charge–discharge, a good rate capability, and high cyclic stability. Electrodes are one of the most important factors influencing the performance of supercapacitors. Herein, a three-dimensional network of rough and porous micropebbles of CeCu₂Si₂ has been prepared using a one-step procedure and tested for the first time as a supercapacitor electrode. The synthesized material was extensively characterized in a three-electrode configuration using different electrochemical techniques, such as cyclic voltammetry (CV), galvanostatic charge and discharge (GCD) tests, and electrochemical impedance spectroscopy (EIS). CeCu₂Si₂ shows rather high mass-capacitance values: 278 F/g at 1 A/g and 295 F/g at 10 mV/s. Moreover, the material exhibits remarkable long-term stability: 98% of the initial capacitance was retained after 20,000 cycles at 10 A/g and the Coulombic efficiency remains equal to 100% at the end of the cycles. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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12 pages, 1620 KiB

Open AccessFeature PaperArticle

Axion Field Influence on Josephson Junction Quasipotential

by Roberto Grimaudo, Davide Valenti, Bernardo Spagnolo, Antonio Troisi, Giovanni Filatrella and Claudio Guarcello

Materials 2023, 16(17), 5972; https://doi.org/10.3390/ma16175972 - 31 Aug 2023

Cited by 1 | Viewed by 607

Abstract

The direct effect of an axion field on Josephson junctions is analyzed through the consequences on the effective potential barrier that prevents the junction from switching from the superconducting to the finite-voltage state. We describe a method to reliably compute the quasipotential with [...] Read more.

The direct effect of an axion field on Josephson junctions is analyzed through the consequences on the effective potential barrier that prevents the junction from switching from the superconducting to the finite-voltage state. We describe a method to reliably compute the quasipotential with stochastic simulations, which allows for the spanning of the coupling parameter from weakly interacting axion to tight interactions. As a result, we obtain an axion field that induces a change in the potential barrier, therefore determining a significant detectable effect for such a kind of elusive particle. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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10 pages, 2921 KiB

Open AccessEditor’s ChoiceArticle

Iron Selenide Particles for High-Performance Supercapacitors

by Davide Scarpa, Claudia Cirillo, Eleonora Ponticorvo, Carla Cirillo, Carmine Attanasio, Mariagrazia Iuliano and Maria Sarno

Materials 2023, 16(15), 5309; https://doi.org/10.3390/ma16155309 - 28 Jul 2023

Cited by 4 | Viewed by 912

Abstract

Nowadays, iron (II) selenide (FeSe), which has been widely studied for years to unveil the high-temperature superconductivity in iron-based superconductors, is drawing increasing attention in the electrical energy storage (EES) field as a supercapacitor electrode because of its many advantages. In this study, [...] Read more.

Nowadays, iron (II) selenide (FeSe), which has been widely studied for years to unveil the high-temperature superconductivity in iron-based superconductors, is drawing increasing attention in the electrical energy storage (EES) field as a supercapacitor electrode because of its many advantages. In this study, very small FeSe particles were synthesized via a simple, low-cost, easily scalable, and reproducible solvothermal method. The FeSe particles were characterized using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS), revealing enhanced electrochemical properties: a high capacitance of 280 F/g at 0.5 A/g, a rather high energy density of 39 Wh/kg and a corresponding power density of 306 W/kg at 0.5 A/g, an extremely high cycling stability (capacitance retention of 92% after 30,000 cycles at 1 A/g), and a rather low equivalent series resistance (R_ESR) of ~2 Ω. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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10 pages, 3033 KiB

Open AccessArticle

AC Loss in High-Temperature Superconducting Bulks Subjected to Alternating and Rotating Magnetic Fields

by Wafa Ali Soomro, Youguang Guo, Haiyan Lu, Jianxun Jin, Boyang Shen and Jianguo Zhu

Materials 2023, 16(2), 633; https://doi.org/10.3390/ma16020633 - 9 Jan 2023

Cited by 3 | Viewed by 1234

Abstract

High-temperature superconductor (HTS) bulks have demonstrated extremely intriguing potential for industrial and commercial applications due to their capability to trap significantly larger magnetic fields than conventional permanent magnets. The magnetic field in electrical rotating machines is a combination of alternating and rotational fields. [...] Read more.

High-temperature superconductor (HTS) bulks have demonstrated extremely intriguing potential for industrial and commercial applications due to their capability to trap significantly larger magnetic fields than conventional permanent magnets. The magnetic field in electrical rotating machines is a combination of alternating and rotational fields. In contrast, all previous research on the characterization of electromagnetic properties of HTS have solely engrossed on the alternating AC magnetic fields and the associated AC loss. This research paper gives a thorough examination of the AC loss measurement under various conditions. The obtained results are compared to the finite element-based H-formulation. The AC loss is measured at various amplitudes of circular flux density patterns and compared with the AC loss under one-dimensional alternating flux density. The loss variation has also been studied at other frequencies. The findings in this research paper provide more insights into material characterization, which will be useful in the design of future large-scale HTS applications. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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11 pages, 2290 KiB

Open AccessArticle

The Compliance of the Upper Critical Field in Magic-Angle Multilayer Graphene with the Pauli Limit

by Evgueni F. Talantsev

Materials 2023, 16(1), 256; https://doi.org/10.3390/ma16010256 - 27 Dec 2022

Cited by 2 | Viewed by 1132

Abstract

The Pauli limiting field represents a fundamental magnetic field at which the superconducting state collapses due to the spin-paramagnetic Cooper pair-breaking effect. Cao et al. (Nature 2021, 595, 526) reported that the magic-angle twisted trilayer graphene (MATNG, N = [...] Read more.

The Pauli limiting field represents a fundamental magnetic field at which the superconducting state collapses due to the spin-paramagnetic Cooper pair-breaking effect. Cao et al. (Nature 2021, 595, 526) reported that the magic-angle twisted trilayer graphene (MATNG, N = 3) exhibits the upper critical field which exceeds the Pauli limiting field by two to three times. This observation was interpreted as a violation of the Pauli-limiting field in MAT3G. Similar conclusions were recently reported by the same research group in MATNG (N = 4, 5) superlattices (Park, J.M. et al. Nat. Mater.2022, 21, 877). Here, we point out that Cao et al. (Nature 2021, 595, 526) calculated the Pauli limiting field by the use of reduced form (to the weak-coupling limit) of full equation of the theory of the electron–phonon-mediated superconductivity. Considering that in the same paper, Cao et al. (Nature 2021, 595, 526) reported that MATNGs are strong coupled superconductors, we calculate the Pauli limiting field for a strong coupled case and show that the observed upper critical fields in MATNGs comply with the Pauli limit. This implies that there is no violation of the Pauli limiting field in the Moiré multilayer graphene superlattices. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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8 pages, 2105 KiB

Open AccessArticle

High Critical Current Density in the Textured Nanofiber Structure in Multifilament MgB₂ Wires Made by the Powder-In-Tube (PIT) Technique

by Daniel Gajda, Andrzej J. Zaleski, Andrzej J. Morawski, Małgorzata Małecka, Lan Maria Tran, Matt Rindfleisch, Tomasz Durejko and Tomasz Czujko

Materials 2022, 15(15), 5419; https://doi.org/10.3390/ma15155419 - 5 Aug 2022

Viewed by 993

Abstract

We show that the structure of multifilament MgB₂ wires made by the powder-in-tube (PIT) method can be texturized by annealing the structure under high isostatic pressure. Our results show that we obtained continuous fibers with a uniform diameter of 250 nm in [...] Read more.

We show that the structure of multifilament MgB₂ wires made by the powder-in-tube (PIT) method can be texturized by annealing the structure under high isostatic pressure. Our results show that we obtained continuous fibers with a uniform diameter of 250 nm in all 36 filaments, a small grain size of approximately 50 nm and a high density of the superconducting material. These results contribute to a significant improvement in the critical current density in high magnetic fields, e.g., 100 A/mm² at 14 T and 4.2 K. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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8 pages, 1703 KiB

Open AccessArticle

Magnetic Instabilities in the Quasi-One-Dimensional K₂Cr₃As₃ Material with Twisted Triangular Tubes

by Armando Galluzzi, Giuseppe Cuono, Alfonso Romano, Jianlin Luo, Carmine Autieri, Canio Noce and Massimiliano Polichetti

Materials 2022, 15(6), 2292; https://doi.org/10.3390/ma15062292 - 20 Mar 2022

Cited by 4 | Viewed by 1473

Abstract

The magnetic response of a frustrated K₂Cr₃As₃ sample having triangular arrays of twisted tubes has been studied by means of dc magnetization measurements as a function of the magnetic field (H) at different temperatures ranging from [...] Read more.

The magnetic response of a frustrated K₂Cr₃As₃ sample having triangular arrays of twisted tubes has been studied by means of dc magnetization measurements as a function of the magnetic field (H) at different temperatures ranging from 5 K up to 300 K. Looking at the magnetic hysteresis loops m(H), a diamagnetic behavior of the sample was inferred at temperatures higher than 60 K, whereas at lower temperatures the sample showed a hysteresis loop compatible with the presence of ferrimagnetism. Moreover, spike-like magnetization jumps, both positive and negative, were observed in a narrow range of the magnetic field around 800 Oe, regardless of the temperature considered and they were compared with the theoretical predictions on frustrated systems. The field position of the magnetization jumps was studied at different temperatures, and their distribution can be described by a Lorentzian curve. The analogies between the expected features and the experimental observations suggest that the jumps could be attributed to the magnetic frustration arising from the twisted triangular tubes present in the crystal lattice of this compound. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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Review

Jump to: Research

20 pages, 9160 KiB

Open AccessEditor’s ChoiceReview

Review of Single Crystal Synthesis of 11 Iron-Based Superconductors

by Qiang Hou, Longfei Sun, Yue Sun and Zhixiang Shi

Materials 2023, 16(14), 4895; https://doi.org/10.3390/ma16144895 - 8 Jul 2023

Cited by 1 | Viewed by 1366

Abstract

The 11 system in the iron-based superconducting family has become one of the most extensively studied materials in the research of high-temperature superconductivity, due to their simple structure and rich physical properties. Many exotic properties, such as multiband electronic structure, electronic nematicity, topology [...] Read more.

The 11 system in the iron-based superconducting family has become one of the most extensively studied materials in the research of high-temperature superconductivity, due to their simple structure and rich physical properties. Many exotic properties, such as multiband electronic structure, electronic nematicity, topology and antiferromagnetic order, provide strong support for the theory of high-temperature superconductivity, and have been at the forefront of condensed matter physics in the past decade. One noteworthy aspect is that a high upper critical magnetic field, large critical current density and lower toxicity give the 11 system good application prospects. However, the research on 11 iron-based superconductors faces numerous obstacles, mainly stemming from the challenges associated with producing high-quality single crystals. Since the discovery of FeSe superconductivity in 2008, researchers have made significant progress in crystal growth, overcoming the hurdles that initially impeded their studies. Consequently, they have successfully established the complete phase diagrams of 11 iron-based superconductors, including FeSe_1−xTe_x, FeSe_1−xS_x and FeTe_1−xS_x. In this paper, we aim to provide a comprehensive summary of the preparation methods employed for 11 iron-based single crystals over the past decade. Specifically, we will focus on hydrothermal, chemical vapor transport (CVT), self-flux and annealing methods. Additionally, we will discuss the quality, size, and superconductivity properties exhibited by single crystals obtained through different preparation methods. By exploring these aspects, we can gain a better understanding of the advantages and limitations associated with each technique. High-quality single crystals serve as invaluable tools for advancing both the theoretical understanding and practical utilization of high-temperature superconductivity. Full article

(This article belongs to the Special Issue Physics and Application of Superconductivity)

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