Materials

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11 pages, 938 KiB

Open AccessArticle

Pressure-Induced Exciton Formation and Superconductivity in Platinum-Based Mineral Sperrylite

by Limin Wang, Rongwei Hu, Yash Anand, Shanta R. Saha, Jason R. Jeffries and Johnpierre Paglione

Materials 2024, 17(14), 3476; https://doi.org/10.3390/ma17143476 - 13 Jul 2024

Viewed by 509

Abstract

We report a comprehensive study of Sperrylite (PtAs₂), the main platinum source in natural minerals, as a function of applied pressures up to 150 GPa. While no structural phase transition is detected from pressure-dependent X-ray measurements, the unit cell volume shrinks [...] Read more.

We report a comprehensive study of Sperrylite (PtAs₂), the main platinum source in natural minerals, as a function of applied pressures up to 150 GPa. While no structural phase transition is detected from pressure-dependent X-ray measurements, the unit cell volume shrinks monotonically with pressure following the third-order Birch–Murnaghan equation of state. The mildly semiconducting behavior found in pure synthesized crystals at ambient pressures becomes more insulating upon increasing the applied pressure before metalizing at higher pressures, giving way to the appearance of an abrupt decrease in resistance near 3 K at pressures above 92 GPa consistent with the onset of a superconducing phase. The pressure evolution of the calculated electronic band structure reveals the same physical trend as our transport measurements, with a non-monotonic evolution explained by a hole band that is pushed below the Fermi energy and an electron band that approaches it as a function of pressure, both reaching a touching point suggestive of an excitonic state. A Lifshitz transition of the electronic structure and an increase in the density of states may naturally explain the onset of superconductivity in this material. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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11 pages, 1875 KiB

Open AccessCommunication

The Quest for High-Temperature Superconductivity in Nickelates under Ambient Pressure

by Leena Aggarwal and Ivan Božović

Materials 2024, 17(11), 2546; https://doi.org/10.3390/ma17112546 - 25 May 2024

Viewed by 915

Abstract

Recently, superconductivity with T_c ≈ 80 K was discovered in La₃Ni₂O₇ under extreme hydrostatic pressure (>14 GPa). For practical applications, we needed to stabilize this state at ambient pressure. It was proposed that this could be accomplished [...] Read more.

Recently, superconductivity with T_c ≈ 80 K was discovered in La₃Ni₂O₇ under extreme hydrostatic pressure (>14 GPa). For practical applications, we needed to stabilize this state at ambient pressure. It was proposed that this could be accomplished by substituting La with Ba. To put this hypothesis to the test, we used the state-of-the-art atomic-layer-by-layer molecular beam epitaxy (ALL-MBE) technique to synthesize (La_1−xBa_x)₃Ni₂O₇ films, varying x and the distribution of La (lanthanum) and Ba (barium). Regrettably, none of the compositions we explored could be stabilized epitaxially; the targeted compounds decomposed immediately into a mixture of other phases. So, this path to high-temperature superconductivity in nickelates at ambient pressure does not seem promising. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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19 pages, 46658 KiB

Open AccessArticle

Comparison of the Field Trapping Ability of MgB₂ and Hybrid Disc-Shaped Layouts

by Michela Fracasso, Roberto Gerbaldo, Gianluca Ghigo, Daniele Torsello, Yiteng Xing, Pierre Bernstein, Jacques Noudem and Laura Gozzelino

Materials 2024, 17(5), 1201; https://doi.org/10.3390/ma17051201 - 5 Mar 2024

Viewed by 867

Abstract

Superconductors have revolutionized magnet technology, surpassing the limitations of traditional coils and permanent magnets. This work experimentally investigates the field-trapping ability of a MgB₂ disc at various temperatures and proposes new hybrid (MgB₂-soft iron) configurations using a numerical approach based [...] Read more.

Superconductors have revolutionized magnet technology, surpassing the limitations of traditional coils and permanent magnets. This work experimentally investigates the field-trapping ability of a MgB₂ disc at various temperatures and proposes new hybrid (MgB₂-soft iron) configurations using a numerical approach based on the vector potential (

\vec{A}

) formulation. The experimental characterization consists in measurements of trapped magnetic flux density carried out using cryogenic Hall probes located at different radial positions over the MgB₂ sample, after a field cooling (FC) process and the subsequent removal of the applied field. Measurements were performed also as a function of the distance from the disc surface. The numerical modelling of the superconductor required the evaluation of the critical current density dependence on the magnetic flux density (J_c(B)) obtained through an iterative procedure whose output were successfully validated by the comparison between experimental and computed data. The numerical model, upgraded to also describe the in-field behavior of ARMCO soft iron, was then employed to predict the field-trapping ability of hybrid layouts of different shapes. The most promising results were achieved by assuming a hollow superconducting disc filled with a ferromagnetic (FM) cylinder. With such a geometry, optimizing the radius of the FM cylinder while the external dimensions of the superconducting disc are kept unchanged, an improvement of more than 30% is predicted with respect to the full superconducting disc, assuming a working temperature of 20 K. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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10 pages, 1800 KiB

Open AccessArticle

CMOS-Compatible Ultrathin Superconducting NbN Thin Films Deposited by Reactive Ion Sputtering on 300 mm Si Wafer

by Zihao Yang, Xiucheng Wei, Pinku Roy, Di Zhang, Ping Lu, Samyak Dhole, Haiyan Wang, Nicholas Cucciniello, Nag Patibandla, Zhebo Chen, Hao Zeng, Quanxi Jia and Mingwei Zhu

Materials 2023, 16(23), 7468; https://doi.org/10.3390/ma16237468 - 30 Nov 2023

Viewed by 1289

Abstract

We report a milestone in achieving large-scale, ultrathin (~5 nm) superconducting NbN thin films on 300 mm Si wafers using a high-volume manufacturing (HVM) industrial physical vapor deposition (PVD) system. The NbN thin films possess remarkable structural uniformity and consistently high superconducting quality [...] Read more.

We report a milestone in achieving large-scale, ultrathin (~5 nm) superconducting NbN thin films on 300 mm Si wafers using a high-volume manufacturing (HVM) industrial physical vapor deposition (PVD) system. The NbN thin films possess remarkable structural uniformity and consistently high superconducting quality across the entire 300 mm Si wafer, by incorporating an AlN buffer layer. High-resolution X-ray diffraction and transmission electron microscopy analyses unveiled enhanced crystallinity of (111)-oriented δ-phase NbN with the AlN buffer layer. Notably, NbN films deposited on AlN-buffered Si substrates exhibited a significantly elevated superconducting critical temperature (~2 K higher for the 10 nm NbN) and a higher upper critical magnetic field or H_c2 (34.06 T boost in H_c2 for the 50 nm NbN) in comparison with those without AlN. These findings present a promising pathway for the integration of quantum-grade superconducting NbN films with the existing 300 mm CMOS Si platform for quantum information applications. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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9 pages, 739 KiB

Open AccessEditor’s ChoiceArticle

Ion-Selective Scattering Studied Using the Variable-Energy Electron Irradiation in the Ba_0.2K_0.8Fe₂As₂ Superconductor

by Kyuil Cho, Marcin Kończykowski, Makariy A. Tanatar, Igor I. Mazin, Yong Liu, Thomas A. Lograsso and Ruslan Prozorov

Materials 2023, 16(13), 4520; https://doi.org/10.3390/ma16134520 - 22 Jun 2023

Cited by 2 | Viewed by 1031

Abstract

Low-temperature variable-energy electron irradiation was used to induce non-magnetic disorder in a single crystal of a hole-doped iron-based superconductor, Ba

_{1 - x}

K

_{x}

Fe

_{2}

As

_{2}

, x = 0.80. To avoid systematic errors, the beam energy was adjusted non-consequently [...] Read more.

Low-temperature variable-energy electron irradiation was used to induce non-magnetic disorder in a single crystal of a hole-doped iron-based superconductor, Ba

_{1 - x}

K

_{x}

Fe

_{2}

As

_{2}

, x = 0.80. To avoid systematic errors, the beam energy was adjusted non-consequently for five values between 1.0 and 2.5 MeV when sample resistance was measured in situ at 22 K. For all energies, the resistivity raises linearly with the irradiation fluence suggesting the creation of uncorrelated dilute point-like disorder (confirmed by simulations). The rate of the resistivity increase peaks at energies below 1.5 MeV. Comparison with calculated partial cross-sections points to the predominant creation of defects in the iron sublattice. Simultaneously, superconducting

T_{c}

, measured separately between the irradiation runs, is monotonically suppressed as expected, since it depends on the total scattering rate, hence on the total cross-section, which is a monotonically increasing function of the energy. Our work experimentally confirms an often-made assumption of the dominant role of the iron sub-lattice in iron-based superconductors. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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13 pages, 3264 KiB

Open AccessArticle

Design and Characteristic Analysis of an Axial Flux High-Temperature Superconducting Motor for Aircraft Propulsion

by Jun-Yeop Lee, Gi-Dong Nam, In-Keun Yu and Minwon Park

Materials 2023, 16(9), 3587; https://doi.org/10.3390/ma16093587 - 7 May 2023

Cited by 4 | Viewed by 2358

Abstract

In line with global environmental regulations, the demand for eco-friendly and highly efficient aircraft propulsion systems is increasing. The combination of axial flux motors and superconductors could be a key technology used to address these needs. In this paper, an axial flux high [...] Read more.

In line with global environmental regulations, the demand for eco-friendly and highly efficient aircraft propulsion systems is increasing. The combination of axial flux motors and superconductors could be a key technology used to address these needs. In this paper, an axial flux high temperature superconducting (HTS) motor for aircraft propulsion was designed and its characteristics were analyzed. A 2G HTS wire with high magnetic flux characteristic was used for the field winding of the 120 kW axial flux HTS motor, and the rotational speed and rated voltage of the motor were 2000 rpm and 220 V, respectively. The axial flux HTS motor implements a revolving armature type for solid cooling of the HTS field coil. The electromagnetic and thermal features of the motor were analyzed and designed utilizing a 3D finite element method program. The HTS coil was maintained at the target temperature by effectively designing the current lead and cooling system to minimize heat loss. These results can be effectively used in the design of propulsion systems for large commercial aircraft in the future as well as for the design of small aircraft with less than 4 seats. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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18 pages, 3892 KiB

Open AccessArticle

Cometal Addition Effect on Superconducting Properties and Granular Behaviours of Polycrystalline FeSe_0.5Te_0.5

by Manasa Manasa, Mohammad Azam, Tatiana Zajarniuk, Ryszard Diduszko, Tomasz Cetner, Andrzej Morawski, Andrzej Wiśniewski and Shiv J. Singh

Materials 2023, 16(7), 2892; https://doi.org/10.3390/ma16072892 - 5 Apr 2023

Cited by 4 | Viewed by 1744

Abstract

The enhanced performance of superconducting FeSe_0.5Te_0.5 materials with added micro-sized Pb and Sn particles is presented. A series of Pb- and Sn-added FeSe_0.5Te_0.5 (FeSe_0.5Te_0.5 + xPb + ySn; x = y = [...] Read more.

The enhanced performance of superconducting FeSe_0.5Te_0.5 materials with added micro-sized Pb and Sn particles is presented. A series of Pb- and Sn-added FeSe_0.5Te_0.5 (FeSe_0.5Te_0.5 + xPb + ySn; x = y = 0–0.1) bulks are fabricated by the solid-state reaction method and characterized through various measurements. A very small amount of Sn and Pb additions (x = y ≤ 0.02) enhance the transition temperature (T_c^onset) of pure FeSe_0.5Te_0.5 by ~1 K, sharpening the superconducting transition and improving the metallic nature in the normal state, whereas larger metal additions (x = y ≥ 0.03) reduce T_c^onset by broadening the superconducting transition. Microstructural analysis and transport studies suggest that at x = y > 0.02, Pb and Sn additions enhance the impurity phases, reduce the coupling between grains, and suppress the superconducting percolation, leading to a broad transition. FeSe_0.5Te_0.5 samples with 2 wt% of cometal additions show the best performance with their critical current density, J_c, and the pinning force, F_p, which might be attributable to providing effective flux pinning centres. Our study shows that the inclusion of a relatively small amount of Pb and Sn (x = y ≤ 0.02) works effectively for the enhancement of superconducting properties with an improvement of intergrain connections as well as better phase uniformity. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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13 pages, 3367 KiB

Open AccessArticle

Measurements of Surface Impedance in MgB₂ in DC Magnetic Fields: Insights in Flux-Flow Resistivity

by Andrea Alimenti, Kostiantyn Torokhtii, Pablo Vidal García, Enrico Silva, Mihai Alexandru Grigoroscuta, Petre Badica, Adrian Crisan and Nicola Pompeo

Materials 2023, 16(1), 205; https://doi.org/10.3390/ma16010205 - 26 Dec 2022

Cited by 1 | Viewed by 1584

Abstract

We present the multifrequency measurements of the surface resistance of spark-plasma-sintered MgB

_{2}

performed through a dielectric loaded resonator operating at 16.5 and 26.7 GHz. By normally applying magnetic fields ≤1.2 T to the sample surface, we drove it in the mixed state. [...] Read more.

We present the multifrequency measurements of the surface resistance of spark-plasma-sintered MgB

_{2}

performed through a dielectric loaded resonator operating at 16.5 and 26.7 GHz. By normally applying magnetic fields ≤1.2 T to the sample surface, we drove it in the mixed state. By means of data-rooted analysis, we found that the sample vortex dynamics could be fully described within a single-component approach. Pinning phenomena were present and characterized by a depinning frequency smaller than the measurement ones. The multiband nature of the superconductor emerged in the flux-flow resistivity, whose field dependence could be interpreted well within theoretical models. By exploiting them, the upper critical field was extracted in the low-temperature range, which exhibited a consistent temperature trend with the values obtained at the onset of the resistive transition near

T_{c}

, and was well in line with literature data on other polycrystalline samples. Full article

(This article belongs to the Special Issue Novel Superconducting Materials and Applications of Superconductivity)

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