Superconductivity and Magnetism in Two-Dimensional and Layered Materials

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "2D and Carbon Nanomaterials".

Deadline for manuscript submissions: 30 April 2025 | Viewed by 5204

Special Issue Editor


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Guest Editor
Department of Applied Science and Technology, Politecnico di Torino, Turin, Italy
Interests: superconductivity; 2D materials; electric transport measurements; scanning probe microscopy; thin films and nanotechnology

Special Issue Information

Dear Colleagues,

Two-dimensional and layered materials are an emerging class of compounds that have attracted unprecedented attention from the scientific community in the last twenty years. Most of the research efforts have so far been devoted to the exploration of their unique electronic, optical, and optoelectronic properties, also in light of potential technological applications.

However, more exotic quantum phases have also been discovered in this class of materials, including superconductivity and various types of magnetic order. Given that several of these fascinating phenomena still elude a comprehensive understanding and that new two-dimensional and layered superconducting and/or magnetic compounds are continuously being discovered, the field is in need of novel experimental and theoretical investigations on a fundamental level. Additionally, a subset of these materials is close to attaining technological maturity, which will in turn pave the way for their usage in industry-grade applications with a foreseen impact in different fields ranging from energy storage, quantum computing and sensing, spintronics, and more.

This Special Issue therefore aims at providing a space for experimental, computational, and theoretical studies concerning the superconducting and/or magnetic properties of two-dimensional and layered materials, as well as their exploitation in devices and technological applications. Full articles, short communications, and review papers are welcome for submission.

Dr. Erik Piatti
Guest Editor

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Keywords

  • two-dimensional materials
  • layered materials
  • superconductivity
  • magnetism
  • synthesis and fabrication
  • characterization techniques
  • theoretical modelling

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Published Papers (5 papers)

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Research

9 pages, 9872 KiB  
Article
Doping the Spin-Polarized Graphene Minicone on Ni(111)
by Cesare Tresca, Gianni Profeta and Federico Bisti
Nanomaterials 2024, 14(17), 1448; https://doi.org/10.3390/nano14171448 - 4 Sep 2024
Viewed by 539
Abstract
In the attempt to induce spin-polarized states in graphene (Gr), rare-earth deposition on Gr/Co(0001) has been demonstrated to be a successful strategy: the coupling of graphene with the cobalt substrate provides spin-polarized conical-shaped states (minicone) and the rare-earth deposition brings these states at [...] Read more.
In the attempt to induce spin-polarized states in graphene (Gr), rare-earth deposition on Gr/Co(0001) has been demonstrated to be a successful strategy: the coupling of graphene with the cobalt substrate provides spin-polarized conical-shaped states (minicone) and the rare-earth deposition brings these states at the Fermi level. In this manuscript, we theoretically explore the feasibility of an analogue approach applied on Gr/Ni(111) doped with rare-earth ions by means of density functional theory calculations. Even if not well mentioned in the literature, this system owns a minicone, similar to the cobalt case. By testing different rare-earth ions, not only do we suggest which one can provide the required doping but we also explain the effect behind this proper charge transfer. Full article
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15 pages, 895 KiB  
Article
Superconductivity of Co-Doped CaKFe4As4 Investigated via Point-Contact Spectroscopy and London Penetration Depth Measurements
by Erik Piatti, Daniele Torsello, Francesca Breccia, Tsuyoshi Tamegai, Gianluca Ghigo and Dario Daghero
Nanomaterials 2024, 14(15), 1319; https://doi.org/10.3390/nano14151319 - 5 Aug 2024
Viewed by 993
Abstract
The iron-based superconductors (IBSs) of the recently discovered 1144 class, unlike many other IBSs, display superconductivity in their stoichiometric form and are intrinsically hole doped. The effects of chemical substitutions with electron donors are thus particularly interesting to investigate. Here, we study the [...] Read more.
The iron-based superconductors (IBSs) of the recently discovered 1144 class, unlike many other IBSs, display superconductivity in their stoichiometric form and are intrinsically hole doped. The effects of chemical substitutions with electron donors are thus particularly interesting to investigate. Here, we study the effect of Co substitution in the Fe site of CaKFe4As4 single crystals on the critical temperature, on the energy gaps, and on the superfluid density by using transport, point-contact Andreev-reflection spectroscopy (PCARS), and London penetration depth measurements. The pristine compound (Tc36 K) shows two isotropic gaps whose amplitudes (Δ1 = 1.4–3.9 meV and Δ2 = 5.2–8.5 meV) are perfectly compatible with those reported in the literature. Upon Co doping (up to ≈7% Co), Tc decreases down to ≃20 K, the spin-vortex-crystal order appears, and the low-temperature superfluid density is gradually suppressed. PCARS and London penetration depth measurements perfectly agree in demonstrating that the nodeless multigap structure is robust upon Co doping, while the gap amplitudes decrease as a function of Tc in a linear way with almost constant values of the gap ratios 2Δi/kBTc. Full article
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18 pages, 895 KiB  
Article
Optical Absorption in Tilted Geometries as an Indirect Measurement of Longitudinal Plasma Waves in Layered Cuprates
by Niccolò Sellati, Jacopo Fiore, Claudio Castellani and Lara Benfatto
Nanomaterials 2024, 14(12), 1021; https://doi.org/10.3390/nano14121021 - 13 Jun 2024
Viewed by 790
Abstract
Electromagnetic waves propagating in a layered superconductor with arbitrary momentum, with respect to the main crystallographic directions, exhibit an unavoidable mixing between longitudinal and transverse degrees of freedom. Here we show that this basic physical mechanism explains the emergence of a well-defined absorption [...] Read more.
Electromagnetic waves propagating in a layered superconductor with arbitrary momentum, with respect to the main crystallographic directions, exhibit an unavoidable mixing between longitudinal and transverse degrees of freedom. Here we show that this basic physical mechanism explains the emergence of a well-defined absorption peak in the in-plane optical conductivity when light propagates at small tilting angles relative to the stacking direction in layered cuprates. More specifically, we show that this peak, often interpreted as a spurious leakage of the c-axis Josephson plasmon, is instead a signature of the true longitudinal plasma mode occurring at larger momenta. By combining a classical approach based on Maxwell’s equations with a full quantum derivation of the plasma modes based on modeling the superconducting phase degrees of freedom, we provide an analytical expression for the absorption peak as a function of the tilting angle and light polarization. We suggest that an all-optical measurement in tilted geometry can be used as an alternative way to access plasma-wave dispersion, usually measured by means of large-momenta scattering techniques like resonant inelastic X-ray scattering (RIXS) or electron energy loss spectroscopy (EELS). Full article
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20 pages, 1087 KiB  
Article
Pump-Driven Opto-Magnetic Properties in Semiconducting Transition-Metal Dichalcogenides: An Analytical Model
by Habib Rostami, Federico Cilento and Emmanuele Cappelluti
Nanomaterials 2024, 14(8), 707; https://doi.org/10.3390/nano14080707 - 18 Apr 2024
Viewed by 906
Abstract
Single-layer transition-metal dichalcogenides provide an unique intrinsic entanglement between the spin/valley/orbital degrees of freedom and the polarization of scattered photons. This scenario gives rise to the well-assessed optical dichroism observed by using both steady and time-resolved probes. In this paper, we provide compact [...] Read more.
Single-layer transition-metal dichalcogenides provide an unique intrinsic entanglement between the spin/valley/orbital degrees of freedom and the polarization of scattered photons. This scenario gives rise to the well-assessed optical dichroism observed by using both steady and time-resolved probes. In this paper, we provide compact analytical modeling of the onset of a finite Faraday/Kerr optical rotation upon shining with circularly polarized light. We identify different optical features displaying optical rotation at different characteristic energies, and we describe in an analytical framework the time-dependence of their intensities as a consequence of the main spin-conserving and spin-flip processes. Full article
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16 pages, 3393 KiB  
Article
Green-Light GaN p-n Junction Luminescent Particles Enhance the Superconducting Properties of B(P)SCCO Smart Meta-Superconductors (SMSCs)
by Qingyu Hai, Honggang Chen, Chao Sun, Duo Chen, Yao Qi, Miao Shi and Xiaopeng Zhao
Nanomaterials 2023, 13(23), 3029; https://doi.org/10.3390/nano13233029 - 27 Nov 2023
Cited by 2 | Viewed by 1238
Abstract
Superconducting materials exhibit unique physical properties and have great scientific value and vast industrial application prospects. However, due to limitations, such as the critical temperature (TC) and critical current density (JC), the large-scale application of superconducting materials [...] Read more.
Superconducting materials exhibit unique physical properties and have great scientific value and vast industrial application prospects. However, due to limitations, such as the critical temperature (TC) and critical current density (JC), the large-scale application of superconducting materials remains challenging. Chemical doping has been a commonly used method to enhance the superconductivity of B(P)SCCO. However, satisfactory enhancement results have been difficult to achieve. In this study, we introduce green-light GaN p-n junction particles as inhomogeneous phases into B(P)SCCO polycrystalline particles to form a smart meta-superconductor (SMSC) structure. Based on the electroluminescence properties of the p-n junction, the Cooper pairs were stimulated and strengthened to enhance the superconductivity of B(P)SCCO. The experimental results demonstrate that the introduction of inhomogeneous phases can indeed enhance the critical temperature TC, critical current density JC, and complete diamagnetism (Meissner effect) of B(P)SCCO superconductors. Moreover, when the particle size of the raw material of B(P)SCCO is reduced from 30 to 5 μm, the grain size of the sintered samples also decreases, and the optimal doping concentration of the inhomogeneous phases increases from 0.15 wt.% to 0.2 wt.%, further improving the superconductivity. Full article
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