Experimental demonstration of superconducting critical temperature increase in electromagnetic metamaterials

The Influence of Electroluminescent Inhomogeneous Phase Addition on Enhancing MgB2 Superconducting Performance and Magnetic Flux Pinning

As a highly regarded superconducting material with a concise layered structure, MgB2 has attracted significant scientific attention and holds vast potential for applications. However, its limited current-carrying capacity under high magnetic fields has greatly hindered its practical use. To address this issue, we have enhanced the superconducting performance of MgB2 by incorporating inhomogeneous phase nanostructures of p-n junctions with electroluminescent properties. Through temperature-dependent measurements of magnetization, electronic specific heat, and Hall coefficient under various magnetic fields, we have confirmed the crucial role of inhomogeneous phase electroluminescent nanostructures in improving the properties of MgB2. Experimental results demonstrate that the introduction of electroluminescent inhomogeneous phases effectively enhances the superconducting performance of MgB2. Moreover, by controlling the size of the electroluminescent inhomogeneous phases and optimizing grain connectivity, density, and microstructural uniformity, we can further improve the critical temperature (TC) and flux-pinning capability of MgB2 superconducting materials. Comprehensive studies on the physical properties of MgB2 superconducting structures added with p-n junction electroluminescent inhomogeneous phases also confirm the general effectiveness of electroluminescent inhomogeneous phases in enhancing the performance of superconducting materials.

An Improved Smart Meta-Superconductor MgB2

Increasing and improving the critical transition temperature (TC), current density (JC) and the Meissner effect (HC) of conventional superconductors are the most important problems in superconductivity research, but progress has been slow for many years. In this study, by introducing the p-n junction nanostructured electroluminescent inhomogeneous phase with a red wavelength to realize energy injection, we found the improved property of smart meta-superconductors MgB2, the critical transition temperature TC increases by 0.8 K, the current density JC increases by 37%, and the diamagnetism of the Meissner effect HC also significantly improved, compared with pure MgB2. Compared with the previous yttrium oxide inhomogeneous phase, the p-n junction has a higher luminescence intensity, a longer stable life and simpler external field requirements. The coupling between superconducting electrons and surface plasmon polaritons may be explained by this phenomenon. The realization of smart meta-superconductor by the electroluminescent inhomogeneous phase provides a new way to improve the performance of superconductors.

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content

A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the critical transition temperature (T_C) of B(P)SCCO by electroluminescence (EL) energy injection of inhomogeneous phases. However, the increase amplitude ΔT_C (ΔTC=TC−TC,pure) of T_C is relatively small. In this study, a smart meta-superconductor B(P)SCCO with different matrix sizes was designed. Three kinds of raw materials with different particle sizes were used, and different series of Y₂O₃:Sm³⁺, Y₂O₃, Y₂O₃:Eu³⁺, and Y₂O₃:Eu³⁺+Ag-doped samples and pure B(P)SCCO were prepared. Results indicated that the T_C of the Y₂O₃ or Y₂O₃:Sm³⁺ non-luminescent dopant doping sample is lower than that of pure B(P)SCCO. However, the T_C of the Y₂O₃:Eu³⁺+Ag or Y₂O₃:Eu³⁺ luminescent inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With the decrease of the raw material particle size from 30 to 5 μm, the particle size of the B(P)SCCO superconducting matrix in the prepared samples decreases, and the doping content of the Y₂O₃:Eu³⁺+Ag or Y₂O₃:Eu³⁺ increases from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content enhances the ΔT_C. When the particle size of raw material is 5 μm, the doping concentration of the luminescent inhomogeneous phase can be increased to 0.4%. At this time, the zero-resistance temperature and onset transition temperature of the Y₂O₃:Eu³⁺+Ag doped sample are 4 and 6.3 K higher than those of pure B(P)SCCO, respectively.

Hyperbolic Cooper-Pair Polaritons in Planar Graphene/Cuprate Plasmonic Cavities

Hyperbolic Cooper-pair polaritons (HCP) in cuprate superconductors are of fundamental interest due to their potential for providing insights into the nature of unconventional superconductivity. Here, we critically assess an experimental approach using near-field imaging to probe HCP in Bi₂Sr₂CaCu₂O_8+x (Bi-2212) in the presence of graphene surface plasmon polaritons (SPP). Our simulations show that inherently weak HCP features in the near-field can be strongly enhanced when coupled to graphene SPP in layered graphene/hexagonal boron nitride (hBN)/Bi-2212 heterostructures. This enhancement arises from our multilayered structures effectively acting as plasmonic cavities capable of altering collective modes of a layered superconductor by modifying its electromagnetic environment. The degree of enhancement can be selectively controlled by tuning the insulating spacer thickness with atomic precision. Finally, we verify the expected renormalization of room-temperature graphene SPP using near-field infrared imaging. Our modeling, augmented with data, attests to the validity of our approach for probing HCP modes in cuprate superconductors.

Order parameter focalization and critical temperature enhancement in synthetic networks of superconducting islands

A generalization of the de Gennes-Alexander micronetworks theory is presented. In this framework, the phase transition of synthetic networks of superconducting islands is described by means of a Ginzburg-Landau approach adapted to the case of granular systems. The general implications of the theory are carefully explained. As a specific example, we demonstrate that star networks support the exponential localization of the order parameter accompanied by an enhancement of the critical temperature of the system. These findings contribute to clarify the physics of the phase transitions in synthetic networks of Josephson-coupled superconducting islands.

Waveguide modes in Weyl semimetals with tilted dirac cones

We theoretically study unattenuated electromagnetic guided wave modes in centrosymmetric Weyl semimetal layered systems. By solving Maxwell's equations for the electromagnetic fields and using the appropriate boundary conditions, we derive dispersion relations for propagating modes in a finite-sized Weyl semimetal. Our findings reveal that for ultrathin structures and proper Weyl cones tilts, extremely localized guided waves can propagate along the semimetal interface over a certain range of frequencies. This follows from the anisotropic nature of the semimetal where the diagonal components of the permittivity can exhibit a tunable epsilon-near-zero response. From the dispersion diagrams, we determine experimentally accessible regimes that lead to high energy-density confinement in the Weyl semimetal layer. Furthermore, we show that the net system power can vanish all together, depending on the Weyl cone tilt and frequency of the electromagnetic wave. These effects are seen in the energy transport velocity, which demonstrates a substantial slowdown in the propagation of electromagnetic energy near critical points of the dispersion diagrams. Our results can provide guidelines in designing Weyl semimetal waveguides that can offer efficient control in the velocity and direction of energy flow.

Smart meta-superconductor MgB2 constructed by the dopant phase of luminescent nanocomposite

On the basis of the idea that the injecting energy will improve the conditions for the formation of Cooper pairs, a smart meta-superconductor (SMSC) was prepared by doping luminescent nanocomposite Y₂O₃:Eu³⁺/Ag in MgB₂. To improve the superconducting transition temperature (T_C) of the MgB₂-based superconductor, two types of Y₂O₃:Eu³⁺/Ag, which has the strong luminescence characteristic, with different sizes were prepared and marked as m-Y₂O₃:Eu³⁺/Ag and n-Y₂O₃:Eu³⁺/Ag. MgB₂ SMSC was prepared through an ex situ process. Results show that when the dopant content was fixed at 2.0 wt.%, the T_C of MgB₂ SMSC increased initially then decreased with the increase in the Ag content in the dopant. When the Ag content is 5%, the T_C of MgB₂ SMSC was 37.2–38.0 K, which was similar to that of pure MgB₂. Meanwhile, the T_C of MgB₂ SMSC doped with n-Y₂O₃:Eu³⁺/Ag increased initially then decreased basically with the increase in the content of n-Y₂O₃:Eu³⁺/Ag, in which the Ag content is fixed at 5%. The T_C of MgB₂ SMSC doped with 0.5 wt.% n-Y₂O₃:Eu³⁺/Ag was 37.6–38.4 K, which was 0.4 K higher than that of pure MgB₂. It is thought that the doping luminescent nanocomposite into the superconductor is a new means to improve the T_C of SMSC.

Observation of plasmon-phonons in a metamaterial superconductor using inelastic neutron scattering

A metamaterial approach is capable of drastically increasing the critical temperature,T c , of composite metal-dielectric superconductors as demonstrated by the tripling ofT c that was observed in bulk Al-Al2O3 coreshell metamaterials. A theoretical model based on the Maxwell-Garnett approximation provides a microscopic explanation of this effect in terms of electron-electron pairing mediated by a hybrid plasmon-phonon excitation. We report an observation of this excitation in Al-Al2O3 core-shell metamaterials using inelastic neutron scattering. This result provides support for this mechanism of superconductivity in metamaterials.

Enhanced superconductivity in aluminum-based hyperbolic metamaterials

One of the most important goals of condensed matter physics is materials by design, i.e. the ability to reliably predict and design materials with a set of desired properties. A striking example is the deterministic enhancement of the superconducting properties of materials. Recent experiments have demonstrated that the metamaterial approach is capable of achieving this goal, such as tripling the critical temperature T_C in Al-Al₂O₃ epsilon near zero (ENZ) core-shell metamaterial superconductors. Here, we demonstrate that an Al/Al₂O₃ hyperbolic metamaterial geometry is capable of a similar T_C enhancement, while having superior transport and magnetic properties compared to the core-shell metamaterial superconductors.

Using metamaterial nanoengineering to triple the superconducting critical temperature of bulk aluminum

Recent experiments have shown the viability of the metamaterial approach to dielectric response engineering for enhancing the transition temperature, T_c, of a superconductor. In this report, we demonstrate the use of Al₂O₃-coated aluminium nanoparticles to form the recently proposed epsilon near zero (ENZ) core-shell metamaterial superconductor with a T_c that is three times that of pure aluminium. IR reflectivity measurements confirm the predicted metamaterial modification of the dielectric function thus demonstrating the efficacy of the ENZ metamaterial approach to T_c engineering. The developed technology enables efficient nanofabrication of bulk aluminium-based metamaterial superconductors. These results open up numerous new possibilities of considerable Tc increase in other simple superconductors.