Indications of superconductivities in blend of variant apatite and covellite

Abstract: Through heavily doping sulfur into an apatite framework, we synthesize a new blend mainly comprising variant apatite and covellite (copper sulfide). Magnetic measurement exhibits that significant diamagnetism appears at around 260 K and drops dramatically below 30 K implying coexistence of two superconducting phases. The upper critical magnetic field is larger than 1000 Oe at 250 K. Electric measurement manifests that the current-voltage curves deviate from the normal linear lineshape suggesting the presence of zero-resistance effect, and the critical current is around 50 $\mu$A at 140 K. These exotic magnetic and electric features strongly indicate these two components, variant apatite and covellite, individually trigger two superconducting phases at near-room and low temperatures.

• The paper presents evidence for superconductivity in a blend of variant apatite and covellite synthesized via hydrothermal method, observing two phases around 260 K and below 30 K.
• Magnetic measurements indicate significant diamagnetism at 260 K and an upper critical field exceeding 1000 Oe at 250 K, while electric tests show non-linear response and a critical current near 50 μA at 140 K.
• Material analysis via XRD and EPMA confirms sulfur substitution leading to variant apatite and covellite, suggesting a proximity effect mechanism and highlighting the potential for near-room temperature superconductivity through synthesis control.

Indications of Superconductivities in a Blend of Variant Apatite and Covellite

The paper presents a novel investigation into superconductivity phenomena within a synthesized blend of variant apatite and covellite, achieved through the incorporation of sulfur into a copper apatite framework. The research reveals the existence of two distinct superconducting phases, elucidated through careful magnetic and electric measurements.

Key Findings and Methodology

The approach centers on heavily doping sulfur into the apatite framework, yielding a compound primarily comprising variant apatite and covellite (copper sulfide). The synthesis process, performed via a hydrothermal method at elevated pressure, ensures the retention of essential structural integrity, which facilitates the coexistence of two superconducting phases. The efficacy of this method is exemplified by the resultant superconductivity observed around 260 K and below 30 K, far exceeding conventional expectations for copper-sulfur compounds.

Magnetic measurements indicated significant diamagnetism at approximately 260 K, suggesting the onset of the first superconducting phase, whereas the second phase is apparent at lower temperatures. Notably, the upper critical field ($H_{\rm c2}$) at 250 K surpassed 1000 Oe, evidencing robust superconducting characteristics. The presence of a zero-resistance state was supported by electric measurements demonstrating deviations from a standard linear current-voltage response, with a critical current near 50 μA at 140 K.

Material Characterization and Analysis

X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were pivotal in confirming the phase composition and distribution within the compound. Observations revealed a substantial substitution of phosphor and oxygen by sulfur, culminating in a unique variant apatite structure. The transformation to covellite, detailed via EPMA mapping, indicated sulfur concentrations exceeding those of copper, which could suggest the formation of copper persulfide.

The MT curves derived from magnetization assessments displayed conventional superconducting behavior, though lacking distinct Meissner phase characteristics due to phase intermixing. The authors attribute this to the association between variant apatite and covellite, and propose a proximity effect as a mechanism linking these phenomena.

Implications and Future Research Directions

The investigation introduces a promising avenue for studying superconductivity at near-room temperatures, facilitated by the interplay between variant apatite and covellite. The potential for practical applications hinges on mastering synthesis parameters to optimize superconducting properties. Future research avenues could explore fine-tuning the doping process, potentially leading to enhanced stability and performance of the materials. Further experimental work could also focus on alternative synthesis routes or modifications to the apatite framework to support industrial scalability and application in superconducting technologies.

In conclusion, the research lays crucial groundwork for advancing the understanding of high-temperature superconductivity in novel material blends, underscoring both the theoretical and practical significance of such discoveries. As the capabilities to synthesize and control these complex structures progress, the impact on the field of materials science and its applications could be considerable.