Absence of superconductivity in LK-99 at ambient conditions (2308.03544v3)

Abstract: The report of synthesis of modified Lead apatite (LK-99) with evidence of superconductivity at more than boiling water temperature has steered the whole scientific community. There have been several failures to reproduce superconductivity in LK-99 including partial successes. Here, we have continued our efforts to synthesize phase pure LK-99 with improved precursors. The process has been followed as suggested by Sukbae Lee et. al., [1,2]. The phase purity of each precursor is evidenced by Powder X-ray diffraction (PXRD) and well fitted by Rietveld refinement. The PXRD confirms the synthesis of phase pure polycrystalline LK-99 with apatite structure. The freshly synthesized sample does not show any signature of superconductivity levitation on a magnet (diamagnetism). The magnetization measurements on SQUID also show that LK-99 is diamagnetic at 280 K, there is no sign of superconductivity in LK-99 at room temperature. Moreover, we have also performed first principle calculations to investigate the electronic band structure of the LK-99 near Fermi level. Our study verifies that the Cu doped lead apatite (LK-99) has bands crossing at Fermi level, indicating generation of strong correlation in the system.

• The paper establishes that LK-99, synthesized using copper-doped lead apatite, shows no superconductivity at ambient conditions.
• It confirms phase purity with PXRD and finds high electrical resistance and absence of magnetic levitation using SQUID magnetometry.
• DFT calculations further support the null result by revealing no electronic features associated with superconducting behavior.

An Analysis of the Absence of Superconductivity in LK-99 under Ambient Conditions

The manuscript authored by Kumar et al. provides a compelling investigation into the purported superconducting characteristics of the synthesized compound LK-99 at ambient conditions. The exploration of room-temperature superconductivity heralds substantial implications for technological advancement; however, the reproducibility of such phenomena remains critically debated. In this paper, the researchers meticulously replicated the synthesis procedures delineated by the original proposers of LK-99, using copper-doped lead apatite structures, yet, their results indicate an absence of superconductivity at room temperature.

Synthesis and Characterization

The synthesis of LK-99 involved precise phase-pure preparation of its precursors using copper phosphide and lead sulfate. Each precursor's phase purity was verified via powder X-ray diffraction (PXRD) and Rietveld refinement, ensuring an accurate follow-through on the synthesis route originally suggested by Sukbae Lee et al. The PXRD analysis confirmed the construction of a phase-pure LK-99, crystallizing in a lead apatite structure. The researchers emphasized the significance of precursor phase purity as a critical factor for superconductivity, a point consistent with literature findings that highlight synthesis conditions' roles in achieving desirable superconductive properties.

Examination for Superconductivity

However, the expected superconductive behaviors—such as magnetic levitation and signatures of the Meissner effect—were conspicuously absent. Measurements conducted at 280K using SQUID magnetometry depicted diamagnetism but no sign of superconductivity. Furthermore, the synthesized sample demonstrated high electrical resistance, contradicting expectations for a superconductive material. These experimental results present a notable divergence from previous claims that suggested superconductivity above 400K.

Computational Insights

To complement the experimental work, the paper also utilized first-principles calculations via Density Functional Theory (DFT) to probe the electronic band structure near the Fermi level. These simulations indicated no direct evidence of superconductivity, despite exhibiting bands crossing near the Fermi level, which typically signifies strong electronic correlation purportedly supportive of superconductive states. This analytical juxtaposition presents a significant counterpoint to theories based on strong electron correlation-induced superconductivity in copper-doped lead apatite.

Implications and Future Directions

The findings set forth by Kumar et al. hold considerable implications. They question the reproducibility and validity of earlier reports claiming room-temperature superconductivity in LK-99, stressing the need for rigorous validation and operational consistency in alleged superconducting materials. The observed discrepancies accentuate the necessity for additional scrutiny of synthesis approaches, precursor purity, and experimental conditions that may influence phase formation and electronic properties.

Given the ongoing advances in understanding high-temperature superconductors, these results could provoke further explorations into alternative compound adjustments or entirely new materials that might fulfill the promise of practical superconductivity above ambient conditions. Enhanced computational models simulating more diverse dopant configurations and their effects could also elucidate pathways toward genuine superconductive behavior in similar material systems.

In summary, while the paper does not validate the presence of superconductivity within LK-99 at room temperature, it provides an essential contribution to ongoing research, emphasizing the importance of empirical verification and theoretical analysis in the development of advanced superconducting materials.