Room-temperature superconductivity is known for its seemingly contradictory properties, which initially led researchers to attribute these inconsistencies to the presence of impurities in the synthesis process of apatite-like materials, specifically LK99. However, even when Doctor Dai used highly pure samples for his research, the same contradictory results were observed, prompting a deeper investigation into the underlying mystery.
The crystal structure of the apatite phase is well-understood, especially since the introduction of LK99. Its more detailed electronic structure has been thoroughly analyzed using quantum mechanical calculations by theoretical scholars. Although the information on the electronic structural characteristics is clear, it only offers a microscopic understanding of apatite, which isn’t directly applicable to real-world applications. The performance of a material is crucial for its application, and without a clear understanding of its properties, application remains elusive.
Researchers attempting to work with the LK99 process mainly focus on the superconducting and magnetic properties. Due to the presence of impurities in the samples, such as Cu2S and metallic phases, it’s challenging to clarify the complex relationship between these properties and the structure, presenting a significant technical challenge.
Many suggest that achieving a pure phase could be a solution. If the properties of the pure apatite phase could be measured, it would potentially reveal conclusive results. However, the apatite phase itself is complex, with a crystal structure that is standard in three dimensions but also features unique one-dimensional characteristics, similar to amber with an enclosed bubble of liquid. It appears as a solid stone but contains liquid signals, leading to a plethora of contradictory experimental results. For instance, magnetic measurements might indicate superconductivity, while electrical properties suggest it’s an insulator, presenting many contradictory signals.
The issue with the apatite phase is fundamentally about understanding the basic principles of superconductors. Traditional metallic superconductors are like ice formed from liquid. Cuprates and iron-based superconductors are like clay that only becomes superconducting when mixed with water. The new room-temperature superconducting systems, resembling a glass phase, would not typically be superconducting. However, in the lead apatite system, the presence of a one-dimensional channel that, if filled, could act as a conductive tube allowing for superconductivity.
This structure is unusual and has not been encountered in traditional superconductivity research, where it’s well known that insulators cannot carry charge carriers and thus cannot be superconducting. The two-dimensional layered structures of cuprates and iron-based superconductors are essentially Mott insulators and can be doped to become semiconductors. Other typical insulators cannot achieve charge carriers through doping. Therefore, superconductivity researchers have not focused on insulating salt systems. Additionally, one-dimensional channel structures have been largely overlooked due to the lack of reference models and established techniques for doping, making it an underexplored area in superconductivity research.
In summary, to advance room-temperature superconductivity research, it’s essential to understand the basic principles of traditional superconductors and to clearly identify the unique characteristics of the new system. By grasping the one-dimensional channel feature of the apatite phase and understanding its structural characteristics, it becomes easier to comprehend its fundamental properties and potential applications.