On July 23, 2023, a South Korean research team claimed that they had successfully developed a superconductor at room temperature and normal pressure , called
LK-99. This discovery has aroused widespread concern and discussion in the scientific community.
However, the study's results also raised doubts among some scientists. Some have expressed doubts about the authenticity of the data, arguing that the results of this study need more validation and replication.
On August 1, 2023, the Institute of Physics of the Chinese Academy of Sciences has initially reproduced the superconducting properties of LK-99. This result still needs further research and verification.
Korean team Arxiv paper: https://arxiv.org/ftp/arxiv/papers/2307/2307.12008.pdf
Article directory
1. What is a room temperature superconductor
The discovery and development of room-temperature superconductors have had a profound impact on the fields of science and technology.
A superconductor is a substance with zero electrical resistance , meaning that electricity can flow through it without loss . However, conventional superconductors can only work at extremely low temperatures , which limits their practical applications. If superconductivity can be realized at room temperature, the application fields of superconductivity technology will be greatly expanded.
Here are some possible impacts and applications of room-temperature superconductors:
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Energy transmission : Superconductors can transmit electricity without loss, which means we can transmit electricity with almost no energy loss in the process. This will greatly improve the efficiency of power delivery and reduce energy consumption.
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Magnetic levitation technology : Superconductors can generate a strong diamagnetic field in a magnetic field. This feature can be used in vehicles such as maglev trains to achieve frictionless, high-speed transportation.
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Medical equipment and scientific instruments : Superconductors are widely used in fields such as medical imaging (such as MRI) and particle accelerators. Room-temperature superconductors could lower the operating and maintenance costs of these devices, making these high-end devices accessible to more institutions.
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Quantum Computing : Superconductors are one of the key technologies to realize quantum computing. Room-temperature superconductors could lead to advances in quantum computing, making quantum computers more practical and affordable to build and run.
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Environmental protection : The use of superconducting power lines and equipment will greatly reduce energy loss, help reduce carbon emissions, and have a positive impact on environmental protection.
The successful development of room-temperature superconductors will have a profound impact on many fields such as science and technology, energy, transportation, and medical treatment, and will promote the technological progress of human society.
This will be a revolutionary technological advancement.
2. Article reading
2.1 Summary
The article reports for the first time the experimental results of the successful synthesis of superconductors at room temperature and normal pressure. This new type of superconductor was named LK-99, and its superconducting properties were verified by critical temperature (Tc), zero resistance, critical current (Ic), critical magnetic field (Hc) and the Meissner effect .
The superconducting properties of LK-99 arise from tiny structural distortions rather than external factors such as temperature and pressure.
This distortion is due to the volume shrinkage (0.48%) caused by copper ions (Cu2+) replacing lead ions (Pb2+) in the phosphate insulating network. This shrinkage generates stress, which is simultaneously transferred to the Pb(1) of the cylinder, causing distortion at the cylinder-column interface, thereby creating a superconducting quantum well at the interface.
The unique structure of LK-99 allows tiny distortion structures to be maintained on the interface, which is the most important factor for LK-99 to maintain and exhibit superconductivity at room temperature and pressure.
In addition, the article discusses the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR), heat capacity, and superconducting quantum interference device (SQUID) data of LK-99 to explain the -99 superconducting properties.
2.2 Main content
Since the discovery of the first superconductors, there have been many worldwide efforts to find new room-temperature superconductors, either based on experimental clarity or from a theoretical perspective. Recently, the successful development of room-temperature superconductors based on hydrogen sulfide and yttrium superhydride has attracted global attention due to the high-frequency hydrogen phonon modes predicted by the theory of strong electron-phonon coupling. However, due to the extremely high pressure, these superconductors are difficult to implement in practical devices, so more efforts are being made to overcome the high pressure problem.
In order to solve the problem of temperature and pressure, we successfully synthesized a room-temperature superconductor working under normal pressure for the first time, and we named this superconductor LK-99. The superconductivity of LK-99 is demonstrated by the critical temperature (Tc), zero resistance, critical current (Ic), critical magnetic field (Hc) and the Meissner effect. We collected and analyzed several kinds of data in detail, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR), heat capacity, and superconducting quantum interference device (SQUID) data, to Solving the mystery of LK-99's superconductivity. In this paper, we report and discuss our new findings, including superconducting quantum wells, which are related to the superconductivity of LK-99.
From Figure 1, the authors draw the following conclusions:
Figure 1(a) shows the measured voltage versus applied current at different temperatures (298 K ~ 398 K). The measurement was performed in a vacuum of 10-3 Torr, changing the direct current (DC) polarity for every 20 K increase in temperature.
Figure 1(b) shows a thin film with zero resistance. Specific resistance was measured in the range of 10-6 to 10-9 Ω·cm in various volume samples. Furthermore, thin films of LK-99 showed zero resistance in the temperature range below 400 K.
Figure 1(c) shows the measured voltage versus applied current at different external magnetic fields (Oe).
Figure 1(d) demonstrates the field-cooled and zero-field-cooled DC magnetization at 10 Oe magnetic field. These results show that even at a magnetic field of 10 Oe, the superconducting phase persists up to a temperature of 400 K.
Figure 1(e) shows the relationship between critical current and critical temperature. Even at 400 K and a magnetic field of 3000 Oe or higher, the critical current value is still non-zero (7 mA). Therefore, the authors judged that the critical temperature of LK-99 exceeds 400 K.
Figure 1(f) shows the relationship between critical current and critical magnetic field.
These results indicate that LK-99 still exhibits superconductivity at a temperature of 400 K and a magnetic field of 3000 Oe or higher. Furthermore, since LK-99 has a polycrystalline morphology, the non-uniform resistance of the bulk sample can be explained by the grain boundaries of the polycrystalline superconducting phase, intergranular eddy currents, and free eddy currents.
Therefore, we judge that the critical temperature of LK-99 exceeds 400 K. In addition, since LK-99 has a polycrystalline morphology as shown in Figure 2, the inhomogeneity of the resistivity of the bulk sample can be explained by the grain boundary and intergranular resistivity. Polycrystalline eddy current, free eddy current superconducting phase. Josephson-like phenomena (Fig. S1(a) in Supplementary Material) for underdamped grain-coupled superconductors (23) and intergranular or intragranular thermoelectric effects (24 -26) Networks were also observed (Fig. S1(b) in the supplementary material).
Figure 2: Shows X-ray diffraction (XRD) results of LK-99 matched to COD. Raw XRD data were only subjected to Kα2 stripping without any other processing.