Kagome Metals Unlocked: A New Phase of Superconductivity

Kagome’s materials exhibit superconductivity with a unique distribution similar to the frequency of electron pairs, a discovery that overturns previous assumptions and could lead to the development of new superconducting materials.

This rigorous research, driven by theoretical data and reinforced by advanced experimental techniques, marks an important step towards achieving efficient quantum devices.

For about fifteen years, Kagome’s star-shaped tools reminiscent of Japanese basketry have attracted worldwide research. Only in 2018 scientists were able to create metal compounds with this structure in the laboratory. Due to their unique crystal geometry, Kagome metals combine unique electronic, magnetic and superconducting properties, making them promising for future quantum technologies.

Professor Ronny Thomale of the Würzburg-Dresden Cluster of Excellence ct.qmat – Complexity and Topology in Quantum Matter, and Chair of Theoretical Physics at the University of Würzburg (JMU) provided important information in this group of tools with his first predictions of theory. Recent research published in Nature suggests that these materials could lead to new electronic components, such as superconducting diodes.

Breakthrough in Superconductivity

In a paper published online on February 16, 2023, Professor Thomale’s team proposed that a unique type of superconductivity can be observed in Kagome metals, with Cooper pairs distributed in a wave-like manner through among the sublattices. Each “star point” has a different number of Cooper pairs. Thomale’s theory has now been directly confirmed for the first time in an international trial, causing a worldwide sensation. This overturns the earlier assumption that Kagome’s metal can accommodate uniformly distributed Cooper pairs.

Cooper pairs – named after the physicist Leon Cooper – are formed at very low temperatures by electrons, and are essential for superconductivity. Working together, they can create a quantum state, and can travel through Kagome’s superconductor without resistance.

Quantum Phenomena and Research Advances

“Initially, our research on Kagome metals such as potassium vanadium antimony (KV3Sb5) focused on the quantum effects of individual electrons, which, although not superconducting, can exhibit behavior like of waves in information,” explains Thomale. “After conducting experiments to confirm our first theory of electron behavior by detecting strong charge waves two years ago, we tried to find additional quantum phenomena at very low temperatures “This led to the discovery of Kagome’s superconductor. However, worldwide research into Kagome’s materials is still in its infancy,” said Thomale.

Transmitting Wave Motion

“Quantum physics is familiar with the phenomenon of pair-density waves — a special type of superconducting condensate. As we all know from cooking, when steam cools, it condenses and turns into liquid. The same thing happens at Kagome’s facilities. At a very low temperature -193 degrees Celsiuselectrons rearrange and distribute in material waves. This has been known since the discovery of strong charge waves, “explains doctoral student Hendrik Hohmann, who participates in the study together with his colleague Matteo Dürrnagel. “When the temperature drops to -272 degrees (approx a full note), the electrons pair up. These Cooper pairs combine to form a quantum liquid that also propagates waves through the material, enabling superconductivity without resistance. Therefore, this wave-like distribution is transferred from electrons to Cooper pairs.”

Previous research on Kagome metal has shown both superconductivity and the spatial distribution of Cooper pairs. A surprising new discovery is that these pairs can be distributed not only evenly, but also in the same way as waves in atomic sublattices, something called “sublattice-modulated superconductivity.” Dürrnagel adds: “The presence of two peak waves in KV3Sb5 is ultimately due to the wave-like electron distribution at a temperature of 80 degrees above superconductivity. This combination of quantum effects has great potential.”

The ct.qmat researchers are now looking for Kagome metals where the Cooper pairs show spatial modulation without the energy waves that precede superconductivity. Promising candidates are already being studied.

Josephson’s Nobel Prize-winning effect enables success

The experiment, which first directly detects Cooper pairs distributed in wave-like patterns in Kagome metal, was developed by Jia-Xin Yin at the Southern University of Science and Technology in Shenzhen. , China. It used a scanning microscope with a high point that could look directly at the Cooper pairs. The design of this point, ends with one atombased on the Nobel Prize-winning Josephson effect. Now superconducting passes between the point of the microscope and the sample, which enables the direct measurement of the Cooper distribution.

“The latest findings are another important step towards efficient quantum materials. Although these effects are currently only seen at the atomic level, once Kagome superconductivity can be achieved on a macroscopic scale, new superconducting materials will And this is what motivates our basic research,” says Professor Thomale.

Pioneering Superconducting Technologies

Although the world’s longest cable has been installed in Munich, intensive research is being done on superconducting electronics. The first superconducting diodes have already been made in the laboratory, but they rely on a combination of different superconducting materials. On the other hand, Kagome’s unique superconductors, with their inherent structure of Cooper pairs, act like diodes themselves, offering exciting possibilities for superconducting electronics and lossless circuits.

References:

“Chiral kagome superconductivity modulations with residual Fermi arcs” by Hanbin Deng, Hailang Qin, Guowei Liu, Tianyu Yang, Ruiqing Fu, Zhongyi Zhang, Xianxin Wu, Zhiwei Wang, Youguo Shi, Jinjin Liu, Hongxiong Liu, Wei-Yu Yan Song, Xitong Xu, Yuanyuan Zhao, Mingsheng Yi, Gang Xu, Hendrik Hohmann, Sofie Castro Holbæk, Matteo Dürrnagel, Sen Zhou, Guoqing Chang, Yugui Yao, Qianghua Wang, Zurab Guguchia, Titus Neupert, Mark H Thomas Figure. Jia-Xin Yin, 21 August 2024, Nature.
DOI: 10.1038/s41586-024-07798-y

“Spatially modulated superconductivity in the Kagome Hubbard model” by Tilman Schwemmer, Hendrik Hohmann, Matteo Dürrnagel, Janik Potten, Jacob Beyer, Stephan Rachel, Yi-Ming Wu, Srinivas Raghu, Tobias Müller, Werner Hanke, Ronny Thomale, 20 March 21, , Condensed Matter > Strongly bound electrons.
arXiv:2302.08517

“Sublattice modulated superconductivity in the kagome Hubbard model” by Tilman Schwemmer, Hendrik Hohmann, Matteo Dürrnagel, Janik Potten, Jacob Beyer, Stephan Rachel, Yi-Ming Wu, Srinivas Raghu, Tobias Müller, Werner Hanke and Ronny Thomale, 20 July 24, , Physical Examination B.
DOI: 10.1103/PhysRevB.110.024501