Nontrivial topology in a Kagome superconductor

Published September 11, 2023

Left: Magnetic torque vs magnetic field, Right: A 0.4mm long sample mounted on a piezoresistive torque magnetometer.

K. Shrestha (West Texas A&M University (WTAMU) & D. Graf (National MagLab)

Kagome is the name given to the traditional Japanese star-like pattern to form baskets. The same geometric pattern can be found in the crystal structure of certain materials and can give rise to frustrated magnetism, charge density waves, superconductivity and topological properties. In a star turn for geometry, the same pattern which has given strength and beauty to weaving for thousands of years is used by nature to produce materials with complex electronic behavior.

What did scientists discover?

The application of extremely high DC magnetic fields up to 45T allowed the observation of many quantum oscillation frequencies in the magnetization of KV₃Sb₅ that had not been observed previously. In addition, researchers could track the angular variation of most of the frequencies to unambiguously confirm the quasi-2D nature of the Fermi surface Berry phase calculations, obtained by constructing the Landau level fan diagram, confirmed the non-trivial band topology in KV₃Sb₅. Furthermore, calculations show that the Fermi surface undergoes severe reconstruction due to charge density wave ordering in KV₃Sb₅ and frequency values calculated from theory are consistent with the experimental results.

Why is this important?

Topological materials possess charge carriers with a much higher mobility than is found in normal conductors. Fully understanding their electronic properties is crucial to the design and development of electronic devices utilizing these materials. The detailed knowledge of the Fermi surface obtained through this research will improve our understanding of the fundamental physics of the non-trivial topology, charge density wave, and superconductivity in KV₃Sb₅.

Who did the research?

K. Shrestha¹, M. Shi², B. Regmi³, T. Nguyen¹, D. Miertschin¹,K. Fan², L. Z. Deng⁴, N. Aryal⁵, S.-G. Kim³, D. E. Graf^6,7, X. Chen² and C. W. Chu ^4,8

¹West Texas A&M University (WTAMU); ²University of Science & Technology of China; ³Mississippi State University; ⁴University of Houston; ⁵Brookhaven National Lab; ⁶Florida State University; ⁷National MagLab; ⁸Lawrence Berkeley National Lab

Why did they need the MagLab?

To observe the quantum oscillations needed to map the Fermi surface of this material, it is necessary to cool the sample to temperatures as low as 0.32K and apply very high magnetic fields (well above 20T). Indeed, the 45T hybrid magnet exponentially amplifies these quantum oscillations. It is only available at the MagLab and is readily accessible through the MagLab’s user program.

Details for scientists

View or download the expert-level Science Highlight, Nontrivial topology in a kagome superconductor (KV₃Sb₅) probed by torque magnetometry up to 45T
Read the full-length publication, High quantum oscillation frequencies and nontrivial topology in kagome superconductor KV₃Sb₅ probed by torque magnetometry up to 45 T, in Physical Review B

Funding

This research was funded by the following grants: K. Shrestha, T. Nguyen, D. Miertschin (Killgore Research Center at WTAMU, Welch #AE-0025); G.S. Boebinger (NSF DMR-2128556)

For more information, contact Tim Murphy.