Quantum magnetism is one of the most active fields for exploring exotic phases and phase transitions. The recently synthesized Na2BaCo(PO4)2 (NBCP) is an ideal material incarnation of the spin-1/2 easy axis triangular lattice antiferromagnet (TLAF). Experimental evidence shows that NBCP hosts the spin supersolid state with a giant magnetocaloric effect. It was also proposed that the applied magnetic field B can drive the system through Berezinskii-Kosterlitz-Thouless (BKT) and other richer quantum phase transitions. However, the detection of these transitions is challenging because they onset at extremely low temperature T at around 60 mK, and the measurement of the magnetic susceptibility of these transitions requires high sensitivity. With the help of our newly developed gradient force magnetometer in a dilution refrigerator, we constructed the contour diagram of the magnetic susceptibility in the B-T phase diagram in T as cold as 30 mK. These results provide a more comprehensive and accurate understanding of the several field-tunable quantum phase transitions and BKT melting of the spin supersolidity, which are especially significant when their giant magnetocaloric effects highlight potential applications for sub-Kelvin refrigeration under concerns about global helium shortages.
@article{arxiv.2411.04755,
title = {Field tunable BKT and quantum phase transitions in spin-1/2 triangular lattice antiferromagnet},
author = {Dechen Zhang and Yuan Zhu and Guoxin Zheng and Kuan-Wen Chen and Qing Huang and Lingxiao Zhou and Yujie Liu and Kaila Jenkins and Aaron Chan and Haidong Zhou and Lu Li},
journal= {arXiv preprint arXiv:2411.04755},
year = {2025}
}
Comments
19 pages, 5 main figures, and 4 figures in the supplement