Field tunable BKT and quantum phase transitions in spin-1/2 triangular lattice antiferromagnet

Dechen Zhang; Yuan Zhu; Guoxin Zheng; Kuan-Wen Chen; Qing Huang; Lingxiao Zhou; Yujie Liu; Kaila Jenkins; Aaron Chan; Haidong Zhou; Lu Li

doi:10.1016/j.newton.2025.100256

arXiv · 2411.04755

Field tunable BKT and quantum phase transitions in spin-1/2 triangular lattice antiferromagnet

Dechen Zhang·Yuan Zhu·Guoxin Zheng·Kuan-Wen Chen·Qing Huang·Lingxiao Zhou·Yujie Liu·Kaila Jenkins·Aaron Chan·Haidong Zhou·Lu Li

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Abstract

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.

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Dechen Zhang, Yuan Zhu, Guoxin Zheng, Kuan-Wen Chen, Qing Huang, Lingxiao Zhou, Yujie Liu, Kaila Jenkins, Aaron Chan, Haidong Zhou, Lu Li. 2024-11-07. Field tunable BKT and quantum phase transitions in spin-1/2 triangular lattice antiferromagnet. https://doi.org/10.1016/j.newton.2025.100256

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