标题： 可调谐的BKT和量子相变在自旋-1/2三角晶格反铁磁体中 显示英文标题

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

摘要： 量子磁性是探索奇异相和相变的最活跃领域之一。 最近合成的Na2BaCo(PO4)2 (NBCP) 是自旋-1/2易轴三角晶格反铁磁体(TLAF)的理想材料体现。 实验证据表明，NBCP 拥有具有巨大磁卡效应的自旋超固态。 也有人提出，施加的磁场 B 可以使系统通过贝瑞金-科斯特里茨-索利斯(BKT)和其他更丰富的量子相变。 然而，这些相变的检测具有挑战性，因为它们在大约60 mK的极低温下开始，这些相变的磁化率测量需要高灵敏度。 在我们新开发的稀释冰箱中的梯度力磁强计的帮助下，我们在B-T相图中构建了磁化率的轮廓图，温度低至30 mK。 这些结果提供了对几种场可调量子相变和自旋超固态BKT熔化的更全面和准确的理解，当它们的巨大磁卡效应凸显出在关注全球氦气短缺情况下亚开尔文制冷的潜在应用时，这一点尤其重要。 显示英文摘要

摘要： 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.