论文标题
磁性BEC量子临界点处的临界介电敏感性
Critical dielectric susceptibility at a magnetic BEC quantum critical point
论文作者
论文摘要
磁场引起的相变在沮丧的量子量子Paramagnet RB $ _ {2} $ CU $ _ {2} $ MO $ $ $ _3 $ _3 $ o $ _ {12} $通过介电和热量测量单样品上的介电和量热测量。可以澄清的是，粉末样品中先前报道的8〜k的介电异常不是由于所建议的手性自旋液态，而是由于少量的铁电杂质阶段所致。清楚地观察到了副磁和铁电和铁电和磁有序状态之间的两个场诱导的量子相变。结果表明，电偏振是下场（间隙闭合）量子临界点处的二级参数，而是饱和度跃迁处的主要参数。在清楚地识别了后者的磁性玻璃纤维凝结（BEC）性质之后，我们使用介电通道直接测量BEC易感性的临界差异。观察到的幂律行为与三维BEC的理论期望非常吻合。最后，介电数据揭示了该化合物中的磁性预饱和阶段，可能具有异国情调的秩序，具有非常规的断裂对称性。
Magnetic-field-induced phase transitions are investigated in the frustrated gapped quantum paramagnet Rb$_{2}$Cu$_{2}$Mo$_3$O$_{12}$ through dielectric and calorimetric measurements on single-crystal samples. It is clarified that the previously reported dielectric anomaly at 8~K in powder samples is not due to a chiral spin liquid state as has been suggested, but rather to a tiny amount of a ferroelectric impurity phase. Two field-induced quantum phase transitions between paraelectric and paramagnetic and ferroelectric and magnetically ordered states are clearly observed. It is shown that the electric polarization is a secondary order parameter at the lower-field (gap closure) quantum critical point but a primary one at the saturation transition. Having clearly identified the magnetic Bose-Einstein condensation (BEC) nature of the latter, we use the dielectric channel to directly measure the critical divergence of BEC susceptibility. The observed power-law behavior is in very good agreement with theoretical expectations for three-dimensional BEC. Finally, dielectric data reveal magnetic presaturation phases in this compound that may feature exotic order with unconventional broken symmetries.
