AI 中文总结
本研究通过磁场下拉曼光谱发现Ca$_2$RuO$_4$中存在由面外磁场驱动的非互易磁性一级相变，伴随磁起源模式和声子-希格斯模式耦合改变，且不破坏偶极反铁磁序，表明出现新的四极场控态。
AI 中文摘要
由于强电子关联、磁弹性相互作用和大自旋轨道耦合的相互作用，Ca$_2$RuO$_4$的磁性行为代表了一个独特的谜题。在低温下，出现一种反常的莫特绝缘态，其特征是复杂的反铁磁序，伴随磁矩的集体振幅激发，该激发已被讨论为与希格斯模式类似。我们在此报告了由沿Ca$_2$RuO$_4$晶体学$c$轴的面外磁场驱动的磁性一级相变的证据。磁场中的拉曼测量揭示了磁起源模式的出现，以及声子与希格斯振幅模式之间耦合的伴随改变。这两个拉曼特征均以磁场中的非互易磁滞为特征。令人惊讶的是，观察到的相变不影响面内磁振子的拉曼散射，表明偶极反铁磁序得以保留。这与新的四极场控态的出现一致，其涨落结构可触发晶格与磁性希格斯模式之间的杂化，从而导致观察到的拉曼特征。
英文摘要
The magnetic behavior of Ca$_2$RuO$_4$ represents a unique puzzle due to the interplay of strong electronic correlations, magneto-elastic interactions, and large spin-orbit coupling. At low temperatures, an anomalous Mott insulating state emerges, characterized by a complex antiferromagnetic order with a collective amplitude excitation of the magnetic moment which has been discussed in analogy with the Higgs mode. We report here evidence of a magnetic first-order phase transition driven by an out-of-plane magnetic field along the crystallographic $c$-axis of Ca$_2$RuO$_4$. Raman measurements in magnetic field reveal the emergence of mode of magnetic origin and a concomitant modification of the coupling between a phonon and the Higgs amplitude mode. Both the Raman features are characterized by a non-reciprocal hysteresis in magnetic field. Surprisingly, the observed phase transition does not affect the Raman scattering from the in-plane magnons, indicating that the dipolar antiferromagnetic order is preserved. This is consistent with the onset of a new quadrupolar field-controlled state, whose fluctuations structure can trigger an hybridization between the lattice and the magnetic Higgs mode resulting in the observed Raman features.
Comments26 pages, 14 figures
