Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling
Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling
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DOI：
10.1103/physrevb.102.045143
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发表时间：
2020-05
影响因子：
3.7
通讯作者：
J. Nasu;M. Naka;S. Ishihara
中科院分区：
文献类型：
--
作者：
J. Nasu;M. Naka;S. Ishihara
研究了自旋轨道耦合（SOC）和磁场对激子绝缘（EI）态的影响。介绍了讨论强关联电子系统中激子凝聚的最小模型--考虑晶场分裂的双轨道Hubbard模型，并利用平均场理论分析了其在强关联极限下的有效哈密顿量.在没有SOC和磁场的情况下，通过增加Hund耦合，基态从能带绝缘态变为EI态。在外加磁场中，磁矩出现在EI状态，该状态与受迫铁磁状态连续相连。另一方面，在SOC的存在下，它们被相边界分开。我们发现在具有小SOC的边界附近的EI相中磁化率强烈增强。这种特殊的行为归因于Hund耦合稳定的高自旋局域态中固有的自旋向列性的低能涨落。本研究不仅揭示了自旋向列性对EI态的影响，而且揭示了自旋向列性量子涨落对EI态的影响。
Effects of the spin-orbit coupling (SOC) and magnetic field on excitonic insulating (EI) states are investigated. We introduce the two-orbital Hubbard model with the crystalline field splitting, which is a minimal model for discussing the exciton condensation in strongly correlated electron systems, and analyze its effective Hamiltonian in the strong correlation limit by using the mean-field theory. In the absence of the SOC and magnetic field, the ground state changes from the nonmagnetic band-insulating state to the EI state by increasing the Hund coupling. In an applied magnetic field, the magnetic moment appears in the EI state, which is continuously connected to the forced ferromagnetic state. On the other hand, in the presence of the SOC, they are separated by a phase boundary. We find that the magnetic susceptibility is strongly enhanced in the EI phase near the boundary with a small SOC. This peculiar behavior is attributed to the low-energy fluctuation of the spin nematicity inherent in the high-spin local state stabilized by the Hund coupling. The present study not only reveals the impact of the SOC for the EI state but also sheds light on the role of quantum fluctuations of the spin nematicity for the EI state.