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arXiv 1808.06154cond-mat.str-elcond-mat.mtrl-scicond-mat.supr-con
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$d^8$莫特绝缘体中自旋轨道纠缠产生的量子临界性:金刚石晶格反铁磁物质的情况

Emergent quantum criticality from spin-orbital entanglement in $d^8$ Mott insulators: the case of a diamond lattice antiferromagnet

Fei-Ye Li, Gang Chen

摘要:

受近年来Ni基金刚石晶格反铁磁体NiRh $_2$ O $_4$研究的启发,我们从理论上探讨了四面体晶场环境和金刚石晶格莫特绝缘体上具有$3d^8$电子组态的Ni $^{2+}$离子的自旋和轨道物理.局域矩之间的超交换作用通常有利于磁序。由于Ni $^{2+}$离子的特殊电子构型,具有部分填充的上$t_{2g}$能级和完全填充的下$e_g$能级,原子自旋轨道耦合在线性级变得活跃,并且将有利于自旋轨道纠缠单线态,其在单离子极限中具有淬灭的局部矩。因此,自旋-轨道纠缠与超交换竞争,并可能将系统驱动到分离自旋-轨道单线态和磁序的量子临界点。我们进一步探讨了磁场和单轴压力的影响。对磁场的非平凡响应与局部矩的基本自旋轨道结构密切相关。我们讨论了未来的实验,如掺杂和压力,并指出不同的电子组态之间的对应关系。

英文摘要:

Motivated by the recent activities on the Ni-based diamond lattice antiferromagnet NiRh$_2$O$_4$, we theoretically explore on a general ground the unique spin and orbital physics for the Ni$^{2+}$ ions with a $3d^8$ electron configuration in the tetrahedral crystal field environment and on a diamond lattice Mott insulator. The superexchange interaction between the local moments usually favors magnetic orders. Due to the particular electron configuration of the Ni$^{2+}$ ion with a partially filled upper $t_{2g}$ level and a fully filled lower $e_g$ level, the atomic spin-orbit coupling becomes active at the linear order and would favor a spin-orbital-entangled singlet with quenched local moments in the single-ion limit. Thus, the spin-orbital entanglement competes with the superexchange and could drive the system to a quantum critical point that separates the spin-orbital singlet and the magnetic order. We further explore the effects of magnetic field and uniaxial pressure. The non-trivial response to the magnetic field is intimately tied to the underlying spin-orbital structure of the local moments. We discuss the future experiments such as doping and pressure, and point out the correspondence between different electron configurations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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