Department of Physics, Korean Advanced Institute of Science and Technology, Daejun 305-701, Korea.
Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA.
Nat Commun. 2014 Jun 3;5:3988. doi: 10.1038/ncomms4988.
The entanglement of the spin and orbital degrees of freedom through the spin-orbit coupling has been actively studied in condensed matter physics. In several iridium oxide systems, the spin-orbital entangled state, identified by the effective angular momentum jeff, can host novel quantum phases. Here we show that a series of lacunar spinel compounds, GaM4X8 (M=Nb, Mo, Ta and W and X=S, Se and Te), gives rise to a molecular jeff state as a new spin-orbital composite on which the low-energy effective Hamiltonian is based. A wide range of electron correlations is accessible by tuning the bandwidth under external and/or chemical pressure, enabling us to investigate the cooperation between spin-orbit coupling and electron correlations. As illustrative examples, a two-dimensional topological insulating phase and an anisotropic spin Hamiltonian are investigated in the weak and strong coupling regimes, respectively. Our finding can provide an ideal platform for exploring jeff physics and the resulting emergent phenomena.
自旋和轨道自由度通过自旋轨道耦合的纠缠在凝聚态物理中得到了广泛的研究。在几种氧化铱体系中，通过有效角动量 jeff 来识别的自旋轨道纠缠态可以承载新的量子相。在这里，我们表明一系列的空穴尖晶石化合物 GaM4X8（M=Nb、Mo、Ta 和 W，X=S、Se 和 Te）产生了一个分子 jeff 态，作为一个新的自旋轨道复合材料，其低能有效哈密顿量基于此。通过外部和/或化学压力下的带宽调谐，可以实现广泛的电子关联，使我们能够研究自旋轨道耦合和电子关联之间的合作。作为说明性的例子，在弱和强耦合区域分别研究了二维拓扑绝缘相和各向异性自旋哈密顿量。我们的发现为探索 jeff 物理及其产生的涌现现象提供了一个理想的平台。
