Li Qing, Cao Guixin, Okamoto Satoshi, Yi Jieyu, Lin Wenzhi, Sales Brian C, Yan Jiaqiang, Arita Ryotaro, Kuneš Jan, Kozhevnikov Anton V, Eguiluz Adolfo G, Imada Masatoshi, Gai Zheng, Pan Minghu, Mandrus David G
1] Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA [2] Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China [3].
Sci Rep. 2013 Oct 29;3:3073. doi: 10.1038/srep03073.
Particularly in Sr2IrO4, the interplay between spin-orbit coupling, bandwidth and on-site Coulomb repulsion stabilizes a J(eff) = 1/2 spin-orbital entangled insulating state at low temperatures. Whether this insulating phase is Mott- or Slater-type, has been under intense debate. We address this issue via spatially resolved imaging and spectroscopic studies of the Sr2IrO4 surface using scanning tunneling microscopy/spectroscopy (STM/S). STS results clearly illustrate the opening of an insulating gap (150 ~ 250 meV) below the Néel temperature (TN), in qualitative agreement with our density-functional theory (DFT) calculations. More importantly, the temperature dependence of the gap is qualitatively consistent with our DFT + dynamical mean field theory (DMFT) results, both showing a continuous transition from a gapped insulating ground state to a non-gap phase as temperatures approach TN. These results indicate a significant Slater character of gap formation, thus suggesting that Sr2IrO4 is a uniquely correlated system, where Slater and Mott-Hubbard-type behaviors coexist.
特别是在Sr2IrO4中，自旋轨道耦合、带宽和在位库仑排斥之间的相互作用在低温下稳定了J(eff) = 1/2的自旋轨道纠缠绝缘态。这个绝缘相是莫特型还是斯莱特型，一直是激烈争论的焦点。我们通过使用扫描隧道显微镜/光谱（STM/S）对Sr2IrO4表面进行空间分辨成像和光谱研究来解决这个问题。扫描隧道谱（STS）结果清楚地表明，在奈尔温度（TN）以下出现了一个绝缘能隙（150~250毫电子伏特），这与我们的密度泛函理论（DFT）计算结果在定性上是一致的。更重要的是，能隙的温度依赖性与我们的DFT + 动态平均场理论（DMFT）结果在定性上是一致的，两者都表明随着温度接近TN，从带隙绝缘基态到无隙相的连续转变。这些结果表明能隙形成具有显著的斯莱特特征，因此表明Sr2IrO4是一个独特的关联系统，其中斯莱特和莫特 - 哈伯德型行为共存。
