Sr2IrO4中Slater金属-绝缘体转变的微观和光谱证据
Microscopic and Spectroscopic Evidence for a Slater Metal-Insulator Transition in Sr2IrO4
摘要：
层状5d过渡金属氧化物（TMOs）由于其自旋轨道耦合、带宽和在位库仑排斥等特性，近年来引起了人们极大的兴趣。在Sr 2 IrO 4中，这种相互作用在费米能级附近打开了一个能隙，并在低温下稳定了Jeff=1/2的自旋轨道纠缠绝缘态。这种金属绝缘转变（MIT）是Mott型（电子相关驱动）还是Slater型（磁序驱动）一直存在激烈的争论。我们解决这个问题，通过空间分辨成像和光谱研究的Sr 2 IrO 4表面使用扫描隧道显微镜/光谱（STM/S）。STS的结果清楚地说明了开放的（~150-250 meV）的绝缘间隙在低温下，在定性与我们的密度泛函理论（DFT）的计算。更重要的是，测得的温度依赖性的间隙宽度加上我们的DFT+动态平均场论（DMFT）的结果强烈支持斯莱特型MIT的情况下Sr 2 IrO 4。STS数据进一步揭示了一个赝能隙结构以上的尼尔温度，推测与反铁磁波动的存在。
英文摘要：
Layered 5d transition metal oxides (TMOs) have attracted significant interest in recent years because of the rich physical properties induced by the interplay between spin-orbit coupling, bandwidth and on-site Coulomb repulsion. In Sr2IrO4, this interplay opens a gap near the Fermi energy and stabilizes a Jeff=1/2 spin-orbital entangled insulating state at low temperatures. Whether this metal-insulating transition (MIT) is Mott-type (electronic-correlation driven) or Slater-type (magnetic-order driven) 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). The STS results clearly illustrate the opening of the (~150-250 meV) insulating gap at low temperatures, in qualitative agreement with our density-functional theory (DFT) calculations. More importantly, the measured temperature dependence of the gap width coupled with our DFT+dynamical mean field theory (DMFT) results strongly support the Slater-type MIT scenario in Sr2IrO4. The STS data further reveal a pseudogap structure above the Neel temperature, presumably related to the presence of antiferromagnetic fluctuations.
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