Orbital Order and Spontaneous Orthorombicity in Iron Pnictides
Orbital Order and Spontaneous Orthorombicity in Iron Pnictides
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发表时间：
2011-03
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通讯作者：
Rajiv R. P. Singh
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作者：
Rajiv R. P. Singh
铁磷属元素化物族超导体的相图显示了四方晶系到正交晶系的转变，有时与反铁磁相变一致，有时在明显高于反铁磁相变的温度下。非弹性中子散射谱显示交换常数具有很强的空间各向异性。最近在机械解孪晶样品中的光电子能谱测量显示了铁的dxz和dyz轨道不相等的轨道占据和显著不同的光谱的明确证据。扫描隧道显微镜和传输测量也显示了这些材料的正交性。我们讨论了一个简单的微观图片耦合自旋和轨道自由度的根本原因，这样的各向异性，并讨论在何种程度上，这张照片可以区分自旋挫折引起的伊辛微扰作为这种现象的主要驱动程序。
Phase diagram of the Iron Pnictide families of superconductors show a tetragonal to orthorhombic transition, sometimes coincident with the antiferromagnetic phase transition and sometimes at temperatures clearly above the antiferromagnetic phase transition. Inelastic neutron scattering spectra show exchange constants with strong spatial anisotropy. Recent photoemission measurements in mechanically detwinned samples show clear evidence of unequal orbital occupation and strikingly different spectra for dxz and dyz iron orbitals. Scanning Tunneling Microscopy and transport measurements have also shown substantial orthorhombicity in these materials. We discuss a simple microscopic picture for coupled spin and orbital degrees of freedom as the root cause for such an anisotropy and discuss the extent to which this picture can be distinguished from spin-frustration induced Ising nematic fluctuations as being the dominant driver for this phenomena.