An ordered phase showing remarkable electronic anisotropy in proximity to the superconducting phase is now a hot issue in the field of high-transition-temperature superconductivity. As in the case of copper oxides, superconductivity in iron arsenides competes or coexists with such an ordered phase. Undoped and underdoped iron arsenides have a magnetostructural ordered phase exhibiting stripe-like antiferromagnetic spin order accompanied by an orthorhombic lattice distortion; both the spin order and lattice distortion break the tetragonal symmetry of crystals of these compounds. In this ordered state, anisotropy of in-plane electrical resistivity is anomalous and difficult to attribute simply to the spin order and/or the lattice distortion. Here, we present the anisotropic optical spectra measured on detwinned BaFe2As2 crystals with light polarization parallel to the Fe planes. Pronounced anisotropy is observed in the spectra, persisting up to an unexpectedly high photon energy of about 2 eV. Such anisotropy arises from an anisotropic energy gap opening below and slightly above the onset of the order. Detailed analysis of the optical spectra reveals an unprecedented electronic state in the ordered phase.
Hidden Phases Revealed at the Surface of Double-Layered Sr3(Ru1-xMnx)2O7
双层Sr 3Ru 2 O 7已经收到了惊人的考虑，因为它表现出过多的外来相时，扰动。随着压力、磁场或掺杂的应用，新相出现。在这里，我们表明，创建一个表面是一种替代和有效的方式来揭示隐藏的阶段，是从那些在散装不同的调查Sr 3（Ru 1-xMnx）2 O 7的表面特性。在RuO 6八面体倾斜畸变的驱动下，Sr 3Ru 2 O 7的表面比体相金属性更弱。相反，由于Mn掺杂的倾斜消失和增强的旋转，Sr 3（Ru0.84Mn0.16）2 O 7的表面是金属的，而体是绝缘的。我们的结果表明，在表面的电子和结构的性质是密切耦合的，并符合准二维字符。
Electronic Phase Propagation Speed in BaFe$_2$As$_2$ Revealed by Dilatometry
International Center for Quantum Materials, Peking University（北京大学量子材料中心）；Hefei National Laboratory（合肥国家实验室）；Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所北京凝聚态物理国家研究中心）
