scholarly journals Nematic state stabilized by off-site Coulomb interaction in iron-based superconductors

2015 ◽  
Vol 92 (8) ◽  
Author(s):  
Xiao-Jun Zheng ◽  
Zhong-Bing Huang ◽  
Da-Yong Liu ◽  
Liang-Jian Zou
Keyword(s):  
Coulomb Interaction ◽  
Iron Based Superconductors ◽  
Nematic State ◽  
Iron Based

scholarly journals Novel electronic nematicity in heavily hole-doped iron pnictide superconductors

2020 ◽  
Vol 117 (12) ◽  
pp. 6424-6429 ◽  
Author(s):  
Kousuke Ishida ◽  
Masaya Tsujii ◽  
Suguru Hosoi ◽  
Yuta Mizukami ◽  
Shigeyuki Ishida ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Rotational Symmetry ◽  
Quantum Liquid ◽  
Iron Based Superconductors ◽  
Iron Pnictide ◽  
Tetragonal Lattice ◽  
Nematic State ◽  
Nematic Director ◽  
Iron Based ◽  
Electronic Nematicity

Electronic nematicity, a correlated state that spontaneously breaks rotational symmetry, is observed in several layered quantum materials. In contrast to their liquid-crystal counterparts, the nematic director cannot usually point in an arbitrary direction (XY nematics), but is locked by the crystal to discrete directions (Ising nematics), resulting in strongly anisotropic fluctuations above the transition. Here, we report on the observation of nearly isotropic XY-nematic fluctuations, via elastoresistance measurements, in hole-doped Ba1−xRbxFe2As2iron-based superconductors. While forx=0, the nematic director points along the in-plane diagonals of the tetragonal lattice, forx=1, it points along the horizontal and vertical axes. Remarkably, for intermediate doping, the susceptibilities of these two symmetry-irreducible nematic channels display comparable Curie–Weiss behavior, thus revealing a nearly XY-nematic state. This opens a route to assess this elusive electronic quantum liquid-crystalline state.

Nematic Electronic Structure in the “Parent” State of the Iron-Based Superconductor Ca(Fe1–xCox)2As2

Science ◽  
2010 ◽  
Vol 327 (5962) ◽  
pp. 181-184 ◽  
Author(s):  
T.-M. Chuang ◽  
M. P. Allan ◽  
Jinho Lee ◽  
Yang Xie ◽  
Ni Ni ◽  
...  
Keyword(s):  
Electronic Structure ◽  
High Temperature Superconductivity ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Iron Based Superconductors ◽  
Bulk Properties ◽  
Quasiparticle Interference ◽  
Parent State ◽  
Nematic State ◽  
Iron Based

The mechanism of high-temperature superconductivity in the newly discovered iron-based superconductors is unresolved. We use spectroscopic imaging–scanning tunneling microscopy to study the electronic structure of a representative compound CaFe1.94Co0.06As2 in the “parent” state from which this superconductivity emerges. Static, unidirectional electronic nanostructures of dimension eight times the inter–iron-atom distance aFe-Fe and aligned along the crystal a axis are observed. In contrast, the delocalized electronic states detectable by quasiparticle interference imaging are dispersive along the b axis only and are consistent with a nematic α2 band with an apparent band folding having wave vector q≅±22π/8aFe-Fe along the a axis. All these effects rotate through 90 degrees at orthorhombic twin boundaries, indicating that they are bulk properties. As none of these phenomena are expected merely due to crystal symmetry, underdoped ferropnictides may exhibit a more complex electronic nematic state than originally expected.

scholarly journals Importance of $${{d}}_{{{xy}}}$$ orbital and electron correlation in iron-based superconductors revealed by phase diagram for 1111-system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tsuyoshi Kawashima ◽  
Shigeki Miyasaka ◽  
Hirokazu Tsuji ◽  
Takahiro Yamamoto ◽  
Masahiro Uekubo ◽  
...  
Keyword(s):  
Electron Correlation ◽  
Weak Coupling ◽  
Structural Parameters ◽  
Structural Flexibility ◽  
Superconducting Transition ◽  
Iron Based Superconductors ◽  
Wide Range ◽  
Band Filling ◽  
Iron Based ◽  
Correlation Strength

AbstractThe structural flexibility at three substitution sites in LaFeAsO enabled investigation of the relation between superconductivity and structural parameters over a wide range of crystal compositions. Substitutions of Nd for La, Sb or P for As, and F or H for O were performed. All these substitutions modify the local structural parameters, while the F/H-substitution also changes band filling. It was found that the superconducting transition temperature $$T_{\text{c}}$$ T c is strongly affected by the pnictogen height $$h_{Pn}$$ h Pn from the Fe-plane that controls the electron correlation strength and the size of the $$d_{xy}$$ d xy hole Fermi surface (FS). With increasing $$h_{Pn}$$ h Pn , weak coupling BCS superconductivity switches to the strong coupling non-BCS one where electron correlations and the $$d_{xy}$$ d xy hole FS may be important.

scholarly journals In-plane electronic anisotropy resulted from ordered magnetic moment in iron-based superconductors

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
S.-F. Wu ◽  
W.-L. Zhang ◽  
V. K. Thorsmølle ◽  
G. F. Chen ◽  
G. T. Tan ◽  
...  
Keyword(s):  
Magnetic Moment ◽  
Iron Based Superconductors ◽  
Iron Based
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