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.

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 Twofold symmetry of c-axis resistivity in topological kagome superconductor CsV3Sb5 with in-plane rotating magnetic field

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ying Xiang ◽  
Qing Li ◽  
Yongkai Li ◽  
Wei Xie ◽  
Huan Yang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electronic State ◽  
Degrees Of Freedom ◽  
Electron State ◽  
Rotational Symmetry ◽  
Rotating Magnetic Field ◽  
Metal Compounds ◽  
Spin Lattice ◽  
Nematic State ◽  
Iron Based

AbstractIn transition metal compounds, due to the interplay of charge, spin, lattice and orbital degrees of freedom, many intertwined orders exist with close energies. One of the commonly observed states is the so-called nematic electron state, which breaks the in-plane rotational symmetry. This nematic state appears in cuprates, iron-based superconductor, etc. Nematicity may coexist, affect, cooperate or compete with other orders. Here we show the anisotropic in-plane electronic state and superconductivity in a recently discovered kagome metal CsV3Sb5 by measuring c-axis resistivity with the in-plane rotation of magnetic field. We observe a twofold symmetry of superconductivity in the superconducting state and a unique in-plane nematic electronic state in normal state when rotating the in-plane magnetic field. Interestingly these two orders are orthogonal to each other in terms of the field direction of the minimum resistivity. Our results shed new light in understanding non-trivial physical properties of CsV3Sb5.

scholarly journals ELEMENTARY EXCITATIONS DUE TO ORBITAL DEGREES OF FREEDOM IN IRON-BASED SUPERCONDUCTORS

2013 ◽  
Vol 27 (20) ◽  
pp. 1330014 ◽  
Author(s):  
WEI-CHENG LEE ◽  
WEICHENG LV ◽  
HAMOOD Z. ARHAM
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Degrees Of Freedom ◽  
Rotational Symmetry ◽  
Structural Phase ◽  
Iron Based Superconductors ◽  
Elementary Excitations ◽  
Lattice Symmetry ◽  
Iron Based ◽  
Intense Debate

One central issue under intense debate in the study of the iron-based superconductors is the origin of the structural phase transition that changes the crystal lattice symmetry from tetragonal to orthorhombic. This structural phase transition, occurring universally in almost every family of the iron-based superconductors, breaks the lattice C4 rotational symmetry and results in an anisotropy in a number of physical properties. Due to the unique topology of the Fermi surface, both orbital- and spin-based scenarios have been proposed as the driving force. In this review, we focus on theories from the orbital-based scenario and discuss several related experiments. It is pointed out that although both scenarios lead to the same macroscopic phases and are not distinguishable in bulk measurements of the thermodynamic properties, the elementary excitations could be fundamentally different, and provide us with the possibility to resolve this long-standing debate between orbital- and spin-based theories.

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 Emerging symmetric strain response and weakening nematic fluctuations in strongly hole-doped iron-based superconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
P. Wiecki ◽  
M. Frachet ◽  
A.-A. Haghighirad ◽  
T. Wolf ◽  
C. Meingast ◽  
...  
Keyword(s):  
Hole Doping ◽  
Strain Response ◽  
Iron Based Superconductors ◽  
Optimal Doping ◽  
Plane Symmetric ◽  
Nematic Order ◽  
Unconventional Superconductors ◽  
Iron Based ◽  
Electronic Nematicity ◽  
Ordered State

AbstractElectronic nematicity is often found in unconventional superconductors, suggesting its relevance for electronic pairing. In the strongly hole-doped iron-based superconductors, the symmetry channel and strength of the nematic fluctuations, as well as the possible presence of long-range nematic order, remain controversial. Here, we address these questions using transport measurements under elastic strain. By decomposing the strain response into the appropriate symmetry channels, we demonstrate the emergence of a giant in-plane symmetric contribution, associated with the growth of both strong electronic correlations and the sensitivity of these correlations to strain. We find weakened remnants of the nematic fluctuations that are present at optimal doping, but no change in the symmetry channel of nematic fluctuations with hole doping. Furthermore, we find no indication of a nematic-ordered state in the AFe2As2 (A = K, Rb, Cs) superconductors. These results revise the current understanding of nematicity in hole-doped iron-based superconductors.

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.

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