scholarly journals Intertwined Vestigial Order in Quantum Materials: Nematicity and Beyond

2019 ◽  
Vol 10 (1) ◽  
pp. 133-154 ◽  
Author(s):  
Rafael M. Fernandes ◽  
Peter P. Orth ◽  
Jörg Schmalian
Keyword(s):  
Order Parameter ◽  
Cuprate Superconductors ◽  
Primary Phase ◽  
Nematic Order ◽  
Unconventional Superconductors ◽  
Underlying Principle ◽  
Microscopic Models ◽  
Quantum Materials ◽  
Component Order

A hallmark of the phase diagrams of quantum materials is the existence of multiple electronic ordered states, which, in many cases, are not independent competing phases, but instead display a complex intertwinement. In this review, we focus on a particular realization of intertwined orders: a primary phase characterized by a multi-component order parameter and a fluctuation-driven vestigial phase characterized by a composite order parameter. This concept has been widely employed to elucidate nematicity in iron-based and cuprate superconductors. Here we present a group-theoretical framework that extends this notion to a variety of phases, providing a classification of vestigial orders of unconventional superconductors and density waves. Electronic states with scalar and vector chiral order, spin-nematic order, Ising-nematic order, time-reversal symmetry-breaking order, and algebraic vestigial order emerge from one underlying principle. The formalism provides a framework to understand the complexity of quantum materials based on symmetry, largely without resorting to microscopic models.

scholarly journals Vibronic Mechanism of High Tc Superconductivity

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3266-3270 ◽  
Author(s):  
M. Tachiki ◽  
T. Egami ◽  
M. Machida
Keyword(s):  
Transition Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Attractive Interaction ◽  
Low Frequencies ◽  
High Tc ◽  
Eliashberg Theory ◽  
Bond Stretching ◽  
Vibronic Effect

When phonons strongly mix with electron charge fluctuations with low frequencies, the phonon mediated attractive interaction between electrons is strongly enhanced. The occurrence of the mixing has been indicated by the neutron scattering experimental results that the dispersion of the in-plane Cu–O bond-stretching mode in the high Tc cuprate superconductors is strongly softened near the zone boundary. We propose that the phonon mediated attractive interaction strongly enhanced by the vibronic effect can form a basis for the phonon mechanism of high temperature superconductivity. With the Eliashberg theory and with the electronic structure determined by ARPES and the electronic dielectric function obtained by the softened dispersion of the in-pane Cu–O stretching mode, we calculated the transition temperature and the order parameter at the transition temperature. The order parameter is of the d(x2-y2) symmetry and the transition temperature is well in excess of 100 K.

Unrelated BCS-like pairing pseudogap and critical superconducting transition temperature in various cuprate compounds

2018 ◽  
Vol 32 (18) ◽  
pp. 1850195
Author(s):  
S. Dzhumanov ◽  
E. X. Karimboev ◽  
Sh. S. Djumanov
Keyword(s):  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
Energy Gap ◽  
Characteristic Temperature ◽  
Superconducting Order Parameter ◽  
Superconducting Transition ◽  
Gap Formation ◽  
Arpes Data

The smooth evolution of the energy gap observed in the tunneling and angle-resolved photoemission spectra (ARPES) of high-[Formula: see text] cuprates with lowering the temperature from a pseudogap state above the critical temperature [Formula: see text] to a superconducting state below [Formula: see text], has been poorly interpreted as the evidence that the pseudogap must have the same origin as the superconducting order parameter, and therefore, must be related to [Formula: see text]. We argue that such an explanation of the tunneling gap and ARPES data is misleading. We show that the BCS-like energy gap (or pseudogap) opening in the electronic excitation spectrum of underdoped-to-overdoped cuprates at a characteristic temperature [Formula: see text] and the true superconducting order parameter appearing only at [Formula: see text] are unrelated. The superconducting phenomenon in unconventional cuprate superconductors is fundamentally different from the BCS-like pairing of fermionic quasiparticles, and the superconducting transition temperature [Formula: see text] is not determined by the BCS-like gap formation. The unusual superconducting order parameter in these high-[Formula: see text] materials appears at [Formula: see text] and coexists with the BCS-like gap (or pseudogap) below [Formula: see text].

scholarly journals Momentum Dependence of the Nematic Order Parameter in Iron-Based Superconductors

2019 ◽  
Vol 123 (6) ◽  
Author(s):  
H. Pfau ◽  
S. D. Chen ◽  
M. Yi ◽  
M. Hashimoto ◽  
C. R. Rotundu ◽  
...  
Keyword(s):  
Order Parameter ◽  
Momentum Dependence ◽  
Iron Based Superconductors ◽  
Nematic Order ◽  
Iron Based

The Physical and Molecular Properties of New Low Melting Nematics with Negative Dielectric Anisotropy

1999 ◽  
Vol 54 (6-7) ◽  
pp. 448-452 ◽  
Author(s):  
R. Dąbrowski ◽  
J. Jadżyna ◽  
J. Dziaduszek ◽  
Z. Stolarz ◽  
G. Czechowski ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Physical Properties ◽  
Temperature Dependence ◽  
Carboxylic Acids ◽  
Order Parameter ◽  
Room Temperature ◽  
Dielectric Anisotropy ◽  
Molecular Dipole ◽  
Nematic Order ◽  
Moment Vector

Abstract The paper presents some basic physical properties (static electric permittivities, refraction indices, density and viscosity) of 2-chloro-4-n’-alkylphenyl esters of 4-n-alkylbicyclo[2,2,2] octane-1-carboxylic acids (n’=7, n = 5 and 7) which are, at room temperature, nematics with a negative dielectric an-isotropy. On the basis of temperature dependence of the principal static permittivities ε‖(T) and e⊥(T) of the nematics, using the Maier-Meier equations, the angle between the dipole moment vector and the long axis of mesogenic molecules, the apparent molecular dipole moment square pl μ2app(T), and the nematic order parameter S(T) were determined.

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