What is the Symmetry of the High-Tc Order Parameter?

1998 ◽  
Vol 12 (29n31) ◽  
pp. 2920-2931 ◽  
Author(s):  
Richard A. Klemm
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Spin Density Wave ◽  
Superconducting Gap ◽  
S Wave ◽  
Orbital Symmetry ◽  
High Tc ◽  
Phase Sensitive

In recent years, there has been a raging controversy regarding the orbital symmetry of the superconducting order parameter (OP) in the high temperature superconductors. Many experiments were interpreted in terms of a dx2-y2-wave OP, but many others were interpreted in terms of a more conventional s-wave OP. We review the problems of both intrinsic and extrinsic natures with the phase-sensitive experiments on YBCO. We further show that the photoemission experiments of the purported superconducting gap in Bi2Sr2CaCu2O 8+δ are entirely consistent with charge- and/or spin-density wave formation in that material. The presence of such density waves greatly complicates the analysis of most experiments. Hence, we conclude that the orbital symmetry of the superconducting OP is still unknown in any of the high temperature superconductors.

scholarly journals Unusual symmetries of the order parameter in cuprates

2020 ◽  
Vol 2 (4) ◽  
pp. 207-212
Author(s):  
Tran Van Luong ◽  
Nguyen Thi Ngoc Nu
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
Cuprate Superconductors ◽  
High Temperature Superconductivity ◽  
Spin Fluctuation ◽  
High Temperature Superconductors ◽  
Coulomb Repulsion ◽  
Bcs Theory ◽  
S Wave ◽  
Wave Symmetry

The BCS superconducting theory, introduced by J. Bardeen, L. Cooper and R. Schriffer in 1957, succeeded in describing and satis-factorily explaining the nature of superconductivity for low-temperature superconductors. However, the BCS theory cannot explain the properties of high-temperature superconductors, discovered by J. G. Bednorz and K. A. Müller in 1986. Although scientists have found a lot of new superconductors and their transition temperatures are constantly increasing, most high-temperature superconductors are found by experiment and so far no theory can fully explain their properties. Many previous studies have suggested that the order parameter in high-temperature copper-based superconductors (cuprate superconductors - cuprates) is in the form of d-wave symmetry, but recent results show that the order parameter has an extended s-wave symmetry (extended s wave). Studying the symmetric forms of order parameters in cuprate can contribute to understanding the nature of high-temperature superconductivity. In this article, the authors present an overview of the development of high-temperature supercon-ductors over the past 30 years and explains unusual symmetries of the order parameter in copper-based superconductors. The com-petition of three coupling mechanisms of electrons in cuprates (the mechanism of coupling through coulomb repulsion, electron-phonon mechanism and spin-fluctuation mechanism) affects the unusual symmetry of the order parameter. The solution of the self-consistency equation in simple cases has been found and the ability to move the phase within the superconducting state has been shown.

NOVEL VORTEX STRIPE PHASE UNDER STRONG MAGNETIC FIELD IN HIGH TEMPERATURE SUPERCONDUCTORS

2005 ◽  
Vol 19 (01n03) ◽  
pp. 9-12 ◽  
Author(s):  
YAN CHEN ◽  
Z. D. WANG ◽  
C. S. TING
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Low Temperature ◽  
Vortex Structure ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Spin Density Wave ◽  
Upper Critical Field ◽  
Stripe Phase ◽  
Stripe Phases

The nature of vortex structure in the mixed state of high-temperature superconductors (HTS) is investigated by solving the Bogoliubov-de Gennes equations with consideration of competition between antiferromagnetic (AF) and d-wave superconductivity (DSC) orders. By varying the applied magnetic field and temperature, the geometry of vortex structure can take two different forms: conventional vortex lattice (triangular or square), or vortex stripe phases where all the order parameters including spin density wave, charge density wave and superconducting order exhibit stripe-like behavior. This novel vortex stripe phases may show up at low temperature and adjacent to upper critical field H c2 Phase diagram of temperature dependence of H c2 will be presented. Our results may shed light on the understanding of the low-temperature H c2 anomalies in some HTS. New experiments are proposed to test our predictions.

scholarly journals NEUTRON SCATTERING SIGNATURE OF d-DENSITY WAVE ORDER IN THE CUPRATES

2001 ◽  
Vol 15 (21) ◽  
pp. 2901-2909 ◽  
Author(s):  
SUDIP CHAKRAVARTY ◽  
HAE-YOUNG KEE ◽  
CHETAN NAYAK
Keyword(s):  
High Temperature ◽  
Neutron Scattering ◽  
Order Parameter ◽  
Recent Experiment ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Polarization Dependence ◽  
Bilayer System ◽  
Pseudogap Phase ◽  
Parameter Theory

An ordered d-density wave (DDW) state has been proposed as an explanation of the pseudogap phase in underdoped high-temperature superconductors. The staggered currents associated with this order have signatures which are qualitatively different from those of ordered spins. We apply the order parameter theory to an orthorhombic bilayer system and show that the expected magnitude as well as the momentum, energy, and polarization dependence of the consequent neutron scattering is consistent with the findings of a recent experiment.

scholarly journals MICROMAGNETISM IN URu2Si2 AND HIGH TEMPERATURE SUPERCONDUCTORS

2002 ◽  
Vol 16 (11n12) ◽  
pp. 1667-1671 ◽  
Author(s):  
ATTILA VIROSZTEK ◽  
KAZUMI MAKI ◽  
BALÁZS DÓRA
Keyword(s):  
High Temperature ◽  
Neutron Scattering ◽  
Spin Density ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Spin Density Wave ◽  
Scattering Data ◽  
Density Waves ◽  
Pseudogap Phase ◽  
Optical Dichroism

It has been proposed, that unconventional density waves (UDW) are possible candidates for systems with hidden order parameter. Unlike in conventional density waves, no periodic modulation of either the charge-, or the spin-density is present in UDW, in spite of a clear thermodynamic signal. Although the unconventional spin density wave (USDW) has been suggested for the "antiferromagnetic" phase of URu2Si2 , the micromagnetism seen by neutron scattering has not been understood. We present here the calculation of the local spin density due to impurities in USDW, which describes quantitatively the neutron scattering data by Amitsuka et al. Further, we propose that the pseudogap phase in high temperature superconductors (HTSC) should also be USDW. Strong evidence for this are the micromagnetism seen by Sidis et al., and the optical dichroism seen by Campuzano et al.

scholarly journals MODIFIED BCS GAP EQUATION FOR JAHN–TELLER DISTORTED HIGH TEMPERATURE SUPERCONDUCTORS

2013 ◽  
Vol 27 (14) ◽  
pp. 1350059 ◽  
Author(s):  
B. K. RAJ ◽  
B. PRADHAN ◽  
G. C. ROUT
Keyword(s):  
High Temperature ◽  
Conduction Band ◽  
Order Parameter ◽  
Lattice Strain ◽  
High Temperature Superconductors ◽  
Model Parameters ◽  
S Wave ◽  
Gap Equation ◽  
Jahn Teller ◽  
Static Lattice

In this communication we report the interplay of the normal electron-phonon (EP) interaction, dynamic Jahn–Teller (DJT) distortion and superconductivity in high temperature superconductors in presence of a static lattice strain. This model consists of a degenerate two orbital band separated by Jahn–Teller (JT) energy modified by the DJT interaction in the conduction band. The superconductivity is assumed to be s-wave type present in the same band. The interaction Hamiltonian is solved by Green's function method and a modified BCS gap equation is obtained with a modified conduction band energy [Formula: see text] and modified BCS order parameter [Formula: see text] with α = 1, 2 designating the two orbitals. This interplay displays some new interesting results which are different from the effect of the static lattice strain on superconducting (SC) order parameter. The interplay is studied by varying the normal EP coupling, the DJT coupling, the SC coupling, the phonon vibration frequency, the phonon wave vector and other model parameters of the system.

scholarly journals The Gap and the Upper Critical FieldHc2as Function of Doping for High-TcCuprates

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Orozco ◽  
R. M. Méndez-Moreno ◽  
M. A. Ortiz
Keyword(s):  
High Temperature ◽  
Critical Field ◽  
Energy Gap ◽  
High Temperature Superconductors ◽  
Upper Critical Field ◽  
Superconducting Gap ◽  
Phonon Interaction ◽  
As Doping ◽  
Electron Phonon Interaction ◽  
Wave Symmetry

The relation between thed-wave superconducting gapΔ0and the specific heat obtained with the Volovik effect is used to determine the upper critical fieldHc2as doping function, for high-temperature superconductors. A two-components model withd-wave symmetry, within the BCS framework, is introduced to describe the superconducting state. Generalized Fermi surface topologies are used in order to increase the density of states at the Fermi level, allowing the high-Tcvalues observed. The electron-phonon interaction is considered the most relevant mechanism for the high-Tccuprates, where the available phonon energy is provided by the half-breathing modes. The energy gap valuesΔ0calculated with this model are introduced to describe the variation of the upper critical fieldHc2as function of doping, forLa2-xSrxCuO4.

Superconducting gap anisotropy caused by a spin-density wave

1988 ◽  
Vol 61 (16) ◽  
pp. 1885-1888 ◽  
Author(s):  
A. W. Overhauser ◽  
L. L. Daemen
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Superconducting Gap ◽  
Gap Anisotropy
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