scholarly journals ON d+id DENSITY WAVE AND SUPERCONDUCTING ORDERINGS IN HOLE-DOPED CUPRATES

2013 ◽  
Vol 27 (13) ◽  
pp. 1330008
Author(s):  
PARTHA GOSWAMI ◽  
AJAY PRATAP SINGH GAHLOT ◽  
PANKAJ SINGH
Keyword(s):  
Chemical Potential ◽  
Density Wave ◽  
Mean Field ◽  
Spectral Weight ◽  
Quasi Particle ◽  
Scattering Rate ◽  
Consistent Manner ◽  
Single Particle Excitation ◽  
The Mean ◽  
Competing Orders

The d+id-density wave (chiral DDW) order, at the anti-ferromagnetic wave vector Q = (π, π), is assumed to represent the pseudo-gap (PG) state of a hole-doped cuprate superconductor. The pairing interaction U(k, k′) required for d+id ordering comprises of (Ux2-y2(k, k′), Uxy(k, k′)), where [Formula: see text] and [Formula: see text] with U1 > U2. The d-wave superconductivity (DSC), driven by an assumed attractive interaction of the form [Formula: see text] where V1 is a model parameter, is discussed within the mean-field framework together with the d+id ordering. The single-particle excitation spectrum in the CDDW + DSC state is characterized by the Bogoluibov quasi-particle bands — a characteristic feature of SC state. The coupled gap equations are solved self-consistently together with the equation to determine the chemical potential (μ). With the pinning of the van Hove-singularities close to μ, one is able to calculate the thermodynamic and transport properties of the under-doped cuprates in a consistent manner. The electron specific heat displays non-Fermi liquid feature in the CDDW state. The CDDW and DSC are found to represent two competing orders as the former brings about a depletion of the spectral weight (and Raman response function density) available for pairing in the anti-nodal region of momentum space. It is also shown that the depletion of the spectral weight below Tc at energies larger than the gap amplitude occurs. This is an indication of the strong-coupling superconductivity in cuprates. The calculation of the ratio of the quasi-particle thermal conductivity αxx and temperature in the superconducting phase is found to be constant in the limit of near-zero quasi-particle scattering rate.

scholarly journals A Theoretical Approach to Pseudogap and Superconducting Transitions in Hole-Doped Cuprates

2013 ◽  
Vol 2013 ◽  
pp. 1-26
Author(s):  
Partha Goswami
Keyword(s):  
Excitation Spectrum ◽  
Single Particle ◽  
Momentum Space ◽  
Density Wave ◽  
Mean Field ◽  
Spectral Weight ◽  
Square Lattice ◽  
Cooper Pairs ◽  
Single Particle Excitation ◽  
Competing Orders

We consider a two-dimensional fermion system on a square lattice described by a mean-field Hamiltonian involving the singlet id-density wave (DDW) order, assumed to correspond to the pseudo-gap (PG) state, favored by the electronic repulsion and the coexisting -wave superconductivity (DSC) driven by an assumed attractive interaction within the BCS framework. Whereas the single-particle excitation spectrum of the pure DDW state consists of the fermionic particles and holes over the reasonably conducting background, the coexisting states corresponds to Bogoliubov quasi-particles in the background of the delocalized Cooper pairs in the momentum space. We find that the two gaps in the single-particle excitation spectrum corresponding to PG and DSC, respectively, are distinct and do not merge into one “quadrature” gap if the nesting property of the normal state dispersion is absent. We show that the PG and DSC are representing two competing orders as the former brings about a depletion of the spectral weight available for pairing in the anti-nodal region of momentum space where the superconducting gap is supposed to be the largest. This indicates that the PG state perhaps could not be linked to a preformed pairing scenario. We also show the depletion of the spectral weight below at energies larger than the gap amplitude. This is an important hallmark of the strong coupling superconductivity.

Modification of charge density wave fluctuations by charge perturbations

2002 ◽  
Vol 12 (9) ◽  
pp. 77-78
Author(s):  
S. N. Artemenko
Keyword(s):  
Electric Field ◽  
Linear Response ◽  
Chemical Potential ◽  
Density Wave ◽  
Mean Field ◽  
Phase Fluctuations ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
The Mean ◽  
Field Transition

Spectral density of fluctuations of the CDW phase are calculated taking into account electric field induced by phase fluctuations. The approach based upon the fluctuation-dissipation theorem (FDT) combined with equations of linear response of the CDW conductor is used. Fluctuating electric field is found to suppress fluctuations of the phase, while fluctuations of the electric potential are sizeable. This suggests that transition from the CDW to the normal state (which is usually observed well below the mean-field transition temperature) may he provoked by fluctuations of the chemical potential, rather than by destruction of the CDW coherence between conducting chains due to phase fluctuations.

scholarly journals Locating the critical end point using the linear sigma model coupled to quarks.

2018 ◽  
Vol 172 ◽  
pp. 02003
Author(s):  
Alejandro Ayala ◽  
J. A. Flores ◽  
L. A. Hernández ◽  
S. Hernández-Ortiz
Keyword(s):  
Sigma Model ◽  
Chemical Potential ◽  
Potential Temperature ◽  
Mean Field ◽  
Field Approximation ◽  
Baryon Density ◽  
Linear Sigma Model ◽  
Mean Field Approximation ◽  
End Point ◽  
The Mean

We use the linear sigma model coupled to quarks to compute the effective potential beyond the mean field approximation, including the contribution of the ring diagrams at finite temperature and baryon density. We determine the model couplings and use them to study the phase diagram in the baryon chemical potential-temperature plane and to locate the Critical End Point.

scholarly journals DISORDER INDUCED BCS-BEC CROSSOVER

2012 ◽  
Vol 11 ◽  
pp. 120-126 ◽  
Author(s):  
AYAN KHAN
Keyword(s):  
Order Parameter ◽  
Chemical Potential ◽  
Random Potential ◽  
Mean Field ◽  
Superconducting Order Parameter ◽  
Interesting Issue ◽  
Coupled Equations ◽  
Weak Regime ◽  
The Mean ◽  
Superconducting Fluctuations

Of late, the study of BCS-BEC crossover in the presence of weak random impurity is an interesting issue. In this proceedings we study the effect of this disorder which is included through the Nozières and Smith-Rink theory of superconducting fluctuations. In the weak regime, the random potential leaves an effect on the superconducting order parameter but it spares the chemical potential. Here we present the exact behavior of the mean field quantities as a function of the disorder by self-consistently solving the coupled equations.

THE ROLE OF ANTIKAON CONDENSATES IN THE EQUATION OF STATE OF NEUTRON STARS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1545-1548 ◽  
Author(s):  
F. FERNÁNDEZ ◽  
A. MESQUITA ◽  
M. RAZEIRA ◽  
C. A. Z. VASCONCELLOS
Keyword(s):  
Neutron Stars ◽  
Electric Charge ◽  
Chemical Potential ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Charge Neutrality ◽  
The Mean ◽  
Nucleon Matter

We study the consequences of the presence of a negative electric charge condensate of antikaons in neutron stars using an effective model with derivative couplings. In our formalism, nucleons interact through the exchange of σ, ω and ϱ mesons, in the presence of electrons and muons, to accomplish electric charge neutrality and beta equilibrium. The phase transition to the antikaon condensate was implemented through the Gibbs conditions combined with the mean-field approximation, giving rise to a mixed phase of coexistence between nucleon matter and the antikaon condensate. Assuming neutrino-free matter, we observe a rapid decrease of the electron chemical potential produced by the gradual substitution of electrons by kaons to accomplish electric charge neutrality. The exotic composition of matter in neutron star including antikaon condensation and nucleons can yield a maximum mass of about M ns ~ 1.76 M ⊙.

scholarly journals Finite-Temperature Bose-Einstein Condensation in Interacting Boson System

2019 ◽  
Vol 64 (12) ◽  
pp. 1118
Author(s):  
D. Anchishkin ◽  
I. Mishustin ◽  
O. Stashko ◽  
D. Zhuravel ◽  
H. Stoecker
Keyword(s):  
Chemical Potential ◽  
Bose Condensate ◽  
Mean Field ◽  
Einstein Condensation ◽  
Total Density ◽  
Boson System ◽  
First Order Phase Transition ◽  
The Mean ◽  
Bose Einstein ◽  
First Order Phase

Thermodynamical properties of an interacting boson system at finite temperatures and zero chemical potential are studied within the framework of the Skyrme-like mean-field toy model. It is assumed that the mean field contains both attractive and repulsive terms. Self-consistency relations between the mean field and thermodynamic functions are derived. It is shown that, for sufficiently strong attractive interactions, this system develops a first-order phase transition via the formation of a Bose condensate. An interesting prediction of the model is that the condensed phase is characterized by a constant total density of particles. It is shown that the energy density exhibits a jump at the critical temperature.

Thermal fluctuations in the interface of an inhomogeneous fluid

1982 ◽  
Vol 60 (2) ◽  
pp. 137-153 ◽  
Author(s):  
Luis de Sobrino ◽  
Jože Peternelj
Keyword(s):  
Capillary Wave ◽  
Mean Field Theory ◽  
Mean Field ◽  
Wave Theory ◽  
Thermal Fluctuations ◽  
Van Der Waals Gas ◽  
Inhomogeneous Fluid ◽  
Consistent Manner ◽  
The Mean ◽  
Interface Profile

We use van Kampen's expression for the partition function of a van der Waals gas to investigate the effect of noncritical fluctuations on the interface of an inhomogeneous fluid. Such a procedure combines in a consistent manner the results of mean field theory and of capillary wave theory and, in addition, uncovers contributions due to fluctuations of the interface profile. Although the latter add negligibly to the interfacial width, they result in corrections to the mean field surface tension comparable to those resulting from capillary fluctuations. The effect of the walls in limiting the fluctuations is explicitly taken into account.

FRÖHLICH'S ONE-DIMENSIONAL SUPERCONDUCTOR WITH PARA-FERMI STATISTICS

1994 ◽  
Vol 08 (19) ◽  
pp. 1195-1200 ◽  
Author(s):  
V. L. SAFONOV ◽  
A. V. ROZHKOV
Keyword(s):  
Density Wave ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Wave State ◽  
One Dimensional ◽  
Fermi Statistics ◽  
The Mean ◽  
A Charge ◽  
Dimensional Crystal

The hypothesis that conduction electrons in a one-dimensional crystal obey para-Fermi statistics is discussed. Thermal properties of Fröhlich's model in the mean-field approximation are calculated within the framework of this hypothesis. It is shown that the temperature of the phase transition to a charge density wave state is greater in a system with parastatistics.

scholarly journals Investigation of a CDDW Hamiltonian to Explore Possibility of Magneto-Quantum Oscillations in Electronic Specific Heat of Hole-Doped Cuprates

2010 ◽  
Vol 2010 ◽  
pp. 1-11
Author(s):  
Partha Goswami ◽  
Manju Rani
Keyword(s):  
Specific Heat ◽  
Chemical Potential ◽  
Density Wave ◽  
Mean Field ◽  
Anisotropy Parameter ◽  
Zero Magnetic Field ◽  
Electronic Specific Heat ◽  
Mean Field Model ◽  
Quantum Oscillations ◽  
Disorder Potential

We investigate a chiral d-density wave (CDDW) mean field model Hamiltonian in the momentum space suitable for the hole-doped cuprates, such as YBCO, in the pseudogap phase to obtain the Fermi surface (FS) topologies, including the anisotropy parameter() and the elastic scattering by disorder potential (). For , with the chemical potential eV for 10% doping level and (where eV is the first neighbor hopping), at zero/non-zero magnetic field (), the FS on the first Brillouin zone is found to correspond to electron pockets around antinodal regions and barely visible patches around nodal regions. For , we find Pomeranchuk distortion of FS. We next relate our findings regarding FS to the magneto-quantum oscillations in the electronic specific heat. Since the nodal quasiparticle energy values for are found to be greater than for , the origin of the oscillations for nonzero corresponds to the Fermi pockets around antinodal regions. The oscillations are shown to take place in the weak disorder regime (eV) only.

scholarly journals Non-Hermitian BCS-BEC crossover of Dirac fermions

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Takuya Kanazawa
Keyword(s):  
Chiral Symmetry ◽  
Chemical Potential ◽  
Chiral Symmetry Breaking ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Dirac Fermions ◽  
Coupling Constant ◽  
Dynamical Mass ◽  
The Mean

Abstract We investigate chiral symmetry breaking in a model of Dirac fermions with a complexified coupling constant whose imaginary part represents dissipation. We introduce a chiral chemical potential and observe that for real coupling a relativistic BCS-BEC crossover is realized. We solve the model in the mean-field approximation and construct the phase diagram as a function of the complex coupling. It is found that the dynamical mass increases under dissipation, although the chiral symmetry gets restored if dissipation exceeds a threshold.

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