13 research outputs found
Non - Fermi Liquid Behavior in Fluctuating Gap Model: From Pole to Zero of the Green's function
We analyze non - Fermi liquid (NFL) behavior of fluctuating gap model (FGM)
of pseudogap behavior in both 1D and 2D. We discuss in detail quasiparticle
renormalization (Z - factor), demonstrating a kind of "marginal" Fermi liquid
or Luttinger liquid behavior and topological stability of the "bare" Fermi
surface (Luttinger theorem). In 2D case we discuss effective picture of Fermi
surface "destruction" both in "hot spots" model of dielectric (AFM, CDW)
pseudogap fluctuations, as well as for qualitatively different case of
superconducting d - wave fluctuations, reflecting NFL spectral density behavior
and similar to that observed in ARPES experiments on copper oxides.Comment: 11 pages, 8 figure
Origin of "hot-spots" in the pseudogap regime of Nd(1.85)Ce(0.15)CuO(4): LDA+DMFT+Sigma_k study
Material specific electronic band structure of the electron-doped high-Tc
cuprate Nd(1.85)Ce(0.15)CuO(4) (NCCO) is calculated within the pseudo gap
regime, using the recently developed generalized LDA+DMFT+Sigma_k scheme.
LDA/DFT (density functional theory within local density approximation) provides
model parameters (hopping integral values, local Coulomb interaction strength)
for the one-band Hubbard model, which is solved by DMFT (dynamical mean-field
theory). To take into account pseudogap fluctuations LDA+DMFT is supplied with
"external" k-dependent self-energy Sigma_k, which describes interaction of
correlated conducting electrons with non-local Heisenberg-like
antiferromagnetic (AFM) spin fluctuations responsible for pseudo gap formation.
Within this LDA+DMFT+Sigma_k approach we demonstrate the formation of
pronounced "hot-spots" on the Fermi surface (FS) map in NCCO, opposite to our
recent calculations for Bi(2)Sr(2)CaCu(2)O(8-d) (Bi2212), which have produced
rather extended region of FS "destruction". There are several physical reasons
for this fact: (i) the "hot-spots" in NCCO are located closer to Brillouin zone
center; (ii) correlation length of AFM fluctuations \xi is larger for NCCO;
(iii) pseudogap potential \Delta is stronger, than in Bi2212. Comparison of our
theoretical data with recent bulk sensitive high-energy angle-resolved
photoemission (ARPES) data for NCCO provides good semiquantitative agreement.
Based on that comparison alternative explanation of the van-Hove singularity at
-0.3 eV is proposed. Optical conductivity both for Bi2212 and NCCO is also
calculated within LDA+DMFT+Sigma_k and compared with experimental results,
demonstrating satisfactory agreement.Comment: 8 pages, 10 figures, 1 tabl
Optical Sum Rule in Strongly Correlated Systems
We discuss the problem of a possible "violation" of the optical sum rule in
the normal (non superconducting) state of strongly correlated electronic
systems, using our recently proposed DMFT+Sigma approach, applied to two
typical models: the "hot - spot" model of the pseudogap state and disordered
Anderson - Hubbard model. We explicitly demonstrate that the general Kubo
single band sum rule is satisfied for both models. However, the optical
integral itself is in general dependent on temperature and characteristic
parameters, such as pseudogap width, correlation strength and disorder
scattering, leading to effective "violation" of the optical sum rule, which may
be observed in the experiments.Comment: 7 pages, 9 figure
Lifshitz quantum phase transitions and Fermi surface transformation with hole doping in high- superconductors
We study the doping evolution of the electronic structure in the normal phase
of high- cuprates. Electronic structure and Fermi surface of cuprates with
single CuO layer in the unit cell like LaSrCuO have been
calculated by the LDA+GTB method in the regime of strong electron correlations
(SEC) and compared to ARPES and quantum oscillations data. We have found two
critical concentrations, and , where the Fermi surface
topology changes. Following I.M. Lifshitz ideas of the quantum phase
transitions (QPT) of the 2.5-order we discuss the concentration dependence of
the low temperature thermodynamics. The behavior of the electronic specific
heat is similar to the Loram and Cooper
experimental data in the vicinity of .Comment: 8 pages, 4 figure