An effective 1-band model for the cuprate superconductors

Starting from the copper-oxygen Hamiltonian of the CuO2 planes, we derive analytically an extended 1-band Hubbard Hamiltonian for the electrons on copper sites, through a canonical transformation which eliminates the oxygen sites. The model sustains a variety of phases : checkerboard states, stripes, antiferromagnetism, local pairs and mixtures thereof. This approach may be helpful in understanding what is so special about the CuO2 planes, as opposed to other compounds.Comment: Mostly a discussion of the derivation, with a short result presentatio

Conductivity of weakly disordered metals close to a "ferromagnetic" quantum critical point

We calculate analytically the conductivity of weakly disordered metals close to a "ferromagnetic" quantum critical point in the low temperature regime. Ferromagnetic in the sense that the effective carrier potential $V(q,\omega)$, due to critical fluctuations, is peaked at zero momentum $q=0$. Vertex corrections, due to both critical fluctuations and impurity scattering, are explicitly considered. We find that only the vertex corrections due to impurity scattering, combined with the self-energy, generate appreciable effects as a function of the temperature $T$ and the control parameter $a$, which measures the proximity to the critical point. Our results are consistent with resistivity experiments in several materials displaying typical Fermi liquid behavior, but with a diverging prefactor of the $T^2$ term for small $a$.Comment: 9 page

Dominant mode in the cuprates: electronic vs. phononic scenario

We make the case for an electronic origin of the strong mode, recently seen in ARPES experiments, and, in this regard, further discuss the physics of the spin resonance peak

On the Normal State of the High Temperature Superconductors

Based on a Fermi liquid model, we present several results on the normal state of the optimally doped and overdoped cuprate superconductors. Our main result is an analytic demonstration, backed by self-consistent numerical calculations, of the linear in temperature resistivity and linear in 1/(energy) optical conductivity, provided the interacting Fermi liquid has strong peaks in its density of states (van-Hove singularities in 2 dimensions) near the chemical potential. Moreover, we find that the interactions tend to pin these strong peaks close to the chemical potential. This fact compares favorably with experiment on a variety of cuprates. Finally, we show that the above scenario yields naturally the low energy dependence of the experimentally determined susceptibility, without reference to spin waves.Comment: 4 pages, late

Cuprates: experiment vs. quasiparticle theory

Comment on the view of P.W. Anderson on the cuprates, as expressed in the Feb. '00 issue of Physics Today.Comment: Submitted to Physics Toda

A common origin for the resistivity of Cd2_2Re2_2O7_7, the cuprates, and Sr2_2RuO4_4?

We propose an explanation for the temperature dependence of the resistivity of Cd$_2$Re$_2$O$_7$, including the regime above the structural phase transition at $T$=200 $^o$K. The mechanism involved relies on the existence of a strong van Hove singularity close to the Fermi surface, which is evidenced by relevant band structure calculations. The same mechanism has successfully described the $T$-linear resistivity of the cuprates and Sr$_2$RuO$_4$, and the one-particle scattering rate in the former materials, as corroborated by recent experiments. We describe a few predictions for Cd$_2$Re$_2$O$_7$ and Cd$_2$Os$_2$O$_7$

A fermionic superfluid state for many spinful species - II

In a previous report (arxiv:0901.2487), we introduced a new fermionic variational wavefunction, suitable for interacting multi-species systems and sustaining superfluidity. This wavefunction contains a new quantum index. Here we introduce a spin triplet version of this wavefunction, with parallel spin pairs only. We also present a single fermion species wavefunction, which may be relevant for the problem of the BCS to BEC transition.Comment: 4-page report. arXiv admin note: substantial text overlap with arXiv:1007.342

Comment on cond-mat/0007299 by Schofield and Sandeman : inconsistency with experiments

The inconsistency of cond-mat/0007299 and Phys. Rev. B 63 094510 (2001) with ARPES and resistivity data is pointed-out

Dephasing from interactions and spin disorder

We calculate the dephasing rate of the electrons in the presence of interactions and elastic spin disorder scattering. In the frame of a self-consistent diagrammatic treatment, we obtain saturation of the dephasing rate in the limit of zero temperature for spin-orbit disorder in 2 dimensions. This result is in agreement with relevant experiments

Scattering rate, transport and specific heat in a metal close to a quantum critical point : emergence of a robust Fermi liquid picture ?

We calculate the low temperature one-particle scattering rate and the specific heat in a weakly disordered metal close to a quantum critical point. To lowest order in the fluctuation potential, we obtain typical Fermi-liquid results proportional to T^2 and T respectively, with prefactors which diverge as a power law of the control parameter upon approaching the critical point. The Kadowaki-Woods ratio is shown to be independent of the control parameter only for the case of 3-D FM fluctuations. Our work is relevant for experiments on CeCoIn$_5$ and Sr_3Ru_2O_7.Comment: Withdrawn in favour of the paper arxiv:1503.0461