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Jul 20, 2013
07/13

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George Kastrinakis

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In previous reports (arXiv:0901.2487, arXiv:1007.0745), we introduced a new fermionic variational wavefunction, suitable for interacting multi-species systems and sustaining superfluidity. This disentangled wavefunction contains a new quantum index. Here we introduce a general spin triplet version of this wavefunction.

Source: http://arxiv.org/abs/1007.3421v3

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Sep 17, 2013
09/13

by
George Kastrinakis

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

Source: http://arxiv.org/abs/cond-mat/0007251v1

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3.0

Jun 29, 2018
06/18

by
George Kastrinakis

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We calculate analytically the conductivity of weakly disordered metals close to a ferromagnetic quantum critical point in the low temperature regime. 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 $a$ upon approaching the critical point. Our...

Topics: Condensed Matter, Strongly Correlated Electrons

Source: http://arxiv.org/abs/1605.06129

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Sep 18, 2013
09/13

by
George Kastrinakis

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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.

Source: http://arxiv.org/abs/cond-mat/0210223v1

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Sep 22, 2013
09/13

by
George Kastrinakis

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We examine the effects of interface roughness and/or planar impurity doping in a superlattice, in the frame of a weak disorder description. We find that these two types of disorder are equivalent, and that they can be viewed as effective "bulk" disorder, with anisotropic diffusion coefficients. Our results offer quantitative insight to transport properties of multilayers and devices, which contain inadvertently structural disorder at the interfaces.

Source: http://arxiv.org/abs/cond-mat/0111553v1

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Jul 20, 2013
07/13

by
George Kastrinakis

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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.

Source: http://arxiv.org/abs/1007.0745v3

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Sep 22, 2013
09/13

by
George Kastrinakis

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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...

Source: http://arxiv.org/abs/cond-mat/0111166v1

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Sep 23, 2013
09/13

by
George Kastrinakis

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We present a model for the metal-insulator transition in 2D, observed in the recent years. Our starting point consists of two ingredients only, which are ubiquitous in the experiments: Coulomb interactions and weak disorder spin-orbit scattering (coming from the interfaces of the heterostructures in question). In a diagramatic approach, we predict the existence of a characteristic temperature $T_o=T_o(n,\omega_H)$, $n$ being the density of carriers, and $\omega_H$ the Zeeman energy, below which...

Source: http://arxiv.org/abs/cond-mat/0109239v3

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Sep 23, 2013
09/13

by
George Kastrinakis

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We calculate the quasiparticle scattering rate in the superconducting state of the overdoped cuprates, in the context of the Eliashberg formalism for a Fermi liquid with strong van Hove singularities close to the chemical potential. For a $d_{x^2-y^2}$ superconducting gap, we demonstrate analytically that the scattering rate is linear in the maximum of temperature or energy, but with different intercepts and momentum dependence. We discuss our results in view of angle-resolved photoemission...

Source: http://arxiv.org/abs/cond-mat/0312043v2

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Sep 18, 2013
09/13

by
George Kastrinakis

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At low temperature and for finite spin scattering in a weakly disordered metal, for a certain value, predicted from our theory, of the material-dependent paramagnon interaction, the total conductivity becomes highly sensitive to the orbital effects of a finite magnetic field. As a consequence, positive giant magnetoresistance and giant corrections to the Hall coefficient arise. We obtain very good agreement between this theory and recent positive giant magnetoresistance experiments, while...

Source: http://arxiv.org/abs/cond-mat/9509073v3

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Sep 18, 2013
09/13

by
George Kastrinakis

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We study superconductivity in multilayer copper oxides, in the frame of a realistic microscopic formulation. Solving the full temperature dependent BCS gap equations, we obtain a maximum in the transition temperature Tc for M=3 or 4 CuO2 layers in the unit cell for appropriate values of the interlayer tunneling (negative pair tunneling), and via the consideration of the doping imbalance between the inner and outer layers. This is the ubiquitous experimental result for Ca intercalated copper...

Source: http://arxiv.org/abs/0809.2656v5

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Sep 18, 2013
09/13

by
George Kastrinakis

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This paper treats a number of issues of the cuprates, ranging from the spin resonance peak and the linear one-particle scattering rate to the superconducting transition, in the frame of a Fermi liquid model. Recent ARPES expts. by Valla et al., Science vol. 285, 2110 (1999), and e-print cond-mat/0003407, directly support the linearity of the one-particle scattering rate everywhere in the Brillouin zone we obtained here. We show that the origin of this linearity is the strong linear in energy...

Source: http://arxiv.org/abs/cond-mat/0005485v2

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10.0

Jun 27, 2018
06/18

by
George Kastrinakis

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We calculate analytically the low temperature quasi-particle scattering rate, the conductivity, and the specific heat in weakly disordered metals close to a quantum critical point, via the use of a proper fluctuation potential $V(q,\omega)$ between the quasi-particles. We obtain typical Fermi liquid results proportional to $T^2$ and $T$ respectively, with prefactors which diverge as power laws of the control parameter $a$ upon approaching the critical point. The Kadowaki-Woods ratio is shown to...

Topics: Condensed Matter, Strongly Correlated Electrons, Disordered Systems and Neural Networks

Source: http://arxiv.org/abs/1503.04611

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Sep 21, 2013
09/13

by
George Kastrinakis

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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.

Source: http://arxiv.org/abs/0901.0097v2

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Sep 21, 2013
09/13

by
George Kastrinakis

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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...

Source: http://arxiv.org/abs/cond-mat/9609256v1

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Sep 18, 2013
09/13

by
George Kastrinakis

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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.

Source: http://arxiv.org/abs/cond-mat/0110368v2

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Sep 21, 2013
09/13

by
George Kastrinakis

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We introduce a new fermionic variational wavefunction, generalizing the Bardeen-Cooper-Schrieffer (BCS) wavefunction, which is suitable for interacting multi-species spinful systems and sustaining superfluidity. Applications range from quark matter to the high temperature superconductors. A wide class of Hamiltonians, comprising interactions and hybridization of arbitrary momentum dependence between different fermion species, can be treated in a comprehensive manner. This is the case, as both...

Source: http://arxiv.org/abs/0901.2487v13

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Sep 19, 2013
09/13

by
George Kastrinakis

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Based on an unconventional Fermi liquid model, we present several results on the optimally doped and overdoped cuprate superconductors. For the normal state, we provide an analytic demonstration, backed by self-consistent Baym-Kadanoff (BK) numerical calculations, of the linear in $T$ resistivity and linear in 1/$\epsilon$ 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...

Source: http://arxiv.org/abs/cond-mat/9703141v2

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47

Sep 18, 2013
09/13

by
George Kastrinakis

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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....

Source: http://arxiv.org/abs/cond-mat/0502338v2

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49

Sep 22, 2013
09/13

by
George Kastrinakis

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We treat the question of the low temperature behavior of the dephasing rate of the electrons in the presence of elastic spin disorder scattering and interactions. In the frame of a self-consistent diagrammatic treatment, we obtain saturation of the dephasing rate in the limit of low temperature for magnetic scattering, in agreement with the non-interacting case. The magnitude of the dephasing rate is set by the strength of the magnetic scattering rate. We discuss the agreement of our results...

Source: http://arxiv.org/abs/cond-mat/0308300v7