440 research outputs found
Properties of an almost localized Fermi liquid in applied magnetic field revisited: Statistically consistent Gutzwiller approach
We discuss the Hubbard model in an applied magnetic field and analyze the
properties of neutral spin-1/2 fermions within the so-called statistically
consistent Gutzwiller approximation (SGA). The magnetization curve reproduces
in a semiquantitative manner the experimental data for liquid 3 He in the
regime of moderate correlations and in the presence of small number of vacant
cells, modeled by a non-half filled-band situation, when a small number of
vacancies (up to 5%) is introduced in the virtual fcc lattice. We also present
the results for the magnetic susceptibility and the specific heat, in which a
metamagnetic-like behavior is also singled out in a non-half-filled band case
Holographic superconductivity in the presence of dark matter: basic issues
The holographic approach to study strongly coupled superconductors in the
presence of dark matter is reviewed. We discuss the influence of dark matter on
the superconducting transition temperature of both s-wave and p-wave
holographic superconductors. The upper critical field, coherence length,
penetration depth of holographic superconductors as well as the metal-insulator
transitions have also been analysed. Issues related to the validity of AdS/CFT
correspondence for the description of superconductors studied in the laboratory
and possible experiments directed towards the detection of dark matter are
discussed. In doing so we shall compare our assumptions and assertions with
those generally accepted in the elementary particle experiments aimed at the
detection of dark matter particles.Comment: 5+ pages, 1 figure, National Conference on Superconductivity 2015,
Karpacz, Polan
Holographic vortices in the presence of dark matter sector
The {\it dark matter} seem to be an inevitable ingredient of the total matter
configuration in the Universe and the knowledge how the {\it dark matter}
affects the properties of superconductors is of vital importance for the
experiments aimed at its direct detection. The homogeneous magnetic field
acting perpendicularly to the surface of (2+1) dimensional s-wave holographic
superconductor in the theory with {\it dark matter} sector has been modeled by
the additional -gauge field representing dark matter and coupled to the
Maxwell one. As expected the free energy for the vortex configuration turns out
to be negative. Importantly its value is lower in the presence of {\it dark
matter} sector. This feature can explain why in the Early Universe first the
web of {\it dark matter} appeared and next on these gratings the ordinary
matter forming cluster of galaxies has formed.Comment: 23 pages, JHEP-styl
Magnetotransport of Weyl semimetals with topological charge and chiral anomaly
We calculate the magnetoconductivity of the Weyl semimetal with
symmetry and chiral anomaly utilizing the recently developed
hydrodynamic theory. The system in question will be influenced by magnetic
fields connected with ordinary Maxwell and the second -gauge field, which
is responsible for anomalous topological charge. The presence of chiral anomaly
and anomalous charge endow the system with new transport
coefficients. We start with the linear perturbations of the hydrodynamic
equations and calculate the magnetoconductivity of this system. The holographic
approach in the probe limit is implemented to obtain the explicit dependence of
the longitudinal magnetoconductivities on the magnetic fields.Comment: 35 pages, 4 figures, LaTex, the title was changed, the version meets
the printed one
P-wave holographic superconductor/insulator phase transitions affected by dark matter sector
The holographic approach to building the p-wave superconductors results in
three different models: the Maxwell-vector, the SU(2) Yang-Mills and the
helical. In the probe limit approximation, we analytically examine the
properties of the first two models in the theory with {\it dark matter} sector.
It turns out that the effect of {\it dark matter} on the Maxwell-vector p-wave
model is the same as on the s-wave superconductor studied earlier. For the
non-Abelian model we study the phase transitions between p-wave holographic
insulator/superconductor and metal/superconductor.
Studies of marginally stable modes in the theory under consideration allow us
to determine features of p-wave holographic droplet in a constant magnetic
field. The dependence of the superconducting transition temperature on the
coupling constant to the {\it dark matter} sector is affected by the
{\it dark matter} density . For the transition
temperature is a decreasing function of . The critical chemical
potential for the quantum phase transition between insulator and metal
depends on the chemical potential of dark matter and for is a
decreasing function of .Comment: 25 pages, 3 figures, JHEP style (included), version accepted for
publication in JHE
Holographic calcualtion of the magneto-transport coefficients in Dirac semimetals
Based on the gauge/gravity correspondence we have calculated the
thermoelectric kinetic and transport characteristics of the strongly
interacting materials in the presence of perpendicular magnetic field. The 3+1
dimensional system with Dirac-like spectrum is considered as a strongly
interacting one if it is close to the particle-hole symmetry point. Transport
in such system has been modeled by the two interacting vector fields. In the
holographic theory the momentum relaxation is caused by axion field and leads
to finite values of the direct current transport coefficients. We have
calculated conductivity tensor in the presence of mutually perpendicular
electric and magnetic fields and temperature gradient. The geometry differs
from that in which magnetic field lies in the same plane as an electric one and
temperature gradient.Comment: 26 pages, 7 figure
Gutzwiller Wave-Function Solution for Anderson Lattice Model: Emerging Universal Regimes of Heavy Quasiparticle States
The recently proposed diagrammatic expansion (DE) technique for the full
Gutzwiller wave function (GWF) is applied to the Anderson lattice model (ALM).
This approach allows for a systematic evaluation of the expectation values with
GWF in the finite dimensional systems. It introduces results extending in an
essential manner those obtained by means of standard Gutzwiller Approximation
(GA) scheme which is variationally exact only in infinite dimensions. Within
the DE-GWF approach we discuss principal paramagnetic properties of ALM and
their relevance to heavy fermion systems. We demonstrate the formation of an
effective, narrow -band originating from atomic -electron states and
subsequently interpret this behavior as a mutual intersite -electron
coherence; a combined effect of both the hybridization and the Coulomb
repulsion. Such feature is absent on the level of GA which is equivalent to the
zeroth order of our expansion. Formation of the hybridization- and
electron-concentration-dependent narrow effective -band rationalizes common
assumption of such dispersion of levels in the phenomenological modeling of
the band structure of CeCoIn. Moreover, we show that the emerging
-electron coherence leads in a natural manner to three physically distinct
regimes within a single model, that are frequently discussed for 4- or 5-
electron compounds as separate model situations. We identify these regimes as:
(i) mixed-valence regime, (ii) Kondo-insulator border regime, and (iii)
Kondo-lattice limit when the -electron occupancy is very close to the
electrons half-filling, . The non-Landau
features of emerging correlated quantum liquid state are stressed.Comment: Submitted to Phys. Rev.
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