158 research outputs found
Universal scaling and quantum critical behavior of CeRhSb(1-x)Sn(x)
We propose a universal scaling rho*chi=const of the electrical resistivity
rho with the inverse magnetic susceptibility chi^(-1) below the temperature of
the quantum-coherence onset for the Ce 4f states in CeRhSb(1-x)Sn(x). In the
regime, where the Kondo gap disappears (x~0.12), the system forms a non-Fermi
liquid (NFL), which transforms into a Fermi liquid at higher temperature. The
NFL behavior is attributed to the presence of a novel quantum critical point
(QCP) at the Kondo insulator - correlated metal boundary. The divergent
behavior of the resistivity, the susceptibility, and the specific heat has been
determined when approaching QCP from the metallic side.Comment: Sent to Phys. Rev. Let
Anderson lattice with explicit Kondo coupling: general features and the field-induced suppression of heavy-fermion state in ferromagnetic phase
We apply the extended (statistically-consistent, SGA) Gutzwiller-type
approach to the periodic Anderson model (PAM) in an applied magnetic field and
in the strong correlation limit. The finite-U corrections are included
systematically by transforming PAM into the form with Kondo-type interaction
and residual hybridization, appearing both at the same time. This effective
Hamiltonian represents the essence of \textit{Anderson-Kondo lattice model}. We
show that in ferromagnetic phases the low-energy single-particle states are
strongly affected by the presence of the applied magnetic field. We also find
that for large values of hybridization strength the system enters the so-called
\textit{locked heavy fermion state}. In this state the chemical potential lies
in the majority-spin hybridization gap and as a consequence, the system
evolution is insensitive to further increase of the applied field. However, for
a sufficiently strong magnetic field, the system transforms from the locked
state to the fully spin-polarized phase. This is accompanied by a metamagnetic
transition, as well as by drastic reduction of the effective mass of
quasiparticles. In particular, we observe a reduction of effective mass
enhancement in the majority-spin subband by as much as 20% in the fully
polarized state. The findings are consistent with experimental results for
CeLaB compounds. The mass enhancement for the spin-minority
electrons may also diminish with the increasing field, unlike for the
quasiparticles states in a single narrow band in the same limit of strong
correlations
Statistical properties and statistical interaction for particles with spin: Hubbard model in one dimension and statistical spin liquid
We derive the statistical distribution functions for the Hubbard chain with
infinite Coulomb repulsion among particles and for the statistical spin liquid
with an arbitrary magnitude of the local interaction in momentum space.
Haldane's statistical interaction is derived from an exact solution for each of
the two models. In the case of the Hubbard chain the charge (holon) and the
spin (spinon) excitations decouple completely and are shown to behave
statistically as fermions and bosons, respectively. In both cases the
statistical interaction must contain several components, a rule for the
particles with the internal symmetry.Comment: (RevTex, 16 pages, improved version
Coexistence of spin-triplet superconductivity with magnetism within a single mechanism for orbitally degenerate correlated electrons: Statistically-consistent Gutzwiller approximation
An orbitally degenerate two-band Hubbard model is analyzed with inclusion of
the Hund's rule induced spin-triplet paired states and their coexistence with
magnetic ordering. The so-called statistically consistent Gutzwiller
approximation (SGA) has been applied to the case of a square lattice. The
superconducting gaps, the magnetic moment, and the free energy are analyzed as
a function of the Hund's rule coupling strength and the band filling. Also, the
influence of the intersite hybridization on the stability of paired phases is
discussed. In order to examine the effect of correlations the results are
compared with those calculated earlier within the Hartree-Fock (HF)
approximation combined with the Bardeen-Cooper-Schrieffer (BCS) approach.
Significant differences between the two used methods (HF+BCS vs. SGA+real-space
pairing) appear in the stability regions of the considered phases. Our results
supplement the analysis of this canonical model used widely in the discussions
of pure magnetic phases with the detailed elaboration of the stability of the
spin-triplet superconducting states and the coexistent magnetic-superconducting
states. At the end, we briefly discuss qualitatively the factors that need to
be included for a detailed quantitative comparison with the corresponding
experimental results
Renormalized mean-field t-J model of high-Tc superconductivity: comparison with experiment
Using an advanced version of the renormalized mean-field theory (RMFT) for
the t-J model, we examine spin-singlet superconducting (SC) state of -symmetry. Overall doping dependence of the SC gap magnitude is in good
agreement with experimental results for (BSCCO) and
(LSCO) compounds at the
optimal doping and in the overdoped regime. We also calculate the dispersion
relation for the Bogoliubov quasiparticles and compare our findings both with
the angle resolved photoemission data for the cuprates, as well as with the
variational Monte Carlo and other mean-field studies. Within the method
proposed by Fukushima [cf. Phys. Rev. B \textbf{78}, 115105 (2008)], we analyze
different forms of the t-J Hamiltonian, i.e. modifications caused by the form
of exchange interaction, and by the presence of three-site terms. It is shown
that although the former has a small influence, the latter suppresses strongly
the superconductivity. We also analyze the temperature dependence of the gap
magnitude and compare the results with those of the recently introduced
finite-temperature renormalized mean-field theory (TRMFT) of Wang et al. [cf.
Phys. Rev. B \textbf{82}, 125105 (2010)].Comment: 7 pages, 6 figures, 2 tables. Submitted to Physical Review
Unconventional superconducting phases in a correlated two-dimensional Fermi gas of nonstandard quasiparticles: a simple model
We discuss a detailed phase diagram and other microscopic characteristics on
the applied magnetic field - temperature (H_a-T) plane for a simple model of
correlated fluid represented by a two-dimensional (2D) gas of heavy
quasiparticles with masses dependent on the spin direction and the effective
field generated by the electron correlations. The consecutive transitions
between the Bardeen-Cooper-Schrieffer (BCS) and the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases are either continuous or
discontinuous, depending on the values of H_a and T. In the latter case, weak
metamagnetic transitions occur at the BCS-FFLO boundary. We single out two
different FFLO phases, as well as a reentrant behaviour of one of them at high
fields. The results are compared with those for ordinary Landau quasiparticles
in order to demonstrate the robustness of the FFLO states against the BCS state
for the case with spin-dependent masses (SDM). We believe that the mechanism of
FFLO stabilization by SDM is generic: other high-field low-temperature (HFLT)
superconducting phases benefit from SDM as well.Comment: 10 pages, 4 figure
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