Marcin M. Wysokiński

Ferromagnetism in UGe2: A microscopic model

We provide the microscopic description of magnetic properties of UGe2 and in particular, of its both classical and quantum critical behavior. Namely, we account for all the critical points: the critical ending point (CEP) at the metamagnetic phase transition, the tricritical point (TCP), and the quantum critical end point (QCEP) at the ferromagnetic to paramagnetic phase transition. Their position agrees quantitatively with experiment. Additionally, we predict that the metamagnetic CEP can be traced down to zero temperature and becomes quantum critical point (QCP) by a small decrease of both the total electron concentration and the external pressure. The system properties are then determined by the quantum critical fluctuations appearing near the instability point of the Fermi surface (FS) topology.Anderson lattice model is used to rationalize the principal features of the heavy fermion compound UGe2 by means of the generalized Gutzwiller approach (the SGA method). This microscopic approach successfully reproduces magnetic and electronic properties of this material, in a qualitative agreement with experimental findings from the magnetization measurements, the neutron scattering, and the de Haas-van Alphen oscillations. Most importantly, it explains the appearance, sequence, character, and evolution in an applied magnetic field of the observed in UGe2 ferro- and, para-magnetic phases as an effect of a competition between the f-f electrons Coulomb interaction energy and f-conduction electrons kinetic energy (hybridization)

Properties of an almost localized Fermi liquid in an applied magnetic field revisited: a statistically consistent Gutzwiller approach

We discuss the Hubbard model in an applied magnetic field and analyze the properties of neutral spin-[Formula: see text] fermions within the so-called statistically consistent Gutzwiller approximation. 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 a small number of vacant cells, modeled by a non-half-filled band situation, when a small number of vacancies (∼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.

Seebeck effect in the graphene-superconductor junction

Thermopower of graphene-superconductor (GS) junction is analyzed within the extended Blonder-Tinkham-Klapwijk formalism. Within this approach, we have also calculated the temperature dependence of the zero-bias conductance for GS junction. Both quantities reflect quasi-relativistic nature of massless Dirac fermions in graphene. Both the linear and the non-linear regimes are considered.

Correlation-driven d -wave superconductivity in Anderson lattice model: Two gaps

We present the full Gutzwiller-wave-function solution of the Anderson lattice model in two dimensions that leads to the correlation-driven multigap superconducting (SC) ground state with the dominant

Tricritical wings in UGe2: A microscopic interpretation

d_{x^2-y^2}

Gutzwiller wave-function solution for Anderson lattice model: Emerging universal regimes of heavy quasiparticle states

-wave symmetry. The results are consistent with the principal properties of the heavy-fermion superconductor CeCoIn

Magnetic and thermodynamic properties of correlated fermions - application to liquid 3He

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Interplay of charge and spin dynamics after an interaction quench in the Hubbard model

. We regard the pairing mechanism as universal and thus applicable to other Ce-based heavy-fermion compounds. Additionally, a gain in kinetic energy in the SC state takes place, as is also the case for high-temperature superconductors.

Mott physics beyond the Brinkman-Rice scenario

Abstract In the present work we analyze the second order transition line that connects the tricritical point and the quantum critical ending point on the temperature–magnetic-field plane in UGe2. For the microscopic modeling we employ the Anderson lattice model recently shown to provide a fairly complete description of the full magnetic phase diagram of UGe2 including all the criticalities. The shape of the so-called tricritical wings, i.e. surfaces of the first-order transitions, previously reported by us to quantitatively agree with the experimental data, is investigated here with respect to the change of the total filling and the Lande factor for f electrons which can differ from the free electron value. The analysis of the total filling dependence demonstrates sensitivity of our prediction when the respective positions of the critical ending point at the metamagnetic transition and tricritical point are mismatched as compared to the experiment.

Microscopic mechanism for the unusual antiferromagnetic order and the pressure-induced transition to ferromagnetism in USb2

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