arXiv subjects

Marcin M. Wysokinski

Publications and source records attributed to Marcin M. Wysokinski.

4 recordsLinked to original sources

arXiv2017

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

We investigate the unitary dynamics following a sudden increase $ΔU>0$ of repulsion in the paramagnetic sector of the half-filled Hubbard model on a Bethe lattice, by means of a variational approach that combines a Gutzwiller wavefunction with a partial Schrieffer-Wolff transformation, both defined through time-dependent variational parameters. Besides recovering at $ΔU_c$ the known dynamical transition linked to the equilibrium Mott transition, we find pronounced dynamical anomaly at larger $ΔU_*>ΔU_c$ manifested in a singular behaviour of the long-time average of double occupancy. Although the real-time dynamics of the variational parameters at $ΔU_*$ strongly resembles the one at $ΔU_c$, careful frequency spectrum analysis suggests a dynamical crossover, instead of a dynamical transition, separating regions of a different behaviour of the spin-exchange.

cond-mat.str-el↗

arXiv2017

Mott physics beyond Brinkman-Rice scenario

The main flaw of the well-known Brinkman-Rice description, obtained through the Gutzwiller approximation, of the paramagnetic Mott transition in the Hubbard model is in neglecting high-energy virtual processes that generate for instance the antiferromagnetic exchange $J\sim t^2/U$. Here we propose a way to capture those processes by combining the Brinkman-Rice approach with a variational Schrieffer-Wolff transformation, and apply this method to study the single-band metal-to-insulator transition in a Bethe lattice with infinite coordination number, where the Gutzwiller approximation becomes exact. We indeed find for the Mott transition a description very close to the real one provided by dynamical mean-field theory; an encouraging result in view of possible applications to more involved models.

cond-mat.str-el↗

arXiv2016

Many-body breakdown of indirect gap in topological Kondo insulators

We show that the inclusion of nonlocal correlation effects in a variational wave function for the ground state of a topological Anderson lattice Hamiltonian is capable of describing both topologically trivial insulating phases and nontrivial ones characterized by an indirect gap, as well as its closure at the transition into a metallic phase. The method, though applied to an oversimplified model, thus captures the metallic and insulating states that are indeed observed in a variety of Kondo semiconductors, while accounting for topologically nontrivial band structures.

cond-mat.str-el↗

arXiv2014

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.

cond-mat.str-el↗