arXiv subjects

V. Turkowski

Publications and source records attributed to V. Turkowski.

22 records · Page 2Linked to original sources

arXiv2003

Superconducting properties of the 2D models with different types of inter-particle coupling

The superconducting properties of the 2D fermion system with local and different types of the indirect boson-exchange attractions in the cases of s-wave and d-wave pairing are reviewed and analysed at T=0. In particular, the possibility of the crossover from the Bose-Einstein condensation regime to the BCS-like superconductivity with the carrier density and coupling changing in the case of different pairing channels is discussed. Gaussian fluctuations of the order parameter are taken into account and the carrier density dependence of the gap is studied in this case. The role of the interaction form in the physical behavior of the systems is also discussed.

cond-mat.supr-con↗

arXiv2003

Temperature-doping phase diagram of layered superconductors

The superconducting properties of a layered system are analyzed for the cases of zero- and non-zero angular momentum of the pairs. The effective thermodynamic potential for the quasi-2D XY-model for the gradients of the phase of the order parameter is derived from the microscopic superconducting Hamiltonian. The dependence of the superconducting critical temperature T_c on doping, or carrier density, is studied at different values of coupling and inter-layer hopping. It is shown that the critical temperature T_c of the layered system can be lower than the critical temperature of the two-dimensional Berezinskii-Kosterlitz-Thouless transition T_BKT at some values of the model parameters, contrary to the case when the parameters of the XY-model do not depend on the microscopic Hamiltonian parameters.

cond-mat.supr-con↗

arXiv2003

Non-equilibrium properties of the S=1/2 Heisenberg model in a time-dependent magnetic field

The time-dependent behavior of the Heisenberg model in contact with a phonon heat bath and in an external time-dependent magnetic field is studied by means of a path integral approach. The action of the phonon heat bath is taken into account up to the second order in the coupling to the heath bath. It is shown that there is a minimal value of the magnetic field below which the average magnetization of the system does not relax to equilibrium when the external magnetic field is flipped. This result is in qualitative agreement with the mean field results obtained within $ϕ^{4}$-theory.

cond-mat.stat-mech↗

arXiv2002

Crossover from superfluidity to superconductivity in a system with doping dependent attraction

Zero temperature crossover from superfluidity to superconductivity with carrier density increasing is studied for a two-dimensional system in the s-wave and d-wave pairing channels. It was assumed that the particle attraction correlation length depends on carrier density $n_f$ as $r_0\sim1/\sqrt{n_f}$. Such a dependence was found experimentally for the radius of magnetic correlations in $La_{2-x}Sr_xCuO_4$. The short range Coulomb repulsion was also taken into account. It is shown that the behaviour of the system with doping is fundamentally different from the case with $r_0(n_f)=const$. In particular, similarly to the d-wave case, the crossover in the s-channel takes place only if the coupling is larger of some minimal value, otherwise the Cooper pairing scenario takes place at any small carrier density. The relevance of the model to high-temperature superconductors is discussed.

cond-mat.supr-con↗