We have developed a new, efficient numerical method for solving one and two holes in the antiferromagnetic background. We have explored the influence of two different polarizations of quantum oxygen vibrations on the spacial symmetry of the bound magnetic bipolaron in the context of the t-J model. Electron phonon coupling to transverse polarization stabilizes the bound bipolar state with the d-wave symmetry. The existence of a magnetic background is essential for the formation of a d-wave bipolaron state.

COBISS.SI-ID: 2189924

The memory-function approach to spin dynamics in doped antiferromagnetic insulator combined with the assumption of temperature-independent static spin correlations and constant collective-mode damping leads to ?/T scaling in a broad range. The theory involving a nonuniversal scaling parameter is used to analyze recent inelastic neutron-scattering results for underdoped cuprates. Adopting modified damping function also the emerging central peak in low-doped cuprates at low temperatures can be explained within the same framework.

COBISS.SI-ID: 22562343

We developed a model of birelaxors, i.e., materials that exhibit simultaneously the properties of relaxor ferroelectrics and relaxors ferromagnets. We estimated the magnetic field at which the relaxation of the dielectric polarization is fully suppressed at room temperature. This is a new phenomenon recently discovered at University of Puerto Rico.

COBISS.SI-ID: 22709287

Entanglement of spins is analyzed for two electrons extracted from a mixed many electron state by projecting onto the two-electron subspace. As an example, the thermal entanglement for a qubit pair with an anisotropic Heisenberg and the Dzyaloshinskii-Moriya interactions in an inhomogeneous magnetic field is given analytically. Remarkably, the concurrence of a pair of electrons with antiparallel spins and in a delocalised orbital state is given by the scalar product of the state with its spin-flipped state and not with the time-reversed state.

COBISS.SI-ID: 22644775

Time dependent DMRG method with matrix product ansatz has been employed for explicit computation of non-equilibrium steady state density operators of several integrable and non-integrable quantum chains, which are driven far from equlibrium by means of Markovian couplings to external baths at the two ends. Quantum chains of sizes up to 100 spins/qubits can easily be simulated. Our results are demonstrated by performing explicit simulations of steady states and calculations of energy/spin densities/currents in several problems of heat and spin transport in quantum spin chains.

COBISS.SI-ID: 2150756