Vladyslav O Cheranovskii
V.N. Karazin Kharkiv National University, Ukraine
Title: Peculiarities of the energy spectrum and the magnetic properties of strongly correlated electron systems on bipartite lattices formed by weakly interacting linear segments
Biography
Biography: Vladyslav O Cheranovskii
Abstract
It is known that the intermediate plateau in field dependence of magnetization is informative characteristic for molecular ferrimagnets and some frustrated spin systems. We demonstrate the existence of intermediate magnetization plateau for a family of one-dimensional bipartite (non-frustrated) spin systems formed by weakly interacting segments and having singlet ground state. In the limit of weak interactions between segments these systems have a similar structure of the lowest part of the energy spectra and we presented simple description for above magnetization plateaus by means of perturbation theory. The increase of the interactions between segments leads to significant modification in the energy spectra and the magnetization curves for our systems. We studied this process numerically by the density matrix renormalization (DMRG) and Quantum Monte-Carlo (QMC) methods. We also performed numerical studies of the spin-Peierls instability for our systems and estimated the corresponding critical exponents for the ground state energy. We studied magnetic properties of the electron systems on finite 2-leg ladder rings formed by weakly interacting rungs and described by infinite-repulsion Hubbard model. For the numerical and analytical study of the lowest energy states of the above systems, we used cyclic spin permutation formalism. We found the possibility of jump-wise change of the ground state spin with the increase of the interaction between rungs. To explain this finite size effect, we derive new modification of magnetic polaron approximation, which agrees well with the results of the exact diagonalization study.