MATERA Juan Mauricio
Phase diagram study of a dimerized spin-S zig?zag ladder
J. M. MATERA; C. A. LAMAS
JOURNAL OF PHYSICS CONDENSED MATTER
IOP PUBLISHING LTD
Lugar: Londres; Año: 2014 vol. 26 p. 326004 - 326004
The phase diagram of a frustrated spin-$S$ zig-zag ladder is studied through different numerical and analytical methods. We show that for arbitrary $S$, there is a family of Hamiltonians for which a fully dimerized state is an exact ground state,being the Majumdar-Ghosh point a particular member of this family.We show that the system presents a transition between a dimerized phase to a N´eel-like phase for $S=1/2$, and spiral phases can appear for large $S$.The phase diagram is characterized by means of a generalization of the usual Mean Field Approximation (MFA). The novelty in the present implementation is to consider the strongest coupled sites as the unit cell. The gap and the excitation spectrum is analyzed through the Random Phase Approximation (RPA). Also, a perturbative treatment to obtain the critical points is discussed. Comparisons of the results with numerical methods like DMRG are also presented.