arXiv:1602.05383 · Physical Review B
Quantum rotors on the AB2 chain with competing interactions
Antônio Sandoildo Freitas Tenório, R. R. Montenegro-Filho, Mauricio D. Coutinho-Filho
Abstract
We present the ground-state phase diagram of $q=1/2$ quantum-rotor chains with competing interactions (frustration) calculated through cluster variational mean field approaches. We consider two interaction patterns, named ${\text{F}}_{1}$ and ${\text{F}}_{2}$ models, between the quantum-rotor momentum and position operators, which follow exchange patterns of known one-dimensional spin-1/2 systems with a ferrimagnetic state in their phase diagrams. The spin-1/2 ${\text{F}}_{1}$ model is known as the diamond chain and is related to the azurite compound, while the spin-1/2 ${\text{F}}_{2}$ model was recently shown to present a frustration-induced condensation of magnons. We provide a detailed comparison between the quantum-rotor phase diagrams, in single- and multisite mean-field approaches, and known results for the spin-1/2 models, including exact diagonalization and density matrix renormalization group data for these systems, as well as phase diagrams of the associated classical models.