Ground-state phase diagram of the frustrated spin-1/2 two-leg honeycomb ladder (A5)

Qiang Luo, Shijie Hu, Jize Zhao, Alexandros Metavitsiadis, Sebastian Eggert, and Xiaoqun Wang:

Phys. Rev. B, 97, 214433 (2018)

🔓 arXiv:1804.00008 (2018)

We investigate a spin-1/2 two-leg honeycomb ladder with frustrating next-nearest-neighbor (NNN) coupling along the legs, which is equivalent to two J1−J2 spin chains coupled with J⊥ at odd rungs. The full parameter region of the model is systematically studied using conventional and infinite density-matrix renormalization group as well as bosonization. The rich phase diagram consists of five distinct phases: a Haldane phase, a NNN-Haldane phase, and a staggered dimer phase when J⊥<0; a rung singlet phase and a columnar dimer phase when J⊥>0. An interesting reentrant behavior from the dimerized phase into the Haldane phase is found as the frustration J2 increases. The universalities of the critical phase transitions are fully analyzed. Phase transitions between dimerized and disordered phases belong to the two-dimensional Ising class with a central charge c=1/2. The transition from the Haldane phase to NNN-Haldane phase is of a weak topological first order, while the continuous transition between the Haldane phase and rung singlet phase has a central charge c=2.