Quantum phases of spin-1 system on 3/4 and 3/5 skewed ladders

TL;DR

This study explores quantum phase transitions in frustrated spin-1 systems on 3/4 and 3/5 skewed ladders, revealing complex ground state behaviors including magnetic, singlet, and symmetry-broken phases.

Contribution

It provides new insights into the ground state phases and transitions of frustrated spin-1 ladders with non-trivial geometries, highlighting the effects of frustration and finite size.

Findings

Ground state switches from singlet to magnetic at J_1 ≥ 1.82 in 3/4 ladder.

Highly frustrated, spiral spin arrangements in 3/5 ladder.

Multiple nonmonotonic ground state transitions as J_1 varies.

Abstract

We study the quantum phase transitions of frustrated antiferromagnetic Heisenberg spin-1 systems on the 3/4 and 3/5 skewed two leg ladder geometries. These systems can be viewed as arising by periodically removing rung bonds from a zigzag ladder. We find that in large systems, the ground state (gs) of the 3/4 ladder switches from a singlet to a magnetic state for $J_1 \ge 1.82$; the gs spin corresponds to ferromagnetic alignment of effective $S = 2$ objects on each unit cell. The gs of antiferromagnetic exchange Heisenberg spin-1 system on a 3/5 skewed ladder is highly frustrated and has spiral spin arrangements. The amplitude of the spin density wave in the 3/5 ladder is significantly larger compared to that in the magnetic state of the 3/4 ladder. The gs of the system switches between singlet state and low spin magnetic states multiple times on tuning $J_1$ in a finite size system. The switching pattern is nonmonotonic as a function of $J_1$, and depends on the system size. It appears to be the consequence of higher $J_1$ favoring higher spin magnetic state and the finite system favoring a standing spin wave. For some specific parameter values, the magnetic gs in the 3/5 system is doubly degenerate in two different mirror symmetry subspaces. This degeneracy leads to spontaneous spin parity and mirror symmetry breaking giving rise to spin current in the gs of the system.