Phase diagram of a frustrated asymmetric ferromagnetic spin ladder

TL;DR

This study explores the complex phase diagram of an asymmetric ferromagnetic spin ladder with frustration, revealing new magnetic states and phase transitions using advanced numerical methods.

Contribution

It introduces the phase diagram of an asymmetric ferromagnetic spin ladder with frustration, identifying novel magnetic states and phase transitions.

Findings

Discovery of a magnetic canted state in strongly asymmetric ladders.

Identification of a spin-stripe state at intermediate asymmetry.

Observation of a first-order transition from FM to spin-stripe state.

Abstract

We perform a systematic investigation on the ground state of an asymmetric two-leg spin ladder (where exchange couplings of the legs are unequal) with ferromagnetic (FM) nearest-neighbor interaction and diagonal anti-ferromagnetic frustration using the Density Matrix Renormalization Group (DMRG) method. When the ladder is strongly asymmetric with moderate frustration, a magnetic canted state is observed between a FM state and a singlet dimerized state. The phase boundaries are dependent on the asymmetric strength $\alpha_{a}$. On the other hand, when the asymmetric strength is intermediate, a so-called spin-stripe state (spins align parallel on same legs, but antiparallel on rungs) is discovered, and the system experiences a first-order phase transition from the FM state to the spin-stripe state upon increasing frustration. We present numerical evidence to interpret the phase diagram in terms of frustration and the asymmetric strength.