Eur. Phys. J. B (2017) 90: 105
https://doi.org/10.1140/epjb/e2017-70716-5

Regular Article

Phase diagram of the frustrated asymmetric ferromagnetic spin ladder

¹ School of Physics Science and Technology, Yangzhou University, Yangzhou 225002, P.R. China
² Department of Physics, The University of Texas, Austin, TX 78712, USA

^a e-mail: yjliu@yzu.edu.cn

Received: 6 December 2016
Received in final form: 27 February 2017
Published online: 5 June 2017

Abstract

We present 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 method. When the ladder is strongly asymmetric with moderate frustration, a magnetic canted state is observed between an FM state and a singlet dimerized state. The phase boundaries are dependent on the asymmetric strength. On the other hand, when the asymmetric strength is intermediate, a so-called spin-stripe state (spins align parallel on the 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. Numerical evidence is presented for interpretation of the phase diagram in terms of frustration and the asymmetric strength.