Eur. Phys. J. B (2014) 87: 226
https://doi.org/10.1140/epjb/e2014-50423-7

Regular Article

Phase diagram of the alternating-spin Heisenberg chain with extra isotropic three-body exchange interactions

¹ Department of Physics, Bielefeld University, P.O. Box 100131, 33501 Bielefeld, Germany
² Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko chaussee 72, 1784 Sofia, Bulgaria

^a e-mail: jschnack@uni-bielefeld.de

Received: 23 June 2014
Received in final form: 13 August 2014
Published online: 7 October 2014

Abstract

For the time being isotropic three-body exchange interactions are scarcely explored and mostly used as a tool for constructing various exactly solvable one-dimensional models, although, generally speaking, such competing terms in generic Heisenberg spin systems can be expected to support specific quantum effects and phases. The Heisenberg chain constructed from alternating S = 1 and σ = 1/2 site spins defines a realistic prototype model admitting extra three-body exchange terms. Based on numerical density-matrix renormalization group (DMRG) and exact diagonalization (ED) calculations, we demonstrate that the additional isotropic three-body terms stabilize a variety of partially-polarized states as well as two specific non-magnetic states including a critical spin-liquid phase controlled by two Gaussinal conformal theories as well as a critical nematic-like phase characterized by dominant quadrupolar S-spin fluctuations. Most of the established effects are related to some specific features of the three-body interaction such as the promotion of local collinear spin configurations and the enhanced tendency towards nearest-neighbor clustering of the spins. It may be expected that most of the predicted effects of the isotropic three-body interaction persist in higher space dimensions.