Partenaires

CNRS
UPS



Rechercher

Sur ce site

Sur le Web du CNRS


Accueil du site > Publications > Publications 2011 > Melting of a frustration-induced dimer crystal and incommensurability in the J1 - J2 two-leg ladder

Melting of a frustration-induced dimer crystal and incommensurability in the J1 - J2 two-leg ladder

A. Lavarelo, G. Roux and N. Laflorencie

par Nicolas Laflorencie - 5 octobre 2011

The phase diagram of an antiferromagnetic ladder with frustrating next-nearest-neighbor couplings along the legs is determined using numerical methods (exact diagonalization and density-matrix renormalization group) supplemented by strong-coupling and mean-field analysis. Interestingly, this model displays remarkable features, bridging the physics of the J1-J2 chain and of the unfrustrated ladder. The phase diagram as a function of the transverse coupling J⊥ and the frustration J2 exhibits an Ising transition between a columnar phase of dimers and the usual rung-singlet phase of two-leg ladders. The transition is driven by resonating valence bond fluctuations in the singlet sector while the triplet spin gap remains finite across the transition. In addition, frustration brings incommensurability in the real-space spin-correlation functions, the onset of which evolves smoothly from the J1-J2 chain value to zero in the large-J⊥ limit. The onset of incommensurability in the spin structure factor and in the dispersion relation is also analyzed. The physics of the frustrated rung-singlet phase is well understood using perturbative expansions and mean-field theories in the large-J⊥ limit. Last, we discuss the effect of the nontrivial magnon dispersion relation on the thermodynamical properties of the system. The relation of this model and its physics to experimental observations on compounds that are currently investigated, such as BiCu2PO6, is eventually addressed.