Quantum dimer phases in a frustrated spin ladder: Effective field theory approach and exact diagonalization

TL;DR

This paper investigates the phase diagram of a frustrated spin ladder using effective field theory and exact diagonalization, revealing two new dimerized phases and characterizing phase transitions.

Contribution

It introduces a combined approach of effective field theory and exact diagonalization to identify new quantum phases in a frustrated spin ladder.

Findings

Discovery of two new dimerized phases

Identification of phase transition types (first order and Ising universality)

Analysis of elementary excitations

Abstract

The phase diagram of a frustrated S=1/2 antiferromagnetic spin ladder with additional next-nearest neighbor exchanges, both diagonal and inchain, is studied by a weak-coupling effective field theory approach combined with exact diagonalization for finite systems. In addition to two known phases with rung-singlet and Haldane-type ground states, we observe two new phases with dimerization along the chains. Furthermore, the transitions between the different phases are studied and shown to be either first order or to belong to the universality class of the two-dimensional Ising model. The nature of elementary excitations is discussed briefly.