Scalar chiral ground states of spin ladders with four-spin exchanges

TL;DR

This paper demonstrates that four-spin exchanges can induce scalar chiral order in two-leg spin ladders, revealing exact ground states with symmetry breaking and analyzing phase boundaries using duality and matrix-product states.

Contribution

It introduces a novel mechanism for scalar chiral order in spin ladders via four-spin exchanges and identifies exact ground states using duality and matrix-product ansatz.

Findings

Scalar chiral order can be induced by four-spin exchanges.

Exact ground states with scalar chiral order are found.

The SU(4)-symmetric model is at a multicritical point.

Abstract

We show that scalar chiral order can be induced by four-spin exchanges in the two-leg spin ladder, using the spin-chirality duality transformation and matrix-product ansatz. Scalar-chiral-ordered states are found to be exact ground states in a family of spin ladder models. In this scalar chiral phase, there is a finite energy gap above the doubly degenerate ground states and a $Z_2 \times Z_2 \times Z_2$ symmetry is fully broken. It is also shown that the SU(4)-symmetric model, which is self-dual under the duality transformation, is on a multicritical point surrounded by the staggered dimer phase, the staggered scalar chiral phase, and the gapless phase.