Incommensurate spin correlations in Heisenberg spin-1/2 zig-zag ladders

TL;DR

This paper develops a low-energy theory for frustrated spin-1/2 ladders, revealing incommensurate correlations and novel ground states, including spin nematic and spiral orders, with applications to neutron scattering experiments.

Contribution

It introduces a new interchain coupling that breaks parity symmetry, leading to incommensurate correlations and novel phases in frustrated spin ladders.

Findings

Discovery of incommensurate correlations in the ground state.

Identification of a spin nematic phase in single ladders.

Prediction of three-dimensional spiral order in coupled chains.

Abstract

We develop a low-energy effective theory for spin-1/2 frustrated two-leg Heisenberg spin ladders. We obtain a new type of interchain coupling that breaks parity symmetry. In the presence of an XXZ-type anisotropy, this interaction gives rise to a novel ground state, characterized by incommensurate correlations. In the case of a single ladder, this state corresponds to a spin nematic phase. For a frustrated quasi-one-dimensional system of infinitely many weakly coupled chains, this state develops true three dimensional spiral order. We apply our theory to recent neutron scattering experiments on $Cs_2CuCl_4$.