Effective action of the weakly doped t-J model and spin-wave excitations in the spin-glass phase of La_{2-x}Sr_xCuO_4

TL;DR

This paper develops a new effective field theory for the lightly doped t-J model, revealing a Berry phase term, and predicts complex spin-wave excitations in the spin-glass phase of La_{2-x}Sr_xCuO_4, including distinct in-plane and out-of-plane modes.

Contribution

It introduces a novel low-energy effective field theory with a Berry phase term for the extended t-J model in light doping regimes.

Findings

Predicts two distinct spin-wave excitation branches in the spin-glass phase.

Calculates doping-dependent features of out-of-plane modes.

Provides inelastic neutron scattering intensities for these excitations.

Abstract

We derive the low-energy effective field theory of the extended t-J model in the regime of light doping. The action includes a previously unknown Berry phase term, which is discussed in detail. We use this effective field theory to calculate spin-wave excitations in the disordered spin spiral state of La_{2-x}Sr_xCuO_4 (the spin-glass phase). We predict an excitation spectrum with two distinct branches: The in-plane mode has the usual linear spin-wave dispersion and the out-of-plane mode shows non-trivial doping dependent features. We also calculate the intensities for inelastic neutron scattering in these modes.