Effective low-energy description of almost Ising-Heisenberg diamond chain

TL;DR

This paper derives an effective low-energy Hamiltonian for a frustrated spin-1/2 Ising-Heisenberg diamond chain with added XY interactions, revealing a new spin-liquid phase absent in the original model.

Contribution

The authors develop a perturbative method to simplify the quantum model and uncover a novel spin-liquid phase in the modified system.

Findings

Effective Hamiltonian free of frustration

Emergence of a spin-liquid phase with variable magnetization

Method applicable to other hybrid Ising-Heisenberg systems

Abstract

We consider a geometrically frustrated spin-1/2 Ising-Heisenberg diamond chain, which is an exactly solvable model when assuming part of the exchange interactions as Heisenberg ones and another part as Ising ones. A small $XY$ part is afterwards perturbatively added to the Ising couplings, which enabled us to derive an effective Hamiltonian describing the low-energy behavior of the modified but full quantum version of the initial model. The effective model is much simpler and free of frustration. It is shown that the $XY$ part added to the originally Ising interaction gives rise to the spin-liquid phase with continuously varying magnetization, which emerges in between the magnetization plateaus and is totally absent in the initial hybrid diamond-chain model. The elaborated approach can also be applied to other hybrid Ising-Heisenberg spin systems.