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

¹ Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine - Svientsitskii Street 1, 79011 L'viv, Ukraine
² Department for Theoretical Physics, Ivan Franko National University of L'viv - Drahomanov Street 12, 79005 L'viv, Ukraine
³ Abdus Salam International Centre for Theoretical Physics - Strada Costiera 11, 34151 Trieste, Italy
⁴ Department of Theoretical Physics and Astrophysics, Faculty of Science, P. J. Šafárik University Park Angelinum 9, 040 01 Košice, Slovak Republic

Received: 8 October 2015
Accepted: 4 November 2015

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 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.