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arXiv:1902.04008

Magnon excitations in $Cs_2CuAl_4O_8$ - a bond alternating S=1/2 spin chain with next nearest neighbor coupling

Satyaki Kar

Published Feb 11, 2019• 0 citations
arXivHTMLPDF

Abstract

A recent density functional theory (DFT) based analysis, complemented with Quantum Monte Carlo calculations revealed a highly spin-frustrating nature of the one-dimensional spin-$\frac{1}{2}$ compound $Cs_2CuAl_4O_8$ that comprises of unique bond alternations and relatively strong next nearest neighbor interactions. This article gives a brief account on possible magnon excitations that can appear in the ground state of such systems. We find that the spin waves obtained on top of coplanar helical reference states show multiple magnon modes (both acoustic and optical). However, those magnon modes turn out to be stable only in the absence of bond alternations.

DOI
10.48550/arxiv.1902.04008

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Magnon excitations in Cs2CuAl4O8Cs_2CuAl_4O_8Cs2​CuAl4​O8​ - a bond alternating S=1/2 spin chain with next nearest neighbor coupling
A recent density functional theory (DFT) based analysis, complemented with Quantum Monte Carlo calculations revealed a highly spin-frustrating nature of the one-dimensional spin-12\frac{1}{2}21​ compound Cs2CuAl4O8Cs_2CuAl_4O_8Cs2​CuAl4​O8​ that comprises of unique bond alternations and relatively strong next nearest neighbor interactions. This article gives a brief account on possible magnon excitations that can appear in the ground state of such systems. We find that the spin waves obtained on top of coplanar helical reference states show multiple magnon modes (both acoustic and optical). However, those magnon modes turn out to be stable only in the absence of bond alternations.
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The nature of multimagnon excitations in alternating spin/bond ferromagnetic chains are studied using a combination of scaling methods and the recursion method. Two-magnon excitations for a Heisenberg chain with either alternating spin magnitudes, SSS and ${S}^{\ensuremath{'}},$ or alternating nearest-neighbor couplings, J1{J}_{1}J1​ and J2{J}_{2}J2​ can be studied using real-space rescaling techniques. These results are then used to investigate three-magnon excitations using the recursion method.
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