arXiv:cond-mat/0609022

New polarization effect and collective excitation in S=1/2 quasi 1D antiferromagnetic quantum spin chain

S. V. Demishev, A. V. Semeno, Hitoshi Ohta, S. Okubo, I. E. Tarasenko, Ishchenko, T. V., Nikolay E. Sluchanko

Published Sep 1, 2006• 0 citations

Abstract

Anomalous polarization characteristics of magnetic resonance in CuGeO3 doped with 2% of Co impurity are reported. For the Faraday geometry this mode is damped for the microwave field Bw aligned along a certain crystallographic direction showing that the character of magnetic oscillation differs from the standard spin precession. The observed resonance coexists with the ESR on Cu2+ chains and argued not to be caused by "impurity" EPR, as previously claimed, but to correspond to a previously unknown collective mode of magnetic oscillations in S=1/2 AF quantum spin chain.

DOI: 10.48550/arxiv.cond-mat/0609022

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arXiv:cond-mat/0609022

New polarization effect and collective excitation in S=1/2 quasi 1D antiferromagnetic quantum spin chain

S. V. Demishev, A. V. Semeno, Hitoshi Ohta, S. Okubo, I. E. Tarasenko, Ishchenko, T. V., Nikolay E. Sluchanko

Published Sep 1, 2006• 0 citations

arXiv HTML PDF

Abstract

DOI: 10.48550/arxiv.cond-mat/0609022

Related papers

New polarization effect and collective excitation in S = 1/2 quasi-one-dimensional antiferromagnetic quantum spin chain

S. V. Demishev, A. V. Semeno, Hitoshi Ohta +4 more

Anomalous polarization characteristics of magnetic resonance in CuGeO3 doped with 2% Co impurity are reported. For the Faraday geometry, this mode is damped for the microwave field B ω aligned along a certain crystallographic direction, showing that the character of magnetic oscillation differs from the standard spin precession. The observed resonance coexists with the ESR on Cu2+ chains; it is argued not to be caused by “impurity” EPR, as previously claimed, but to correspond to a previously unknown collective mode of magnetic oscillations in an S = 1/2 AF quantum spin chain.Anomalous polarization characteristics of magnetic resonance in CuGeO3 doped with 2% Co impurity are reported. For the Faraday geometry, this mode is damped for the microwave field B ω aligned along a certain crystallographic direction, showing that the character of magnetic oscillation differs from the standard spin precession. The observed resonance coexists with the ESR on Cu2+ chains; it is argued not to be caused by “impurity” EPR, as previously claimed, but to correspond to a previously unknown collective mode of magnetic oscillations in an S = 1/2 AF quantum spin chain.

Journal of Experimental and Theoretical Physics LettersNov 1, 20062 citations

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We discuss the universal theory of localized impurities in the paramagnetic state of 2D antiferromagnets where the spin gap is assumed to be significantly smaller than a typical exchange energy. We study the impurity spin susceptibility near the host quantum transition from a gapped paramagnet to a Néel state, and we compute the impurity-induced damping of the spin-1 mode of the gapped antiferromagnet. Under suitable conditions our results apply also to d-wave superconductors. Doped antiferromagnets (AF) have been the subject of intense studies in the context of the cuprate high-temperature superconductors and other layered transition metal compounds. We present a quantum theory of a particular class of doped AF where it is possible to neglect the coupling between the spin and charge degrees of freedom and consider a theory of the spin excitations alone. Such a theory will apply to (i) quasi-2D ‘spin gap ’ insulators like SrCu2O3 or NaV2O5 inWe discuss the universal theory of localized impurities in the paramagnetic state of 2D antiferromagnets where the spin gap is assumed to be significantly smaller than a typical exchange energy. We study the impurity spin susceptibility near the host quantum transition from a gapped paramagnet to a Néel state, and we compute the impurity-induced damping of the spin-1 mode of the gapped antiferromagnet. Under suitable conditions our results apply also to d-wave superconductors. Doped antiferromagnets (AF) have been the subject of intense studies in the context of the cuprate high-temperature superconductors and other layered transition metal compounds. We present a quantum theory of a particular class of doped AF where it is possible to neglect the coupling between the spin and charge degrees of freedom and consider a theory of the spin excitations alone. Such a theory will apply to (i) quasi-2D ‘spin gap ’ insulators like SrCu2O3 or NaV2O5 in

Jan 1, 20000 citations

k

,--

k

) pairs of quasiparticles at the longitudinal polarization. This kind of absorption of microwaves occurs both in the ordered and specific spin-liquid phases, revealing the presence of quasiparticles in the specific spin-liquid phase.

We report on an electron spin resonance (ESR) study of a nearly one-dimensional (1D) spin-

\frac{1}{2}

chain antiferromagnet,

{\mathrm{Sr}}_{2}{\mathrm{CuO}}_{3}

, with extremely weak magnetic ordering. The ESR spectra at

T>{T}_{N}

, in the disordered Luttinger-spin-liquid phase, reveal nearly ideal Heisenberg-chain behavior with only a very small, field-independent linewidth, $\ensuremath{\sim}1/T$. In the ordered state, below

{T}_{N}

, we identify field-dependent antiferromagnetic resonance modes, which are well described by pseudo-Goldstone magnons in the model of a collinear biaxial antiferromagnet. Additionally, we observe a major resonant mode with unusual and strongly anisotropic properties, which is not anticipated by the conventional theory of Goldstone spin waves. We propose that this unexpected magnetic excitation can be attributed to a field-independent magnon mode renormalized due to its interaction with the high-energy amplitude (Higgs) mode in the regime of weak spontaneous symmetry breaking.