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arXiv · 1103.1793

Disorder-induced Spin Gap in the Zigzag Spin-1/2 Chain Cuprate Sr_{0.9}Ca_{0.1}CuO_2

F. Hammerath·S. Nishimoto·H. -J. Grafe·A. U. B. Wolter·V. Kataev·P. Ribeiro·C. Hess·S. -L. Drechsler·B. Buechner
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Abstract

We report a comparative study of 63Cu Nuclear Magnetic Resonance spin lattice relaxation rates, T_1^{-1}, on undoped SrCuO_2 and Ca doped Sr_{0.9}Ca_{0.1}CuO_2 spin chain compounds. A temperature independent T_1^{-1} is observed for SrCuO_2 as expected for an S=1/2 Heisenberg chain. Surprisingly, we observe an exponential decrease of T_1^{-1} for T < 90,K in the Ca-doped sample evidencing the opening of a spin gap. The data analysis within the J_1-J_2 Heisenberg model employing density-matrix renormalization group calculations suggests an impurity driven small alternation of the J_2-exchange coupling as a possible cause of the spin gap.

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F. Hammerath, S. Nishimoto, H. -J. Grafe, A. U. B. Wolter, V. Kataev, P. Ribeiro, C. Hess, S. -L. Drechsler, B. Buechner. 2011-06-30. Disorder-induced Spin Gap in the Zigzag Spin-1/2 Chain Cuprate Sr_{0.9}Ca_{0.1}CuO_2. https://doi.org/10.1103/physrevlett.107.017203

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