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Extended quantum critical phase in a magnetized spin-1/2 antiferromagnetic chain

M. B. Stone·D. H. Reich·C. Broholm·K. Lefmann·C. Rischel·C. P. Landee·M. M. Turnbull
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Abstract

Measurements are reported of the magnetic field dependence of excitations in the quantum critical state of the spin S=1/2 linear chain Heisenberg antiferromagnet copper pyrazine dinitrate (CuPzN). The complete spectrum was measured at k_B T/J <= 0.025 for H=0 and H=8.7 Tesla where the system is ~30% magnetized. At H=0, the results are in quantitative agreement with exact calculations of the dynamic spin correlation function for a two-spinon continuum. At high magnetic field, there are multiple overlapping continua with incommensurate soft modes. The boundaries of these continua confirm long-standing predictions, and the intensities are consistent with exact diagonalization and Bethe Ansatz calculations.

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M. B. Stone, D. H. Reich, C. Broholm, K. Lefmann, C. Rischel, C. P. Landee, M. M. Turnbull. 2003-03-18. Extended quantum critical phase in a magnetized spin-1/2 antiferromagnetic chain. https://doi.org/10.1103/physrevlett.91.037205

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