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arXiv · 1203.2215

Nature of the low energy excitations in the short range ordered region of Cs$_2$CuCl$_4$ as revealed by $^{133}$Cs NMR

M. -A. Vachon·G. Koutroulakis·V. F. Mitrović·Ookie Ma·J . B. Marston·A. P. Reyes·P. Kuhns·R. Coldea·Z. Tylczynski
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Abstract

We report nuclear magnetic resonance measurements of the spin-1/2 anisotropic triangular lattice antiferromagnet Cs$_2$CuCl$_4$ as a function of temperature and applied magnetic field. The observed temperature and magnetic field dependence of the NMR relaxation rate suggests that low energy excitations in the short-range ordered region stabilized over a wide range of intermediate fields and temperatures of the phase diagram are gapless or nearly gapless fermionic excitations. An upper bound on the size of the gap of 0.037 meV $\approx J/10$ is established. The magnetization and NMR relaxation rate can be qualitatively described either by a quasi-1D picture of weakly coupled chains, or by mean-field theories of specific 2D spin liquids; however, quantitative differences exist between data and theory in both cases. This comparison indicates that 2D interactions are quantitatively important in describing the low-energy physics.

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M. -A. Vachon, G. Koutroulakis, V. F. Mitrović, Ookie Ma, J . B. Marston, A. P. Reyes, P. Kuhns, R. Coldea, Z. Tylczynski. 2012-03-10. Nature of the low energy excitations in the short range ordered region of Cs$_2$CuCl$_4$ as revealed by $^{133}$Cs NMR. https://doi.org/10.1088/1367-2630%2F13%2F9%2F093029

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