paper

Thermodynamics of the kagome-lattice Heisenberg antiferromagnet with arbitrary spin

arXiv:1803.06202 · doi:10.1103/PhysRevB.98.024414

Abstract

We use a second-order rotational invariant Green's function method (RGM) and the high-temperature expansion (HTE) to calculate the thermodynamic properties, of the kagome-lattice spin- Heisenberg antiferromagnet with nearest-neighbor exchange . While the HTE yields accurate results down to temperatures of about , the RGM provides data for arbitrary . For the ground state we use the RGM data to analyze the -dependence of the excitation spectrum, the excitation velocity, the uniform susceptibility, the spin-spin correlation functions, the correlation length, and the structure factor. We found that the so-called ordering is more pronounced than the ordering for all values of . In the extreme quantum case the zero-temperature correlation length is only of the order of the nearest-neighbor separation. Then we study the temperature dependence of several physical quantities for spin quantum numbers . As increasing the typical maximum in the specific heat and in the uniform susceptibility are shifted towards lower values of and the height of the maximum is growing. The structure factor exhibits two maxima at magnetic wave vectors corresponding to the and state. We find that the short-range order is more pronounced than the short-range order for all temperatures . For the spin-spin correlation functions, the correlation lengths and the structure factors, we find a finite low-temperature region , , where these quantities are almost independent of .

14 pages, 18 figures

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