Universal behavior of spin-mediated energy transport in S=1/2 chain cuprates: BaCu2Si2O7 as an example

The thermal conductivity of the spin-1/2 chain cuprate BaCu2Si2O7 was measured along different crystallographic directions in the temperature region between 0.5 and 300 K. The thermal conductivity along the chain direction considerably exceeds that along perpendicular directions. Near the antiferromagnetic transition at T_N = 9.2 K the data indicates enhanced scattering of phonons by critical fluctuations in the spin system. A comparison of the data above T_N with available results on similar materials reveals similarities in the main features of the temperature dependence of the mean free path of itinerant spin excitations. This universal behavior is most likely caused by the spin-lattice interaction.