Thermal conductivity due to spinons in the one-dimensional quantum spin system Sr₂V₃O₉

We have measured the thermal conductivity along different directions of the S = 1/2 one-dimensional spin system Sr₂V₃O₉ in magnetic fields up to 14 T. It has been found that the thermal conductivity along the [101] direction, κ_[101], is large and markedly suppressed by the application of magnetic field, indicating that there is a large contribution of spinons to κ_[101] and that the spin chains run along the [101] direction. The maximum value of the thermal conductivity due to spinons is ∼14W/(K·m) along the [101] direction, supporting the empirical law that the magnitude of the thermal conductivity due to spinons is roughly proportional to the antiferromagnetic interaction between the nearest neighboring spins.