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We study the magnetic field-dependence of the thermal conductivity due tomagnetic excitations in frustrated spin-1/2 Heisenberg chains. Near thesaturation field, the system is described by a dilute gas of weakly-interactingfermions (free-fermion fixed point). We show that in this regime the thermalconductivity exhibits a non-monotonic behavior as a function of the ratio$\alpha= J_2/J_1$ between second and first nearest-neighbor antiferromagneticexchange interactions. This result is a direct consequence of the splitting ofthe single-particle dispersion minimum into two minima that takes place at theLifshitz point $\alpha=1/4$. Upon increasing $\alpha$ from zero, the inversemass vanishes at $\alpha=1/4$ and it increases monotonically from zero for$\alpha \geq 1/4$. By deriving an effective low-energy theory of the dilute gasof fermions, we demonstrate that the Drude weight $K_{\rm th}$ of the thermalconductivity exhibits a similar dependence on $\alpha$ near the saturationfield. Moreover, this theory predicts a transition between a two-componentTomonaga-Luttinger liquid and a vector-chiral phase at a critical value$\alpha=\alpha_c$ that agrees very well with previous density matrixrenormalization group results. We also show that the resulting curve $K_{\rmth}(\alpha)$ is in excellent agreement with exact diagonalization (ED) results.Our ED results also show that $K_{\rm th}(\alpha)$ has a pronounced minimum at$\alpha\simeq 0.7$ and it decreases for sufficiently large $\alpha$ at lowermagnetic field values. We also demonstrate that the thermal conductivity issignificantly affected by the presence of magnetothermal coupling.

Large magnetic thermal conductivity induced by frustration in low-dimensional quantum magnets