Stolpp, Jan; Zhang, ShangShun; HeidrichMeisner, Fabian; Batista, Cristian D.
(2019):
Large magnetic thermal conductivity induced by frustration in lowdimensional quantum magnets.
In: Physical Review B, Vol. 99, No. 13, 134413

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Abstract
We study the magnetic fielddependence of the thermal conductivity due to magnetic excitations in frustrated spin1/2 Heisenberg chains. Near the saturation field, the system is described by a dilute gas of weakly interacting fermions (freefermion fixed point). We show that in this regime the thermal conductivity exhibits a nonmonotonic behavior as a function of the ratio alpha = J(2)/J(1) between second and firstnearestneighbor antiferromagnetic exchange interactions. This result is a direct consequence of the splitting of the singleparticle dispersion minimum into two minima that takes place at the Lifshitz point alpha = 1/4. Upon increasing a from zero, the inverse mass vanishes at alpha = 1/4 and it increases monotonically from zero for alpha >= 1/4. By deriving an effective lowenergy theory of the dilute gas of fermions, we demonstrate that the Drude weight Kth of the thermal conductivity exhibits a similar dependence on a near the saturation field. Moreover, this theory predicts a transition between a twocomponent TomonagaLuttinger liquid and a vectorchiral phase at a critical value alpha = alpha(c) that agrees very well with previous density matrix renormalization group results. We also show that the resulting curve Kth (alpha) is in excellent agreement with exact diagonalization (ED) results. For the lowmagnetic field regime, our ED results show that Kth (alpha) has a pronounced minimum at alpha similar or equal to 0.7. We also demonstrate that the thermal conductivity is significantly affected by the presence of magnetothermal coupling.