Magnetothermal transport in spin-ladder systems

Abstract

We study a theoretical model for the magnetothermal conductivity of a spin-1 2 ladder with low exchange coupling (J ΘD) subject to a strong magnetic field B. Our theory for the thermal transport accounts for the contribution of spinons coupled to lattice phonon modes in the onedimensional lattice. We employ a mapping of the ladder Hamiltonian onto an XXZ spin-chain in a weaker effective field B ef f = B − B0, where B0 = B c1 +B c2 2 corresponds to half-filling of the spinon band. This provides a low-energy theory for the spinon excitations and their coupling to the phonons. The coupling of acoustic longitudinal phonons to spinons gives rise to hybridization of spinons and phonons, and provides an enhanced B-dependant scattering of phonons on spinons. Using a memory matrix approach, we show that the interplay between several scattering mechanisms, namely: umklapp, disorder and phonon-spinon collisions, dominates the relaxation of heat current. This yields magnetothermal effects that are qualitatively consistent with the thermal conductivity measurements in the spin-1 2 ladder compound Br4(C5H12N)2 (BPCB).

Crystal Structure, Physical Properties, and Electronic and Magnetic Structure of the Spin S = 5/2 Zigzag Chain Compound Bi2Fe(SeO3)2OCl3

“…Finally, the practical aspect of the quasi-one-dimensional magnetic systems is the possibility of significant enhancement of thermal conductivity in well-defined directions, i.e. along spin chains − or spin ladders, , in basically three-dimensional crystal lattices. This enhancement in quantum spin systems is attributed to the large contribution of magnetic excitations.…”

Plaquette order in a dimerized frustrated spin ladder

“…Moreover, the Debye temperature in NOCuNO is of the same order of magnitude as the spin exchange interactions. It is known that when these two energy scales are comparable, the spin-lattice coupling is enhanced 17,18 . These observations motivate the study of the effect of spin-lattice coupling, which was not considered in earlier theoretical studies of the NT model.…”