Large thermomagnetic effects in weakly disordered Heisenberg chains

Some of the most fascinating manifestations of quantum many-body physics in one-dimension (1D) can be found in spin- 1 chain systems 1,2 . In particular, the spin- 1 Heisenberg model with antiferromagnetic nearest neighbor exchange interactions is one of the most extensively studied paradigms. It provides a remarkably non– trivial example of an exactly solvable model 3 , allowing a detailed analysis of its thermodynamic properties. While integrability is special to this particular model, its low energy properties are generic: they do not differ essentially from low energy properties of other (non integrable) spin chain models, with more general finite range interactions. In essence, these systems support Fermionic elementary excitations – spinons – which carry spin and no charge. Their kinetic energy and interactions are dictated by the exchange couplings in the chain, and their Fermi momentum can in principle be tuned by a magnetic field B, which plays the role of a chemical potential.