Thermodynamics of frustrated quantum spin chains

We apply the transfer matrix DMRG to frustrated quantum spin chains, going down to T=0.025 while being in the thermodynamic limit. The incommensurability problem of exact diagonalization and the negative sign problem of quantum Monte Carlo vanish completely. To illustrate the method, we give results for chains with next-nearest neighbor frustration and the delta chain, which has been a testbed for many thermodynamic methods. By comparison, the DMRG proves to be an extremely powerful method for the old problem of the thermodynamics of frustrated systems.