THERMODYNAMICS OF FRUSTRATED QUANTUM SPIN CHAINS

We apply the transfer-matrix density matrix renormalization group (DMR G) approach to frustrated quantum spin chains, down to T = 0.025 K in the thermodynamic limit. The incommensurability problem of exact diago nalization and the negative sign problem of quantum Monte Carlo vanish completely. For illustration, we give results for chains with next-ne arest-neighbor frustration and for the delta chain, which has been a t estbed for many thermodynamic methods. The DMRG approach proves to be an extremely powerful method for the old problem of the thermodynamics of frustrated systems.