Implications of the low-temperature instability of dynamical mean-field theory for double-exchange systems

[摘要] The single-site dynamical mean field theory approximation to the double-exchange model is found to exhibit a previously unnoticed instability, in which a well-defined ground state which is stable against small perturbations is found to be unstable to large-amplitude but purely local fluctuations. The instability is shown to arise either from phase separation or, in a narrow parameter regime, from the presence of a competing phase. The instability is therefore suggested as a computationally inexpensive means of locating regimes of parameter space in which phase separation occurs.

[发布日期] 2005-12-01

[关键词] TO-POLARON CROSSOVER;INFINITE DIMENSIONS;PHASE-SEPARATION;MAGNETORESISTANCE;TRANSITION