PHASE-TRANSITIONS IN THE ONE-DIMENSIONAL FRUSTRATED QUANTUM XY MODEL AND JOSEPHSON-JUNCTION LADDERS

A one-dimensional quantum version of the frustrated XY (planar rotor) model is considered which can be physically realized as a ladder of Jo sephson junctions at half a flux quantum per plaquette. This system un dergoes a superconductor to insulator transition at zero temperature a s a function of charging energy. The critical behavior is studied usin g a Monte Carlo transfer matrix applied to the path-integral represent ation of the model and a finite-size-scaling analysis of data on small system sizes. Depending on the ratio between the interchain and intra chain couplings the system can have single or double transitions which is consistent with the prediction that its critical behavior should b e described by the two-dimensional classical XY-Ising model.