Phase Transitions of Frustrated XY spins in Two Dimensions

The row model is used to study the commensurate-incommensurate (C-IC) an isotropic (FFTXY) transitions of the frustrated 2D XY model on the triangular lattice. New relevant variables clarify the physics of these transitions: phase and chiral variables are coupled so that spin waves generate long range polar interactions. The resulting dielectric constan diverges at the transition. A single transition occurs for the FFTXY model; in the C-IC regime the Lifshitz point is at T=0 and the C phase i a Smectic-A like phase which disorders via a 2D nematic-smectic-A transition.