Smecticlike phase for modulated XY spins in two dimensions

Abstract

The row model for frustrated XY spins on a triangular lattice in 2D is used to study incommensurate{IC}) spiral and commensurate{C} antiferromagnetic (AF) phases, in the regime where a C-IC transition occurs. Using fluctuating boundary conditions and specific histogram techniques, a detailed Monte Carlo (MC) study reveals more structure in the phase diagram than found in previous MC simulations of the full parameter space. On the (C) side, equilibrium configurations consist of alternating stripes of spiral phases of opposite chirality separated by walls of the (C) phase. For this same parameter regime, thermodynamic quantities are computed analytically using the NSCHA, a generalization of the self consistent harmonic approximation appropriate for chiral systems. On the commensurate side of the (C)-(IC) boundary, NSCHA predicts an instability of the (C) phase. This suggests that the state is spatially inhomogeneous, consistent with the present MC result: it resembles the smectic-A phase of liquid crystals, and its existence implies that the Lifshitz point is at $T=0$ for modulated XY spins in 2D. The connection between frustrated XY systems and the vortex state of strong type II superconductors suggests that the smectic phase may correspond to a vortex liquid phase of superconducting layers.

Single Postscript file containing 24 pages of text and 8 figures. To appear in May 1 issue of Phys. Rev. B, Vol. 57

References in corpus (11)

• Two phase transitions in the fully frustrated $XY$ model
• Vortex Line Fluctuations in Model High Temperature Superconductors
• A Renormalization Group Study of Helimagnets in D=2+EPSILON Dimensions
• Vortex lattce melting in 2D superconductors and Josephson arrays
• Superconducting Coherence in a Vortex Line Liquid; Simulations with Finite λ
• Comment on "Two Phase Transitions in the Fully frustrated XY Model"
• Phase transitions in a frustrated XY model with zig-zag couplings
• Helicity Modulus and Meissner Effect in a Fluctuating Type II Superconductor
• Thermal excitations of frustated XY spins in two dimensions
• Spin Diffusion in 2D XY Ferromagnet with Dipolar Interaction
• Bounday Condition histograms for modulated phases

Cited by in corpus (1)

• Topological defects and critical phenomena in two-dimensional frustrated helimagnets