arXiv subjects

Paul E. Lammert

Publications and source records attributed to Paul E. Lammert.

38 records · Page 3Linked to original sources

arXiv1995

Topology and Nematic Ordering I: A Gauge Theory

We consider the weakly first order phase transition between the isotropic and ordered phases of nematics in terms of the behavior of topological line defects. Analytical and Monte Carlo results are presented for a new coarse-grained lattice theory of nematics which incorporates nematic inversion symmetry as a local gauge invariance. The nematic-isotropic transition becomes more weakly first order as disclination core energy is increased, eventually splitting into two continuous transitions involving the unbinding and condensation of defects, respectively. These transitions are shown to be in the Ising and Heisenberg universality classes. A novel isotropic phase with topological order occurs between them.

cond-mat↗

arXiv1995

Topology and Nematic Ordering II: Observable Critical Behavior

This paper is the second in a pair treating a new lattice model for nematic media. In addition to the familiar isotropic (I) and nematically ordered (N) phases, the phase diagram established in the previous paper (Paper I) contains a new, topologically ordered phase (T) occuring at large suppression of topological defects and weak nematic interactions. This paper (Paper II) is concerned with the experimental signatures of the proposed phase diagram. Specific heat, light scattering and magnetic susceptibility near both the N/T and I/T transitions are studied, and critical behavior determined. The singular dependences of the Frank constants ($K_1$, $K_2$, $K_3$) and the dielectric tensor anisotropy ($Δε$) on temperature upon approaching the N/T transition are also found.

cond-mat↗