Speaker: Atsushi Ueda (Institute for Solid State Physics)

Date & Time: 10am, May 16, 2022.

Title: Tensor network renormalization study on the crossover in classical Heisenberg and RP2 models in two dimensions

Abstract:

The Berezinskii-Kosterlitz-Thouless (BKT) transition in the classical XY model is a milestone for studying topological phase transitions. The U(1) spin configuration allows the topological defects (vortex-antivortex) with integer charge, and its phase transition mechanism is currently well understood. In contrast to the remarkable success of the XY model, the nature of the topological dynamics with the other types of topological defects remains elusive. In particular, the Lebwohl-Lasher (LL) and the antiferromagnetic Heisenberg model on the triangular lattice host Z2 vortices thanks to the Z2-valued fundamental group of the target space. However, after decades of discussion, the existence/universality class of the BKT-type transitions in those models has been inconclusive.

In this talk, I will introduce our recent approach to 2D classical systems using tensor network and conformal field theory and discuss the possible scenarios of Z_2 vortex-triggered phase transitions.