Seminar "Topology and symmetry in triangular lattice Ising antiferromagnets" by Andrew Smerald

Seminar July 15th

• Speaker: Andrew Smerald, EPFL Lausanne
• Date: July 15h (Fri)
• Time: 15:00-16:00
• Venue: C016, Lab1

"Topology and symmetry in triangular lattice Ising antiferromagnets"

We investigate the triangular lattice Ising antiferromagnet with coupling beyond nearest neighbour, focussing in particular on the interplay between topology and symmetry. Using a specially designed Monte Carlo algorithm with directed loops, we show that a first-order phase transition from a low-temperature, broken-symmetry stripe state to the paramagnet can be split, revealing an intermediate nematic phase. Furthermore, we demonstrate the emergence of several properties of a more topological nature, such as fractional edge excitations in the stripe state, the proliferation of double domain walls in the nematic phase and the coexistence of a broken symmetry and algebraically decaying spin correlations. We investigate the nature of the second-order phase transition between the stripe and nematic phases and demonstrate that it is of the Kasteleyn type and in the Pokrovsky-Talapov universality class. Finally, we show that some of these concepts are relevant in dipolar coupled Ising antiferromagnets, and can therefore be realised in artificial nano-magnet arrays. 

********************************************************************************************

We hope many of you will attend the seminar.

TQM Unit