Topological defects in nematic liquid crystals: playground of fundamental physics
1Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia
2Solid State Department, “Jožef Stefan” Institute, Jamova 39, Ljubljana, Slovenia
Topological defects (TDs) are an unavoidable consequence of continuous symmetry breaking phase transitions . They appear at all scales of physical systems, including particle physics, condensed matter and cosmology. Due to their topological origin they display several universalities that are independent of the systems’ microscopic details. For example, they might even explain the stability of “fundamental particles” via topological protection if ﬁelds represent a fundamental entity of nature . Furthermore, by invoking curvature inhomogeneities in spacetime , they could explain the nature of “dark matter” and “dark energy”.
Nematic liquid crystal (NLC) phase represent an ideal playground  to study TDs owing to their unique combination of optical anisotropy, fluidity and softness. In them various TDs could be relatively easily created, observed and manipulated. In the lecture our theoretical and experimental study of TDs in NLCs will be presented. We will demonstrate how a network of TDs forms due to the universal Kibble mechanism  and evolves with time after LC is quenched from the isotropic (ordinary liquid) to the nematic phase. Furthermore, we will show how different “charged” and “charge-less” TDs could be stabilized in confined nematics. In particular, defect structures analogous to intriguing Majorana particles  will be presented. Study of such structures might give insight into open problems in physics of neutrinos.
Figure: Time evolution of topological defects after the isotropic “island” is quenched below the isotropic-nematic continuous symmetry breaking phase transition temperature.
 W.H. Zurek, Cosmological experiments in condensed matter, Phys.Rep. 276, 177 (1996).
 A. Hobson, There are no particles, there are only fields, Am.J.Phys. 81, 241 (2013).
 J.T. Giblin et al., Departures from the Friedmann-Lemaitre-Robertson-Walker Cosmological Model in an Inhomogeneous Universe, Phys.Rev.Lett. 116, 251301 (2016).
 T.W.B. Kibble, Topology of cosmic domains and strings, J.Phys.A:Math.Gen. 9, 1387 (1976).
 F. Wilczek, Majorana returns, Nat.Phys. 5, 614 (2009).
host: Charles Rosenblatt