Spontaneous symmetry breaking in polar fluids.

Abstract

Spontaneous symmetry breaking and emergent polar order are each of fundamental importance to a range of scientific disciplines, as well as generating rich phase behaviour in liquid crystals (LCs). Here, we show the union of these phenomena to lead to two previously undiscovered polar liquid states of matter. Both phases have a lamellar structure with an inherent polar ordering of their constituent molecules. The first of these phases is characterised by polar order and a local tilted structure; the tilt direction processes about a helix orthogonal to the layer normal, the period of which is such that we observe selective reflection of light. The second new phase type is anti-ferroelectric, with the constituent molecules aligning orthogonally to the layer normal. This has led us to term the phases the <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>Sm</mi> <msubsup><mrow><mi>C</mi></mrow> <mrow><mi>P</mi></mrow> <mrow><mi>H</mi></mrow> </msubsup> </math> and SmA_AF phases, respectively. Further to this, we obtain room temperature ferroelectric nematic (N_F) and <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>Sm</mi> <msubsup><mrow><mi>C</mi></mrow> <mrow><mi>P</mi></mrow> <mrow><mi>H</mi></mrow> </msubsup> </math> phases via binary mixture formulation of the novel materials described here with a standard N_F compound (DIO), with the resultant materials having melting points (and/or glass transitions) which are significantly below ambient temperature. The new soft matter phase types discovered herein can be considered as electrical analogues of topological structures of magnetic spins in hard matter.