Doc. dr. Alenka Mertelj

Assist. Prof. Alenka Mertelj is a Senior researcher and Assistant Head of the Complex Matter Department at Jožef Stefan Institute. She investigates various soft matter systems and is also involved in educational activities by teaching and supervising the students at the Faculty of Mathematics and Physics, and Jožef Stefan International Postgraduate School. For her work, she received the International Liquid Crystal Society Mid-Career Award (2020), and the Zois Certificate of Recognition (2015).

Research programme: Light and matter
Training topic: An experimental study of the topology and dynamics of domain walls in ferroelectric liquids

Recently discovered ferroelectric nematic liquid crystals (FNLCs) are unique examples of liquid materials. They combine properties of ferroelectric solid-state materials, that play a very important role in numerous everyday devices as well as high technological applications ranging from piezoelectric sensing and dielectric energy storage to electrocaloric solid-state cooling, with those of nematic liquid crystals that are most renowned for optical applications such as LC displays and switchable optical components.

The distinctive properties of ferroelectric liquids that come from a combination of fluidity, ferroelectric order, and nematic elasticity, make them a unique physical system for fundamental studies linking the fields of soft matter, topology, and electrostatics.  Additionally, spontaneous polarization values of 0.05 As/m, large effective dielectric constant (>10000), and nonlinear optical coefficients (1-10 pV/m) in combination with nematic switchability make them very promising for applications, e.g., switchable elements in nonlinear optics or organic electronics as sensors or for energy harvesting.

The liquid nature of FNLCs manifests in unique ferroelectric domain structures of which integral parts are topological defects and for studies of the fundamental properties and exploitation of FNLCs in devices, an understanding of these structures is needed. The subject of the proposed Ph.D. thesis is an experimental investigation of mechanisms of formation of the domain walls and their response to external fields. The candidate will use the photo-patterning surface alignment technique to design different domain structures of which structure and topology will be studied by advanced linear and nonlinear optical microscopy techniques.  The realization and in-depth understanding of domain control will be a foundation for future studies and applications of the FNLC materials. Joined with comprehension of the topology of the system, this knowledge will pave the way for building topologically protected structures, for example, periodic structures for nonlinear optic devices or structures that maximize the mechano-electric effect, e.g. in vibrational energy harvesting or sensing.

The candidate will join the research group Light&Matter at the Complex Matter Department at Jožef Stefan Institute. The members of the group focus on different soft matter systems, and many of them are strongly involved in research of ferroelectric liquids from the very beginning of their discovery. The group members have strong international collaborations, among others with researchers from the UK, Belgium, Germany, Austria, Spain, Japan, and China. In the stimulating environment, the candidate will have the opportunity to gain up-to-date knowledge and skills and to participate in an international research network.