About this Research Topic
Soft matter includes materials that are easily deformed from polymers to gels, colloids and liquid crystals. The specific interactions that hold molecules together generally make them well sensitive to a multitude of external stimuli. Liquid crystals (LCs), for example, owe their success to their controllable meta-phases, ordered like solids, but fluid like liquids. However, interestingly, LCs exhibit slow relaxation dynamics as well as ultrafast femto- to pico-second dynamics. The physics of ultrafast dynamics in LC, and more generally in soft matter, remains yet largely unexplored.
Because of the wide range of systems belonging to the soft matter world, it is an inherently interdisciplinary field. This reflects the goal of this Research Topic: gathering a collection of scientific works from complementary disciplines, namely soft matter and ultrafast spectroscopy.
The main themes that compose the Research Topic will be:
• Soft Matter: Latest frontiers on material design and theory
o Colloids and topological structures: The role of fast and ultrafast processes in such dispersion and colloidal systems could open new interesting research directions.
o Soft matter photonics: Selected explored systems include cholesteric liquid crystal-based lasers, nematic tunable VCSEL lasers, topology tunable waveplates and light-matter coupled torque.
o Active matter: Active matter focuses on the role and consequences of the locomotion of diverse active agents at microscopic length scales. The pressing question would be, could - at least in principle- fast molecular and atomic processes affect or couple to the locomotion or general active matter dynamics?
• What about dynamics?
o Sub-nanosecond time scale: This is the typical time of LC order parameter (OP) dynamics which spans the ps- ns time scale. We focus on the slow OP dynamics in different geometries and confinement conditions.
o Picosecond time scale: In this time scale lattice vibration in solid-state, collective intermolecular dynamics in liquids and rotational motion of molecular gases can be observed. In this section, we concentrate on the experimental and theoretical efforts dedicated to the study of low energy excitations mainly triggered by light in the THz spectral range.
o Femtosecond time scale: where electronic dynamics becomes important and possible couplings to the nuclear dynamics can take place. While many techniques such as transient absorption, 2D infrared and visible spectroscopy, stimulated Raman scattering, CARS, and pump-probe spectroscopy allow for full characterization of the molecular response in soft matter, their detection sensitivity, dynamic range, and speed is far from optimum. In this section, we focus on advanced techniques to overcome these limitations.
o Towards attosecond chemistry of Soft Matter: The active exploration of the role of electronic coherences and the coupled electron-nuclear dynamics in Soft Matter requires time-resolved spectroscopic techniques with attosecond resolution, which is the natural time scale of electron motion. This subsection will focus on the latest works, both experimental and theoretical, in attosecond science dedicated to the investigation of the role of the electron dynamics in the photo-chemistry and photo-biology of complex systems, towards the future application in soft matter materials.
Keywords: soft matter, liquid crystal, ultrafast spectroscopy, THz radiation, attosecond chemistry
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