LAUSR

Phase transitions in softmatter systems reveal some of the interesting structural phenomena at the levels of individual entities constituting those systems. The relevant energy scales in softmatter systems are comparable to thermal energy (kBT∼10 J). This permits one to observe interesting structural dynamics even at ambient conditions. However, at the nanoscalemost experimental probes currently being used to study these systems have been either plagued by low sensitivity or are invasive atmolecular scales. Nitrogen-vacancy (NV) centers in diamond is emerging as a robust quantum probe for precisionmetrology of physical quantities (e.g.magnetic field, electric field, temperature, and stress). Here, we demonstrate by usingNV sensors to probe spin-fluctuations and temperature simultaneously to obtain information about controlled phase changes in a softmattermaterial as a function of temperature. The softmatter system chosen for the study is a standard liquid crystalline (LC)material which shows distinct phases close to room temperature. Individual NV centers at depths of a few nmare used as a probe to detectmagnetic signals emanating from a fewmolecular layers of sample on the surface of the diamond. The organization and collective dynamics of LCmolecules in nanoscopic volumes are discussed. Our study aims to extend the areas of application of quantum sensing usingNV centers to probe the softmatter systems, particularly those exhibitingmesophases and interesting interfacial properties.