Dr. Xin Cao
Xin studied physics at Peking University, Beijing from 2008 to 2012, there he got his Bachelor degree with an experimental thesis “Metal Oxide Thin Film Synthesis by Pulsed Laser Deposition”. He then studied at the Hong Kong University of Science and Technology and finished his master thesis “Phase-space Networks of Spin Glasses” in 2014. He stayed at the same group for his PhD degree but changed his research from computational physics to experimental soft condensed matter physics, he finished his thesis “Surface Relaxation of Vapour-depositing Colloidal Glass and the Microscopic friction” in December 2017. Xin joined Bechinger group at the University Konstanz as a visiting student in October 2017 and now is a Humboldt Postdoc Fellow of the group.
Xin’s current research focus on understanding the microscopic friction or nano friction by using colloid model system. The colloidal particles mimic the atomic particles in the sense that they obey the same statistical rules. Since colloidal particles are large and slow enough so that their positions could be tracked as a function of time, this facilitates our understanding of physical phenomenon at atomic scale. By externally driving a colloidal monolayer crystal on top of a periodic energy landscape, the frictional response of the monolayer crystal can be studied. Static friction exists when the lattice constant of the monolayer crystal is commensurate with that of the periodic energy landscape or when the energy barrier height is large enough on the landscape, topological excitations (such as kinks and antikinks) plays a crucial role in this case for the mobility of the monolayer. On the other hand, when the two lattice constant are incommensurate to one another and the energy barrier is lower than a critical value, the monolayer can smoothly slide on the energy landscape even by applying an infinitesimal force. This research provides guidelines to the fabrication of nano mechanical devices where the surface to bulk ratio is large, it also helps understanding a range of phenomenon with non-linear response, where the topological excitations plays important roles.
7. Cao, X., Silva, A., Panizon, E., Vanossi A., Manini, N., Tosatti, E., Bechinger C. Moire-pattern evolution couples rotational and translational friction at crystalline interfaces Phys. Rev. X, 12, 012059 (2022)
6. Cao, X., Panizon, E.,Vanossi A., Manini, N., Tosatti, E., Bechinger C. Pervasive orientational and directional locking at geometrically heterogeneous sliding interfaces Phys. Rev. E 103, 012606 (2021)
5. Cao, X., Panizon, E., Vanossi, A., Manini, N., Tosatti, E., Bechinger, C. Pile-up transmission and reflection of topological defects at grain boundaries in colloidal crystals Nat. Commun, 11, 3079 (2020)
4. Cao, X., Panizon, E., Vanossi, A., Manini, N., Bechinger, C. Orientational and directional locking of colloidal clusters driven across periodic surfaces. Nat. Phys. 15, 776–780 (2019)
3. Cao, X., Zhang, H. & Han, Y. Release of free-volume bubbles by cooperative-rearrangementregions during the deposition growth of a colloidal glass. Nat. Commun. 8, 362 (2017) .
2. Su, Y., Lai, P. Y., Ackerson, P. J., Cao, X., Han, Y. & Tong, P. Colloidal diffusion over aquasicrystalline-patterned surface. J. Chem. Phys. 146, 214903 (2017) .
1. Cao, X., Wang, F. & Han, Y. Ground-state phase-space structures of two-dimensional +-Jspin glasses: A network approach. Phys. Rev. E 91, 062135 (2015) .