Disorder

Discovery of a Mechanism for Dislocation Nucleation and Migration Driven by Surface Segregation

  • By Burcu Ozden
  • 6 December 2017

Judith C. Yang and her colleagues answered the question of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems on their recently published article on Nature Materials. n this study, Judith Yang and her colleagues showed that atomic segregation acts as a source for generating dislocations for the first time. They have used Cu–Au alloy system for studying surface segregation. Real-time transmission electron microscopy (TEM) was used to both spatially and temporally resolve the transition of the coherent, dislocation free interface between a Cu3Au-segregated surface and a Cu(Au) crystal substrate into a semi-coherent structure through the nucleation and subsequent migration of misfit accommodating dislocations. They combined their experimental study with the teory by using density functional theory (DFT) and molecular dynamics (MD) simulations. They discovered a mechanism for dislocation nucleation and migration driven by surface segregation of solute atoms in a solid solution. Their results show that the surface-segregation-induced composition variations act as the source of strain/stress that drives the nucleation and migration of misfit dislocations, and demonstrate how the surface segregation phenomenon of an alloy constituent can be employed for developing atomistic insight into understanding the formation processes of misfit-accommodating dislocations.

Many Body Localisation with Weak Disorder in the Quantum East Model

Speaker(s): 
Philip Crowley
Dates: 
Thursday, September 22, 2016 - 4:00pm to 6:00pm

Recent research has shown the Many-Body Localised phase to be a robust state of matter, thus furthering renewed interest in the quantum dynamics of closed systems. The existence of this non-thermalising phase is now well established in sufficiently low-dimensional and disordered systems. However the possibility of a many-body localised phase in the absence of static disorder remains an interesting prospect.

We study a kinetically constrained spin model with a putative disorder-free localisation transition and characterise the different...