Abstract: Spontaneous symmetry breaking is a fundamental principle of nature. It explains many emergent properties of condensed matter systems, like long range magnetic order or superconductivity, but it also explains the origin of mass in elementary particles. The 2013 Nobel Prize in Physics to Englert and Higgs is the latest tribute to this general principle. In this talk I will discuss some interesting properties of graphene and its double layer cousin on the light of symmetry breaking induced by electron-electron interactions. I will start with graphene at weak coupling where, instead of symmetry breaking, one encounters an interesting example of emergent symmetry as the energy is lowered. Spontaneous symmetry breaking occurs at strong coupling, where several phases compete as a consequence of the details of the interaction. Graphene double layer, on the other hand, is unstable even at weak coupling; a clear example where more is indeed different. The possible low energy symmetry breaking phases for this system and related experimental results will be discussed.
Place: Physics Dept. Meeting Room, 2th floor, IST