# Topological classification of dynamical phase transitions

**Speaker:**S. Vajna , BU

**When:**September 23, 2015 (Wed), 12:00PM to 01:00PM (add to my calendar)

**Location:**SCI 328

**Hosted by:**Anatoli Polkovnikov

*This event is part of the Condensed Matter Theory Seminar Series. *

Astract: Dynamical phase transitions (DPT) are non-equilibrium phenomena occurring in systems following a quantum quench, and are characterized by nonanalytical time evolution of the dynamical free energy. First I introduce DPTs in the context of spin chains with particular focus on the quantum XY chain. Afterwards I generalize the problem for general 2-band systems in one and two dimensions (eg. SSH model, Kitaev-chain, Haldane model, p+ip superconductor, etc.), where we showed that the time evolution of the dynamical free energy is crucially affected by the ground state topology of both the initial and final Hamiltonians, implying DPTs when the topology is changed under the quench. The singularities of dynamical free energy in the 2D case are qualitatively different from those of the 1D case, the cusps appear only in the first time derivative.