Berlin 2018 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 81: Nonequilibrium Quantum Many-Body Systems III

TT 81.2: Vortrag

Donnerstag, 15. März 2018, 09:45–10:00, H 3010

Constructing effective free energies for dynamical quantum phase transitions in the transverse-field Ising chain — •Daniele Trapin and Markus Heyl — Max-Planck-Institut fur Physik komplexer Systeme, Nothnitzer Strasse 38, 01187-Dresden, Germany

Phase transitions play a central role in equilibrium many-body systems. The theory of dynamical quantum phase transitions represents an attempt to extend the notion of phase transition to the far from equilibrium regime. As opposed to conventional transitions which are driven by a control parameter such as temperature of pressure, these dynamical transitions occur as a function of time with physical quantities becoming nonanalytic at critical times. While there are many formal analogies to conventional transitions, it is a major question to which extent it is possible to formulate a nonequilibrium counterpart to a Landau-Ginzburg theory. In this work we address this problem for quantum quenches in a one-dimensional transverse-field Ising model. We construct an effective free energy which due to unitary time evolution becomes a complex quantity. This transforms the conventional minimization principle into a saddle-point equation in the complex plane of the order parameter. We study this effective free energy in the vicinity of the dynamical quantum phase transition by performing an expansion in terms of the complex magnetization.