Rostock 2019 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
Q: Fachverband Quantenoptik und Photonik
Q 61: Quantum Effects (Cavity QED)
Q 61.1: Vortrag
Freitag, 15. März 2019, 10:30–10:45, S Gr. HS Maschb.
Dynamical Critical Scaling of Long-Range Interacting Quantum Magnets — •Nicolò Defenu1, Tilman Enss1, Michael Kastner2, and Giovanna Morigi3 — 1Institut für Theoretische Physik, Universität Heidelberg, D-69120 Heidelberg, Germany — 2National Institute for Theoretical Physics (NITheP), Stellenbosch 7600, South Africa — 3Theoretische Physik, Universität des Saarlandes, D-66123 Saarbrücken, Germany
Slow quenches of the magnetic field across the paramagnetic-ferromagnetic phase transition of spin systems produce heat. In systems with short-range interactions the heat exhibits universal power-law scaling as a function of the quench rate, known as Kibble-Zurek scaling. In this work we analyze slow quenches of the magnetic field in the Lipkin-Meshkov-Glick (LMG) model, which describes fully connected quantum spins. We analytically determine the quantum contribution to the residual heat as a function of the quench rate δ by means of a Holstein-Primakoff expansion about the mean-field value. Unlike in the case of short-range interactions, scaling laws in the LMG model are only found for a ramp starting or ending at the critical point. If instead the ramp is symmetric, as in the typical Kibble-Zurek scenario, then the number of excitations exhibits a crossover behavior as a function of δ and tends to a constant in the thermodynamic limit. Previous, and seemingly contradictory, theoretical studies are identified as specific limits of this dynamics. Our results can be tested on several experimental platforms, including quantum gases and trapped ions.