December 11 2018

11 till 13.12.2018: Visit of Dr. Jad C. Halimeh ( MPI Dresden and TU Munich)

Dr. Jad C. Halimeh (MPI Dresden and TU Munich) will visit us from Tuesday 11.12.2018 to Thursday 13.12.2018 .

He will give a talk in our group workshop on Tuesday 11.12.2018 at 9:15 in room 4.18.

Quasiparticle origin of dynamical quantum phase transitions

We consider one- and two-dimensional Ising models with varying interaction ranges. Using matrix product state techniques, we study the dynamics of these systems and show a direct connection between the type of lowest-energy quasiparticles in the spectrum of the quench Hamiltonian and the type of nonanalyticities occuring in the Loschmidt return rate, a dynamical analog of the free energy. Our results also show a clear connection between the type of nonanalyticities and the phase of the long-time steady state in addition to how the order parameter decays at intermediate times. In particular, we discuss anomalous nonanalyticities that occur with no underlying local signature in the order parameter dynamics, unlike the traditional regular nonanalyticities that always correspond to a zero crossing of the order parameter. We demonstrate how dynamical quantum phase transitions can be used to extract the equilibrium physics of the model from short-time dynamics.

Furthermore he will give a talk in the Ctrl-Q seminar on Wednesday 12.12.2018 at 9:00 in room E.2.6.

Aging dynamics in quenched noisy long-range quantum Ising models

We consider the d-dimensional transverse-field Ising model with power-law interactions J/rd+σ in the presence of a noisy longitudinal field with zero average. We study the longitudinal-magnetization dynamics of an initial paramagnetic state after a sudden switch-on of both the interactions and the noisy field. While the system eventually relaxes to an infinite-temperature state with vanishing magnetization correlations, we find that two-time correlation functions show aging at intermediate times. Moreover, for times shorter than the inverse noise strength κ and distances longer than a(J/κ) 2/σ with a being the lattice spacing, we find a critical scaling regime of correlation and response functions consistent with the model A dynamical universality class with an initial-slip exponent θ = 1 and dynamical critical exponent z = σ/2. We obtain our results analytically by deriving an effective action for the magnetization field including the noise in a non-perturbative way. The above scaling regime is governed by a non-equilibrium fixed point dominated by the noise fluctuations.

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