Variational Study of Fermionic and Bosonic Systems with Non-Gaussian States: Theory and Applications

31.01.2018, 13:30

Dr. Tao Shi, Institute of Theoretical Physics  (Beijing, China) and Max Planck Institute of Quantum Optics (Garching)

We present a new variational method for investigating the ground state and out of equilibrium dynamics of quantum many-body bosonic and fermionic systems. Our approach is based on constructing variational wavefunctions which extend Gaussian states by including generalized canonical transformations between the fields. The key advantage of such states compared to simple Gaussian states is presence of non-factorizable correlations and the possibility of describing states with strong entanglement between particles. In contrast to the commonly used canonical transformations, such as the polaron or Lang-Firsov transformations, we allow parameters of the transformations to be time dependent, which extends their regions of applicability. Our formalism allows us not only to determine the energy spectrum of quasiparticles and their lifetime, but to obtain the complete spectral functions and to explore far out of equilibrium dynamics such as coherent evolution following a quantum quench. We illustrate and benchmark this framework with the non-equilibrium dynamics in the spin-boson and Kondo models.

Time and Place: Wednesday, 31st January, 13:30 h, Max Planck Institute for the Science of Light, Seminar Room A.1.500