Dresden 2020 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 23: Nonequilibrium Quantum Many-Body Systems 1 (joint session TT/DY)

TT 23.2: Talk

Tuesday, March 17, 2020, 09:45–10:00, HSZ 204

Slow quantum thermalization and many body revivals from mixed phase space — •Alex Michailidis¹, Chris Turner², Dimitry Abanin³, Zlatko Papic², and Maksym Serbyn¹ — ¹IST Austria, Klosterneuburg, Austria — ²University of Leeds, Leeds, United Kingdom — ³University of Geneva, Geneva, Switzerland

Isolated, interacting quantum systems thermalize when local measurements are distributed according to the Gibbs ensemble. The ability of an isolated quantum many body system to thermalize is tied to the absence of an extensive set of integrals of motion. The thermalization rate may, however, depend strongly on the initial state. A class of kinetically constraint systems [Nat. Phys. 14, 745 (2018)] displays such features, due to a set of quasi-eigenmodes, known as ``quantum many body scars", which form a slowly thermalizing subspace. The slow thermalization is also associated to an unstable periodic orbit in a slightly entangled manifold of matrix product states (MPS) [PRL 122, 040603 (2019)] .

First, by using tensor tree states (TTS) and ideas from standard mean field theory, we generalize the MPS ansatz to higher dimensions. We employ the time-dependent-variational-principle to analytically calculate the equations of motion for lattices of arbitrary connectivity. We find that the coherent oscillations in the quantum system are associated to stable periodic orbits in a mixed phase space. This method provides a new way to identify entangled states which display coherent dynamics. Finally, we associate slowly thermalizing states to regular ``islands" in the mixed phase space.