Theoretical Physics Seminar: Alexios Michailidis (Leeds)

Date: 7 July 2017
Time: 14:00 to 15:00
Location: EC Stoner 8.201
Speaker: Alexios Michailidis (Leeds)

Title: Arbitrarily slow dynamics in disorder-free many-body systems

Abstract: Quantum many-body systems are known to exhibit a dynamical phase transition to a non-ergodic phase known as many-body localization (MBL). MBL systems feature vanishing conductivity and a logarithmic information spreading (S ∼ ln(t)), unlike typical many-body systems where conductivity is finite and information spreads ballistically (S ∼ t). An MBL system can be understood as the analogue of Anderson insulator in the presence of interactions. MBL phase is thus tied to the presence of disorder in the system. An active area of research is understanding whether disorder is an essential ingredient for localization, or whether an interaction-induced MBL phase is possible [1-3]. We identify a class of strongly sub-diffusive, MBL-like systems by studying the spreading of information after a global quench using matrix product state formalism. For the time-scales of any practical purpose these systems are indistinguishable from MBL systems [4]. Using time-dependent degenerate perturbation theory (tDPT), we study the magnetization decay in the system for different orders of tDPT. We identify the critical order where the dynamics induced by the perturbed Hamiltonian are enough to delocalize the system. This method provides new insight on the mechanism of delocalization of disorder-free systems.

[1] W. De Roeck and F. Huveneers, Communications in Mathematical Physics 332, 1017 (2014)
[2] M. Schiulaz et al. , Phys. Rev. B 91, 184202 (2015)
[3] N. Y. Yao et al., Phys. Rev. Lett. 117, 240601 (2016)
[4] Alexios A. Michailidis et al., arXiv: 1706.05026 (2017)