Condensed Matter Physics Seminar
Date: Wednesday, April 26, 2017
Time: 4:00 PM
Location: PAB 4-330
Speaker: Professor Xie Chen (Caltech)
Title: “Out-of-Time-Ordered Correlator in Many-Body Localized Systems”
In many-body localized systems, propagation of information forms a light cone that grows logarithmically with time. However, local changes in energy or other conserved quantities are expected to spread only within a finite distance. Is it possible to detect the logarithmic light cone generated by a local perturbation A from the response of another local operator B at a later time? In this talk I will show that this is indeed the case, but only in an out-of-time-ordered way. In particular, we numerically calculate various correlators in a prototypical model of many-body localization. While the retarded correlator A(t = 0)B(t > 0) is not sensitive to the unbounded information propagation, the out-of- time-ordered correlator A(t = 0)B(t > 0)A(t = 0)B(t > 0) can detect the logarithmic light cone. We demonstrate the connection between the out-of-time-ordered correlator and the Lieb-Robinson bound in many-body localized systems, and explain how to saturate the latter by measuring the involved commutator on specially designed initial states.