Quamtum Critical Dynamics in Many Body Systems

In the talk, motivated by recent experimental progresses, we shall take the challenge via an-alytically exploring finite temperature local spin dynamics in quantum E8 model emerging nearthe QCP of 1D transverse-field Ising model, zero-temperature nonlocal transverse spin dynamic-s in the quantum critical regime of XXZ Heisenberg model, and finite temperature dynamics atthe QCP of 3(space)+1(time) quantum ϕ4 model. During the exciting excursion, sophisticatedbut powerful theoretical tools were introduced and a bunch of new physics beyond conventionalpictures were discovered. Specifically, in quantum E8 model we found spin dynamics beyondconventional spin diffusion picture; in the XXZ Heisenberg model we discovered new dominantdynamic excitations completely beyond classic spinon picture; in the 3+1 quantum ϕ4 model, wefigured out dominant finite temperature dynamics at the QCP with an emerging “thermal” quasi-particle. At the end we shall also discuss the implication of our results for experiments in variousrelevant materials and suggest proper future experimental setups to test our theoretical findings.