CMT Forum: Jacob Robertson

28 Feb 2024
Seminars and colloquia
Simpkins Lee

Jacob Robertson (Oxford)

Seminar series
CMT Forum
Knowledge of physics?
Yes, knowledge of physics required
For more information contact

Quantum quenches in gapped spin-chains: mean-field theory and beyond

I will discuss the out of equilibrium dynamics following a shallow quantum quench in two spin chains. First, I will focus on the ANNNI model, a transverse field Ising chain with next-nearest neighbour interactions. The intermediate time dynamics of this model were explored in [1] which investigated the possibility of using quench dynamics to detect equilibrium quantum phase transitions. A simple mean-field study reproduces this result and allows for an easy criterion for the cutoff energy below which low-energy scaling behaviour is observed; it also allows us to estimate the correlation length at different times and show that it grows following the quench [2].

An unusual feature of the mean-field dynamics is that local observables do not relax to stationary values at late time. I will argue that this is a mean-field artefact by considering a second model, a staggered XXZ chain, and showing that a similar mean-field analysis gives similar long-lived oscillations and that these are damped when going one order perturbatively beyond mean-field theory [3]. This gives strong numerical evidence towards an open question of whether similar oscillations will decay in the tilted field Ising model.

[1] Haldar, Mallayya, Heyl, Pollmann, Rigol, Das, Phys. Rev. X 11, 031062 (2021)
[2] JR, Senese, Essler, SciPost Phys. 15, 032 (2023)
[3] JR, Senese, Essler,