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Phonon dressing of a facilitated one-dimensional Rydberg lattice gas

by Matteo Magoni, Paolo P. Mazza, Igor Lesanovsky

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Submission summary

Authors (as registered SciPost users): Matteo Magoni
Submission information
Preprint Link: https://arxiv.org/abs/2104.11160v3  (pdf)
Date accepted: 2022-07-29
Date submitted: 2022-07-25 13:01
Submitted by: Magoni, Matteo
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Atomic, Molecular and Optical Physics - Theory
  • Condensed Matter Physics - Theory
  • Quantum Physics

Abstract

We study the dynamics of a one-dimensional Rydberg lattice gas under facilitation (anti-blockade) conditions which implements a so-called kinetically constrained spin system. Here an atom can only be excited to a Rydberg state when one of its neighbors is already excited. Once two or more atoms are simultaneously excited mechanical forces emerge, which couple the internal electronic dynamics of this many-body system to external vibrational degrees of freedom in the lattice. This electron-phonon coupling results in a so-called phonon dressing of many-body states which in turn impacts on the facilitation dynamics. In our theoretical study we focus on a scenario in which all energy scales are sufficiently separated such that a perturbative treatment of the coupling between electronic and vibrational states is possible. This allows to analytically derive an effective Hamiltonian for the evolution of consecutive clusters of Rydberg excitations in the presence of phonon dressing. We analyze the spectrum of this Hamiltonian and show -- by employing Fano resonance theory -- that the interaction between Rydberg excitations and lattice vibrations leads to the emergence of slowly decaying bound states that inhibit fast relaxation of certain initial states.

Published as SciPost Phys. Core 5, 041 (2022)


Reports on this Submission

Anonymous Report 1 on 2022-7-27 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:2104.11160v3, delivered 2022-07-27, doi: 10.21468/SciPost.Report.5463

Strengths

Please see the earlier report.

Weaknesses

Please see the earlier report.

Report

I thank the Authors for their detailed reply to my earlier report. I believe, there have been a few misunderstandings that may arise from my inadequate choice of wordings. Below, I reply to the Authors’ comments in details.

1. I agree that the results presented in Sec. 4 and 5, can only be guessed beforehand once the effective Hamiltonian is known, and not from the initial interacting Hamiltonian. In my earlier report, I stressed this point couple of times that the derivation of the simple effective Hamiltonian from the initial complicated Hamiltonian is the main result of the Manuscript, which I find very elegant and interesting, and therefore must deserve a publication in some form on its own. However, as a reader, after going through the derivation of Sec. 3 and the form of the effective Hamiltonian, the results of Sec. 4 and 5 do not stand-out on their own, as they are derived from the effective Hamiltonian itself, and not from the full Hamiltonian (specifically, the inhibition dynamics of Sec. 4). Moreover, there is no comparison presented between the dynamics of the full Hamiltonian and that of the effective one, especially for $\kappa/\omega = 0.5$ (Fig. 3 bottom panel), as this choice of $\kappa/\omega$ is close to the borderline of the validity of the perturbative calculation.


2. I am still unconvinced about the generality in the choice of system parameters, as they must follow stringent conditions for the perturbative treatment to be valid.


3. I understand, my choice of the word ‘thermodynamic limit’ have caused some confusions. My concern about the ‘thermodynamic limit’ was not about the Hamiltonians (effective or the original one). I was concerned, as the number of excitations (or energy) in the initial cluster-1 (single cluster of size 1) state does not grow linearly with system-size. But, now I understand that this is not an issue, as the extensivity of the initial state is not required for the ballistic growth of the cluster-size, but only required for a thermalizing dynamics (which is beyond the scope of the present manuscript, of course). However, as I said in the earlier report, the initial states having cluster of size 1 are very special. The number of such states only grows linearly with the system-size, while the atom-only Hilbert space dimension grows as $\sim N^2$ without considering the local phonon degrees of freedom. Rest of the states follow ballistic dynamics as seen in the manuscript. Therefore even a small perturbation in the initial state, and/or small couplings to other states (that are ignored in the perturbative expansion) may hinder the inhibition to the ballistic growth, resulting in ballistic (or may be even thermalizing) dynamics. In experiments, getting rid of such small perturbations from the pure cluster-1 state can indeed be very difficult.


3. In the minor points, the comment about the thermodynamic limit of the band structure was not about that of the effective Hamiltonian, but about the full Hamiltonian of Eq. 7. I should have been more clear. I apologize to the Authors for that. Specifically, I was curious whether the appearance of the bound state in the band structure (of Hamiltonian Eq. 7), as seen in the bottom panels of Fig. 2, survives large size limit or not.

To summarize, I stand by my earlier assessment, as the manuscript, in its present form, in my opinion, does not meet the acceptance criteria of SciPost Physics.

  • validity: good
  • significance: ok
  • originality: good
  • clarity: top
  • formatting: excellent
  • grammar: excellent

Author:  Matteo Magoni  on 2022-07-27  [id 2691]

(in reply to Report 1 on 2022-07-27)

We thank the Referee for their detailed reply.
Given their report and their previous recommendation for publication on SciPost Physics Core, we would proceed in resubmitting the manuscript to SciPost Physics Core.

Best regards,
Matteo Magoni and Igor Lesanovsky

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