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On the difference between thermalization in open and isolated quantum systems: a case study

by Archak Purkayastha, Giacomo Guarnieri, Janet Anders, Marco Merkli

Submission summary

Authors (as registered SciPost users): Archak Purkayastha
Submission information
Preprint Link: https://arxiv.org/abs/2409.11932v1  (pdf)
Date submitted: 2024-09-29 03:07
Submitted by: Purkayastha, Archak
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Condensed Matter Physics - Theory
  • Quantum Physics
  • Statistical and Soft Matter Physics
Approach: Theoretical

Abstract

Thermalization of isolated and open quantum systems has been studied extensively. However, being the subject of investigation by different scientific communities and being analysed using different mathematical tools, the connection between the isolated (IQS) and open (OQS) approaches to thermalization has remained opaque. Here we demonstrate that the fundamental difference between the two paradigms is the order in which the long time and the thermodynamic limits are taken. This difference implies that they describe physics on widely different time and length scales. Our analysis is carried out numerically for the case of a double quantum dot (DQD) coupled to a fermionic lead. We show how both OQS and IQS thermalization can be explored in this model on equal footing, allowing a fair comparison between the two. We find that while the quadratically coupled (free) DQD experiences no isolated thermalization, it of course does experience open thermalization. For the non-linearly interacting DQD coupled to fermionic lead, we show by characterizing its spectral form factor and level spacing distribution, that the system falls in the twilight zone between integrable and non-integrable regimes, which we call partially non-integrable. We further evidence that, despite being only partially non-integrable and thereby falling outside the remit of the standard eigenstate thermalization hypothesis, it nevertheless experiences IQS as well as OQS thermalization.

Author indications on fulfilling journal expectations

  • Provide a novel and synergetic link between different research areas.
  • Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
  • Detail a groundbreaking theoretical/experimental/computational discovery
  • Present a breakthrough on a previously-identified and long-standing research stumbling block
Current status:
In refereeing

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