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A Review on Quantum Disentangled Liquid Phase

Negahdari, Mohammad Kazem | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51463 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Langari, Abdollah
  7. Abstract:
  8. Thermalization or the approach to thermal equilibrium in isolated many-body quantum systems is a fundamental problem in quantum statistical physics. There are various quantum systems, whose properties can be described on the basis of statistical mechanics, but there are also systems in which the thermal equilibrium is not realized.Those, that are integrable or systems that exhibit many-body localization (MBL) due to strong disorder, represent non-thermalized phase. Recent theoretical studies have revealed that integrability and the existence of a static disorder are not necessary conditions for the violation of thermalization, while there are translationally invariant and non-integrable systems that do not thermalize in the conventional sense. One of these cases is “Quantum Disentangled Liquid” (QDL). QDL is a finite temperature phase of translationally invariant quantum liquid consisting of heavy and light degrees of freedom. The basic characteristic of the QDL phase is that, while the heavy degrees of freedom are fully thermalized, the light ones satisfy an area law entanglement entropy (EE) for a typical fixed configuration of the heavy particles. This suggests that the light particles are “localized” by the heavy particles.Thus, in QDL thermal equilibration is incomplete and it is not a fully ergodic phase, where we are faced with partial breakdown of thermalization in a translational invariant system. Qualitative diagnostic to identify this phase is the bipartite EE after a projective measurement of the heavy degrees of freedom. In this thesis, we intend to understand the essence of QDL and review the literature in this area. Finally, in order to answer the question of whether QDL can be found in the Luttinger liquid (LL), we reviewed the Luttinger liquid theory. In the LL, there is an interesting property called the charge-spin separation, in which charge and spin excitations propagate with different velocities, which can be interpreted as different masses for charge and spin excitations, heavy and light counterparts
  9. Keywords:
  10. Entanglement Entropy ; Quantum Thermalization ; Non-Equilibrium Systems ; Disorder Free Localization ; Quantum Disentangled Liquid (QDL)

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