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Efficiency of Excitonic Energy Transfer Phenomenon in Multi-Levels Quantum Systems

Nafari Qaleh, Zohreh | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55912 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Rezakhani, Ali
  7. Abstract:
  8. The process of energy transfer in quantum systems is an interesting phenomenon due to the emergence of quantum effects . This phenomena can be studied in one of two possible spaces : real space and energy space of the system . In addition , to evaluate how this process is successful , one can define an efficiency as the population of a target state . Finding the approaches to increase this quantity takes into account one of the main objectives of the current researches . On the other hand , isolating the quantum systems from the surrounding environment (bath) in practice is impossible and then interaction between them is inevitable . In this research , we provide a comprehensive study of the energy-transfer phenomena in order to populate a target energy level of three - and four-level quantum systems coupled to two thermal baths . Due to the system-environment interaction , such open quantum systems do not evolve unitarily described by Schr\"odinger equation . According to the relations between some time scales of the total system (main quantum system+environment) , one can derive a quantum master equation to describe the non-unitary evolution of an open quantum system . We consider here four quantum master equation to study the energy-transfer process in the multilevel open quantum system , i.e. , Lindblad , Floquet-Lindblad , Redfield and Floquet-Redfield master equation . The latter is one of the results of this research in which a special rotating wave approximation is applied . By considering the QED considerations , the Lamb-shift terms are also calculated in the last two master equations . These terms are due to the system-environment interaction and the external periodic agents applied to the system . With the help of these approaches , we examine the effects of an external periodic driving and the coherence induced by the environment on the energy transfer efficiency in the systems under study
  9. Keywords:
  10. Open Quantum System ; Energy Transfer ; Excitonic Energy Transfer ; Redfield Master Equation ; Lamb-Shift Effect ; Floquet Theorem ; Lindblad Master Equation

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