Impact of a Movable System-Bath Boundary on Photon and Phonon Correlations and Quantum Information in Hierarchically Modelled Open Systems.

Humphries, Ben (2023) Impact of a Movable System-Bath Boundary on Photon and Phonon Correlations and Quantum Information in Hierarchically Modelled Open Systems. Doctoral thesis, University of East Anglia.

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Abstract

Non-perturbative methods are a powerful way of modelling open quantum systems (OQS). One such approach employed in chemical physics is the hierarchical equations of motion (HEOM). The flagship result of this thesis is the derivation of a new form of HEOM termed the Lorentz-Drude Undamped Oscillator HEOM (LDUO-HEOM), which is presented in the penultimate chapter. Preceding this is an analysis of historical methods of OQS (chapter 2) and the studies that have led to the realisation of the need for the LDUO-HEOM approach (chapters 3 and 4). Two different models are developed to establish the impact of keeping a molecular vibration in the Hamiltonian or moving it to the bath by modelling a simple molecular system. This is quantified through quantum information and quantum correlation metrics. Here 2D spectral lineshape is linked to non-Markovian memory effects. It is shown that the ellipticity of the peaks and the degree of non-Markovianity increase sharply when coupled to overdamped environments, or more gradually in underdamped environments, but with underdamped environments giving rise to greater non-Markovianity overall. We show that auxiliary density operators (ADOs) contain fundamental physical information that can offer new insight for terminating the HEOM, by reshaping the hierarchy volume to minimise the number of ADOs. Furthermore, second order quantum correlations are analysed. It is shown that phonon transitions modulate photon correlations at the vibrational mode frequency for continuously driven systems. If instead, the system is driven by a femtosecond pulsed laser we can see regions of intense vibrational stimulation within the correlations. The above methodologies are then applied to more complex systems such as molecular dimers. Finally, we present an analysis of the derived LDUO-HEOM through benchmark calculations of 2D electronic spectra and show it is a useful tool for modelling vibronic effects in ultrafast 2D spectroscopy.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Chemistry
Depositing User:	Chris White
Date Deposited:	16 Apr 2024 09:50
Last Modified:	16 Apr 2024 09:50
URI:	https://ueaeprints.uea.ac.uk/id/eprint/94907
DOI:

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