Related papers: Quantum phase transition of sub-Ohmic spin-boson models: An approach by the multiple Davydov D2 Ansatz

Quantum phase transition of sub-Ohmic spin-boson models: An approach by the multiple Davydov D2 Ansatz

URL: http://arxiv.org/abs/2510.11130v1
Date: Mon, 13 Oct 2025 08:21:09 GMT
Title: Quantum phase transition of sub-Ohmic spin-boson models: An approach by the multiple Davydov D2 Ansatz
Abstract summary: Ground state properties and quantum phase transitions of sub-Ohmic spin-boson models are investigated.<n>Three variants of the model are studied: (i) a single bath with diagonal coupling, (ii) two independent baths with diagonal and off-diagonal couplings, and (iii) a single bath with simultaneous diagonal and off-diagonal couplings.
Score: 4.7520642154428865
License: http://creativecommons.org/licenses/by/4.0/
Abstract: The ground state properties and quantum phase transitions of sub-Ohmic spin-boson models are investigated using the multiple Davydov D2 Ansatz in conjunction with the variational principle. Three variants of the model are studied: (i) a single bath with diagonal coupling, (ii) two independent baths with diagonal and off-diagonal couplings, and (iii) a single bath with simultaneous diagonal and off-diagonal couplings. For the purely diagonal model, the multiple Davydov D2 Ansatz yields critical coupling strengths that are consistent with other methodologies, validating its accuracy and efficiency. In the two-bath model, the competition between diagonal and off-diagonal couplings drives a first-order transition for both symmetric and asymmetric spectral exponents, with von-Neumann entropy showing a continuous peak only under exact symmetry. Finally, for a single bath with simultaneous diagonal and off-diagonal couplings, we demonstrate that a rotational transformation maps the system to an equivalent purely diagonal model, enabling simpler and intuitive physical interpretation and reduced computational complexity.

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