title: Competition between diagonal and off-diagonal coupling gives rise to charge-transfer states in polymeric solar cells.
abstract: It has long been a puzzle on what drives charge separation in artificial polymeric solar cells as a consensus has yet to emerge among rivaling theories based upon electronic localization and delocalization pictures. Here we propose an alternative using the two-bath spin-boson model with simultaneous diagonal and off-diagonal coupling: the critical phase, which is born out of the competition of the two coupling types, and is neither localized nor delocalized. The decoherence-free feature of the critical phase also helps explain sustained coherence of the charge-transfer state. Exploiting Hamiltonian symmetries in an enhanced algorithm of density-matrix renormalization group, we map out boundaries of the critical phase to a precision previously unattainable, and determine the bath spectral densities inducive to the existence of the charge-transfer state.
authors.affiliation: State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.|Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore.|Department of Physics, Hangzhou Normal University, Hangzhou 310036, China.
authors.forename: Nengji
authors.initials: N
authors.lastname: Zhou
authors.affiliation: Departamento de Física Aplicada, Universidad Politécnica de Cartagena, Cartagena 30202, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Prior
authors.affiliation: Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao