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This study advances the modeling of light-harvesting assemblies by moving beyond the point-dipole approximation to incorporate finite geometry and local transition dipoles via a non-Hermitian Hamiltonian. The analysis reveals that unit-cell symmetry in purple bacteria inverts bright-dark state ordering, effectively making the entire crystal the primary energy-harvesting entity rather than isolated subunits. These findings provide a more rigorous theoretical framework for understanding quantum electrodynamic effects in biological systems, which could inform the design of next-generation bio-inspired photonic devices.
Collective Emission in LH2 Assembly Beyond the Point-Dipole Approximation
arXiv:2606.11227v1 Announce Type: cross Abstract: Collective emission in light-harvesting assemblies is governed by the local transition dipole and finite geometry of emitting units, a fact that point-dipole approximation obscures. To go beyond this picture, we develop a non-Hermitian Hamiltonian using the quantum electrodynamic dyadic Green's tensor for a purple bacteria. We construct it for the isolated 24-bacteriochlorophyll conical frustum and its P42$_1$2 crystallographic assembly. The P42$_1$2 unit-cell symmetry is found to invert the bright-dark ordering of the single ring, placing subradiant states at the low-energy end and revealing the entire crystal to be the energy-harvesting entity. Tilt-driven switching is activated only in crystal geometries where the finite dipole-carrier (LH2) lies perpendicular to the growth plane. Vacancy and orientational disorder work only in cooperation to renormalize the switching threshold from higher polar angles to lower values.
Abstract:Collective emission in light-harvesting assemblies is governed by the local transition dipole and finite geometry of emitting units, a fact that point-dipole approximation obscures. To go beyond this picture, we develop a non-Hermitian Hamiltonian using the quantum electrodynamic dyadic Green's tensor for a purple bacteria. We construct it for the isolated 24-bacteriochlorophyll conical frustum and its P42$_1$2 crystallographic assembly. The P42$_1$2 unit-cell symmetry is found to invert the bright-dark ordering of the single ring, placing subradiant states at the low-energy end and revealing the entire crystal to be the energy-harvesting entity. Tilt-driven switching is activated only in crystal geometries where the finite dipole-carrier (LH2) lies perpendicular to the growth plane. Vacancy and orientational disorder work only in cooperation to renormalize the switching threshold from higher polar angles to lower values.
Biological Physics (physics.bio-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Chemical Physics (physics.chem-ph); Quantum Physics (quant-ph)
arXiv:2606.11227 [physics.bio-ph]
(or arXiv:2606.11227v1 [physics.bio-ph] for this version)
Full text under the publisher's open licence · 152 words