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arXiv · 2608.25482

Parity-controlled electron-hole interference in exciton-phonon coupling

Michael O. Atambo
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Abstract

We demonstrate that exciton-phonon coupling in polar semiconductors is governed by a parity-controlled interference selection rule. By performing an exact multipole expansion of the excitonic form factor and validating it against numerical integration of hydrogenic envelope functions, we show that the long-range infrared divergence of the Fr\"ohlich interaction is exactly canceled for elastic scattering between excitonic states of the same parity. The ground-state exciton is thereby protected from long-wavelength polar phonons by destructive electron-hole interference. In contrast, transitions between states of opposite parity exhibit constructive interference, preserving a finite, robust coupling to macroscopic polar fields independent of band-structure details. Mass asymmetry between the electron and hole activates higher-order multipole terms in the elastic channel but leaves the constructive inelastic channel essentially unaffected. The selection rule is dimensionally invariant, applying to bulk and two-dimensional systems alike, and naturally explains the anomalously weak phonon dressing observed in halide perovskites as well as the strong phonon sidebands in transition-metal dichalcogenides. Our framework provides a universal, analytically exact criterion for exciton-phonon coupling strength, offering a design principle for engineering excitonic materials with tailored phonon interactions.

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Michael O. Atambo. 2026-08-26. Parity-controlled electron-hole interference in exciton-phonon coupling. https://arxiv.org/abs/2608.25482

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