A strategy for optimal material identification in solar dark photon absorption

TL;DR

This paper develops a theoretical framework to identify optimal detector materials for solar dark photon absorption, guiding future experiments in hidden-sector physics detection.

Contribution

It introduces a material-independent upper limit on absorption rates and assesses how different materials can approach this limit based on their plasma frequencies.

Findings

Derived an upper limit on dark photon absorption rates using Kramers-Kronig relations.

Identified conditions for materials to saturate the absorption rate limit.

Evaluated common detector materials and discussed tunable metamaterials for improved detection.

Abstract

Dark photons with masses in the 1-100 eV range can be produced in the Sun and subsequently absorbed in terrestrial detectors, offering a promising avenue for probing hidden-sector physics beyond the Standard Model. In this work, we develop a theoretically grounded strategy to identify optimal detector materials for solar dark photon absorption. Our strategy builds on a material-independent upper limit on the absorption rate, which we derive from Kramers-Kronig relations applied separately to the longitudinal and transverse dark photon modes. We show how the optimal material properties depend on the dark photon mass relative to the detector's plasma frequency, identifying the conditions under which a detector can saturate the theoretical upper limit. We then assess the performance of commonly used detector materials in light of these criteria and comment on the prospects of metamaterials featuring tunable plasma frequencies. Our results provide a general and model-independent framework to effectively guide the design of next-generation experiments targeting solar dark photons.