Many-body atomic response functions of xenon and germanium for leading-order sub-GeV dark matter-electron interactions in effective field theory

TL;DR

This paper provides comprehensive atomic response functions for xenon and germanium, crucial for interpreting sub-GeV dark matter-electron interactions, using advanced many-body physics methods and benchmarking against experimental data.

Contribution

It introduces a self-consistent relativistic random phase approximation approach to calculate atomic response functions, including spin-dependent effects, for dark matter detection.

Findings

Response functions agree with photoabsorption data within 5% errors.

Spin-dependent responses differ significantly from spin-independent ones.

Updated exclusion limits for dark matter interactions based on new data.

Abstract

Direct searches of dark matter candidates with mass energies less than 1 GeV is an active research field. The energy depositions are comparable to the scale of atomic, molecular, or condensed matter systems, therefore many-body physics plays an important role in understanding the detector's response in dark matter scattering. We present in this work a comprehensive data set of atomic response functions for xenon and germanium with 12.2 and 80 eV energy thresholds, respectively, using the (multiconfiguration) relativistic random phase approximation. This approach takes into account the relativistic, exchange, and correlation effects in one self-consistent framework, and is benchmarked successfully by photoabsorption data from thresholds to 30 keV with $\lesssim5\%$ errors. Comparisons with our previous and some other independent particle approaches in literature are made. It is also found that the spin-dependent (SD) response has significant difference from the spin-independent (SI) one such that the dark matter SD and SI interactions with electrons can be distinguished in unpolarized scattering, which is typical for direct search detectors. Finally, the exclusion limits set by current experiments are updated with our new results.