Direct Detection of sub-GeV Dark Matter

Direct Detection of sub-GeV Dark Matter

Introduction Input Output References


Dark matter in the sub-GeV mass range is a theoretically motivated but largely unexplored paradigm. Such light masses are out of reach for conventional nuclear recoil direct detection experiments, but may be detected through the small ionization signals caused by dark matter-electron scattering. Semiconductors are well-studied and are particularly promising target materials because their O(1 eV) band gaps allow for ionization signals from dark matter as light as a few hundred keV. The use of dark matter-electron scattering to detect sub-GeV dark matter has been successfully demonstrated in both xenon and silicon targets.

On this site, we provide Mathematica notebooks to calculate the dark matter-electron scattering rate in a variety of materials. For semiconductors (silicon, germanium) and scintillators (sodium iodide, cesium iodide, gallium arsenide), we use density functional theory to numerically calculate the rates, and have written a module for Quantum Espresso called QEdark. The calculation for xenon is simpler and does not require the use of QEdark. Instead, we use Hartree-Fock methods to compute the electronic wave functions. The results on this page can be used by both experimental collaborations and theorists to calculate their own sensitivities based on their specific setup.


To run QEdark yourself, you will need the following input files:


input files: Germanium (Ge), Silicon (Si)
Pseudopotentials: Germanium, Silicon
Dark Matter parameters: dm.Si.dat, dm.Ge.dat


input files: Sodium Iodide (NaI), Cesium Iodide (CsI), Gallium Arsenide (GaAs)
Pseudopotentials: Cesium, Iodide, Sodium, Gallium, Arsenide
Dark Matter parameters:,,


Integrated over a Maxwell-Boltzmann velocity distribution

The following is the output of QEdark for the form factor integrated over a Maxwell-Boltzmann distribution with v0=230 km/s, vesc=600 km/s, vearth=240km/s, and delta v=15 km/s. Included is a Mathematica notebook which analyzes the data and plots the cross-section reach vs. dark matter mass for Q=1-12, the recoil spectra, and the modulation rate.

Integrated form factors: Germanium Semicore Only, Germanium Valence Only, Silicon, NaI, CsI, GaAs
Analysis notebook: QEdark.nb

Unintegrated form factors

The following is the unintegrated form factor. The user will need to specify a dark matter velocity profile to calculate the expected rates.

Unintegrated form factors: Silicon, Germanium
Analysis notebook: QEdark-f2.nb


integrated form factors:
Analysis notebook: LDM_Xenon.nb


Contact: Tien-Tien Yu