Dirac Materials for Sub-MeV Dark Matter Detection: New Targets and Improved Formalism

TL;DR

This paper explores Dirac materials as promising targets for detecting sub-MeV dark matter, introducing new candidate materials, refining detection formalism, and highlighting the potential for daily modulation signals to distinguish dark matter interactions.

Contribution

The study identifies two new Dirac materials, BNQ-TTF and Yb$_3$PbO, and improves the theoretical framework for dark matter detection using anisotropic Dirac materials.

Findings

BNQ-TTF and ZrTe$_5$ show strong daily modulation signals over 10%.

BNQ-TTF is highly sensitive to dark matter below 100 keV and 50 meV.

Yb$_3$PbO is more effective for heavier dark matter particles.

Abstract

Because of their tiny band gaps Dirac materials promise to improve the sensitivity for dark matter particles in the sub-MeV mass range by many orders of magnitude. Here we study several candidate materials and calculate the expected rates for dark matter scattering via light and heavy dark photons as well as for dark photon absorption. A particular emphasis is placed on how to distinguish a dark matter signal from background by searching for the characteristic daily modulation of the signal, which arises from the directional sensitivity of anisotropic materials in combination with the rotation of the Earth. We revisit and improve previous calculations and propose two new candidate Dirac materials: BNQ-TTF and Yb$_3$PbO. We perform detailed calculations of the band structures of these materials and of ZrTe$_5$ based on density functional theory and determine the band gap, the Fermi velocities and the dielectric tensor. We show that in both ZrTe$_5$ and BNQ-TTF the amplitude of the daily modulation can be larger than 10% of the total rate, allowing to probe the preferred regions of parameter space even in the presence of sizeable backgrounds. BNQ-TTF is found to be particularly sensitive to small dark matter masses (below 100 keV for scattering and below 50 meV for absorption), while Yb$_3$PbO performs best for heavier particles.